Microcystins in potable surface waters: toxiceffects and removal strategiesAmber F. Roegnera, Beatriz Brenab, Gualberto González-Sapienzab

and Birgit Puschnera*

ABSTRACT: In freshwater, harmful cyanobacterial blooms threaten to increase with global climate change and eutrophicationof surface waters. In addition to the burden and necessity of removal of algal material during water treatment processes,bloom-forming cyanobacteria can produce a class of remarkably stable toxins, microcystins, dif!cult to remove from drinkingwater sources. A number of animal intoxications over the past 20 years have served as sentinels for widespread riskpresented by microcystins. Cyanobacterial blooms have the potential to threaten severely both public health and theregional economy of affected communities, particularly those with limited infrastructure or resources. Our main objectiveswere to assess whether existing water treatment infrastructure provides suf!cient protection against microcystin exposure,identify available options feasible to implement in resource-limited communities in bloom scenarios and to identify strate-gies for improved solutions. Finally, interventions at the watershed level aimed at bloom prevention and risk reduction forentry into potable water sources were outlined. We evaluated primary studies, reviews and reports for treatment optionsfor microcystins in surface waters, potable water sources and treatment plants. Because of the dif!culty of removal ofmicrocystins, prevention is ideal; once in the public water supply, the coarse removal of cyanobacterial cells combined withsecondary carbon !ltration of dissolved toxins currently provides the greatest potential for protection of public health.Options for point of use !ltration must be optimized to provide affordable and adequate protection for affected communi-ties. Copyright © 2013 John Wiley & Sons, Ltd.

Keywords: Microcystins; cyanotoxins; intoxications; potable water sources; eutrophication; water treatment plants; interventions;resource poor

IntroductionIncreasing global water temperatures, nutrient and pollutantenrichment via anthropogenic runoff, drought and !ooding leadto eutrophication of fresh and coastal water bodies and canresult in toxicogenic cyanobacterial blooms (Newcombe et al.,2012; Paerl and Paul, 2012). In 1878, Francis described intoxica-tion of farm stock from ingestion of surface scum at LakeAlexandrina, a freshwater lake at the mouth of the Murray Riverin South Australia near Adelaide. The ingestion of wind-blowncyanobacteria Nodularia spumigena resulted in the death ofsheep, horses, dogs and pigs within 1–24 h (Francis, 1878). Sincethis "rst documented case description of a cyanobacterialpoisoning, a wide array of animal intoxications have beenreported, in addition to the identi"cation of numerouscyanobacterial genera and species capable of producing diverseneurotoxins, hepatotoxins, gastrointestinal toxins and skin irri-tants (Chorus et al., 2000; Stewart et al., 2008a). Table 1 catalogsall identi"ed human and animal cases linked to microcystin (MC)intoxication. MCs represent a family of potent liver toxins andare considered the most resistant of cyanotoxins to degradationbecause of their stable cyclic peptide structure. Acute andchronic effects of MCs are not completely understood as theycan exhibit diverse system effects in vivo and diverse mecha-nisms in vitro (Dawson, 1998; Gehringer, 2004). With over 100congeners identi"ed and named according to variable aminoacids positions (Fig. 1) (Rinehart et al., 1994; Bateman et al.,1995), MCs inhibit protein phosphatases leading to acute liverfailure (Falconer, 2008). The most consistently identi"ed MC,

MC-LR (abbreviated for common amino acids leucine andarginine at positions 2 and 4, respectively)(Carmichael et al.,1988), is also believed to be the most potent congener.However, the World Health Organization (WHO) provisionalguideline of 1 !g l–1 for surface waters is speci"c for MC-LRbecause of lack of data with respect to other congeners.Recently, preferential uptake of other congeners into organsystems has raised concern (Feurstein et al., 2011; Trinchetet al., 2013) about risk presented by congeners with variablehydrophobicity, including more commonly monitored MC-RR(arginine at positions 2 and 4), MC-LA (leucine and alanine,respectively), MC-YR (tyrosine and arginine) and more hydro-phobic variants, MC-LF (leucine and phenylalanine) and MC-LW(leucine and tryptophan). The latter hydrophobic variants havedemonstrated increased cell permeability and cytotoxicity(Vesterkvist et al., 2012). Animal intoxications have been linkedto other congeners, suggesting risk may be underestimatedwhen water is solely monitored for MC-LR (Stewart et al., 2008b).

*Correspondence to: Birgit Puschner, Department of Molecular Biosciences,School of Veterinary Medicine, 1089 Veterinary Medicine Drive, University ofCalifornia, Davis, CA 95616, USA. Email: bpuschner@ucdavis.edu

aDepartment of Molecular Biosciences, School of Veterinary Medicine, Universityof California, Davis, CA, 95616, USA

bCátedra de Inmunología, Facultad de Química y Facultad de Ciencias,Universidad de la República, Instituto de Higiene, Montevideo, Uruguay

J. Appl. Toxicol. 2013 Copyright © 2013 John Wiley & Sons, Ltd.

Review Article

Received: 11 June 2013, Revised: 16 July 2013, Accepted: 17 July 2013 Published online in Wiley Online Library

(wileyonlinelibrary.com) DOI 10.1002/jat.2920

Table1.

Repo

rted

andcon!

rmed

anim

alintoxicatio

nswith

MCvaria

nts.Includ

esrepo

rtsin

peer

review

edliteraturein

which

human

oran

imalillne

sswas

repo

rted

andcoincide

dwith

atleastminim

umcon!

rmationof

MCpresen

cein

water

source

oreviden

ceof

hepa

tocellularinjury

inmou

sebioa

ssay

Affe

cted

species

Locatio

nYe

arClinical

sign

san

dhistory

Diagn

ostic

parametersan

dresults

Citatio

n

Dog

Lake

Amstelmeer,

TheNethe

rland

sFall20

113do

gs:swim

mingin

lake,v

omiting

,lethargy

,dif!

culty

breathing,

sign

sof

abdo

minal

pain,g

astrointestin

albleeding

,death

with

in24

h

17to

2.92

!10

3!g

l–1totalM

Cin

lake

water

with

surfa

cescum

,con

taining

upto

5.27

!10

3!g

g–1dw

MC;

94!g

g–1dw

MCfoun

din

vomit

Lurling

and

Faassen,

2013

Dog

MilfordLake,

Kansas,U

SASu

mmer

2011

Fulm

inan

tliver

failure

and

coag

ulo-

pathy;acute,massive

hepa

ticne

cro-

sisan

dhe

morrhag

e,ne

crosisof

the

rena

ltub

ular

epith

elium

12600

0ng

ml–1MCs

inlake

water;

con!

rmation

ofMCs

invo

mitu

san

dliver

vande

rMerwe

etal.,20

12

Roede

er(Cap

reolus

capreolus)

Grim

stad

,Norway

Octob

er20

00Stup

orou

san

imal,u

nrespo

nsive,

weakwith

!ne

musclefasciculations,

liver

lesion

scompa

tible

with

MC

intoxicatio

n

1361

ngg–

1MCs

inliver

(wet

weigh

t);

!eldinspectio

nof

draina

geditch

inmeado

w

Han

deland

and

Osten

svik,2

010

Dog

WaitakiRiver,

New

Zealan

dNov

embe

r20

08Acute

deathafteringe

stion

Isolated

!lamen

tous

cyan

obacteriu

mPh

ormidium

sp.;16

07mgkg

–1MCs

inextract;consistent

patholog

y

Woo

det

al.,20

10

Southe

rnsea

otters

Mon

tereyBa

y,CA

,USA

2007

11seaotters:lesions

sugg

estiveof

liver

failure:icteric,enlarged,bloo

dy,friable

LiverMC-RR

from

1.97

to104.46

ppb

wet

weigh

t,liver

MC-LR

was

348

ppbwetweigh

t;consistent

grossp

a-tholog

y!nd

ings;suspe

cted

bivalve

inge

stion

Miller

etal.,20

10

Hum

an(w

ater

skier)

Salto

Grand

eDam

,Argen

tina

Janu

ary

2007

Youn

gmalewater

skierfellin

bloo

mwater,

4h

develope

dna

usea,

abdo

minal

pain

andfever.3da

yslater,dyspneaandrespiratorydistress

and

!nally

atypical

pneumon

ia.20

dayrecovery

48.6

!gl–1of

MC-LR

was

detected

inwater

samples;

patie

ntshow

edmarkedly

elevated

serum

liver

enzymes

Giann

uzzi

etal.,20

11

Child

ren

(chron

icexpo

sure)

ThreeGorge

sRe

servoirRe

gion

,Ch

ina

2005

–200

9MCconcen

trations

indrinking

water

aqua

ticfood

(carpan

ddu

ck)from

two

lakes

and

four

wells;13

32childrenag

es7–15

weretested

for

liver

enzymean

dserum

MClevels

Epidem

iologicstud

y:child

ren

using

lake

water

sourceswith

thehigh

est

MCconcen

trations

hadatotale

sti-

mated

daily

MCintake

of2.03

!gan

dha

dsign

i!cantly

high

erAST,

ALP

levels.

Liet

al.,20

11

Meg

aherbivo

res

Nhlan

ganzwan

eDam

,Kruge

rNationa

lPark,

SouthAfrica

Februa

ryto

July20

05Eu

trop

hicatio

nof

watersfrom

fecal

material

TotalMC

levelof

2371

8!g

l–1in

water;toxin

detectionin

tissues

ofmeg

aherbivo

res

Obe

rholster

etal.,20

09

Freshw

ater

terrap

ins:

Emys

orbicularis,

Mau

remys

leprosa

Lake

Oub

eira,

Algeria

Octob

er20

0512

freshw

ater

terrap

inswerefoun

dde

adin

asm

alla

rea(0.5

ha)

1192

.8!g

MC-LR

equivalent

g–1dw

inliver

tissue

inM.leprosa

and

37.19!g

MC-LR

equivalent

g–1dw

Nasriet

al.,20

08

A. F. Roegner et al.

J. Appl. Toxicol. 2013Copyright © 2013 John Wiley & Sons, Ltd.wileyonlinelibrary.com/journal/jat

Table1.

Continue

d

Affe

cted

species

Locatio

nYe

arClinical

sign

san

dhistory

Diagn

ostic

parametersan

dresults

Citatio

n

inthevisceraof

E.orbicularis;1

.12

mg

MC-LR

equivalentsg–

1dried

bloo

mmaterial

Fish,

herbivou

rous

birds,

piscivorou

sbirds

LosAnsares

Lago

on,

Doñ

anaNationa

lPa

rk,Spa

in

July20

04Massmortalityof

herbivorou

swater-

fowl,thou

sand

sof

!sh

and

later

thou

sand

sof

piscivorou

sbirds

with

in2-week

perio

dfollowing

bloo

m

Abun

dant

toxinprod

ucingMicrocystis

aerugino

sa;mou

sebioa

ssay

with

cyan

obacteria

lextract;toxinde

tec-

tion

in!sh

livers,

bird

crop

san

dlivers

Lope

z-Ro

das

etal.,20

08

Hum

ans

(chron

icexpo

sure)

CentralS

erbia

(Top

licki,N

iski,

andSu

mad

ijski

region

s)

1980

–199

0,20

00–2

002

Extrem

elyincreasedincide

nceof

pri-

maryliver

cancer

inregion

sof

cen-

tral

Serbia

depe

nden

tup

onreservoirs

affected

byhe

avy

cyan

obacteria

lbloo

msrelativ

eto

those

region

sun

affected

bybloo

ms

650MC-LR

!gl–1in

CélijeRe

servoir

while

2.5!g

l–1foun

din

Kru!evac

town-supp

liedtapwater;inciden

ceratesof

prim

aryliver

cancer

inre-

gion

swith

affected

reservoirscom-

pared

tothose

with

unaffected

reservoirs

Svircev

etal.,20

09

Flam

ingo

chicks,

othe

rwaterfowl

Luciode

las

Pied

rasLago

on,

Doñ

anaNationa

lPa

rk,Spa

in

July20

01Massmortality(atleast57

9birds)co-

occurred

with

appe

aran

ceof

cyan

obacteria

lbloom

Cyan

obacteria

inwater

andcrop

ofaffected

birds:

sign

i!cant

toxin

concen

trations

incrop

san

dliver

ofexpo

sed"am

ingo

s

Alonso-

And

icob

erry

etal.,20

02

Hum

ans

(chron

icexpo

sure)

Florida,USA

1981

–199

8Ep

idem

iologicstud

ylin

king

hepa

to-

cellularcarcinom

aincide

nce

with

reside

nce

with

inclose

proxim

ityto

asurfacewater

treatm

entplan

t

Mon

itorin

gsurvey

forcyan

obacteria

andtoxins

insurfacewater

drink-

ing

sources;

Geo

grap

hicInform

a-tio

nSystem

toevalua

terisk

ofhe

patocellularcarcinom

aan

dprox-

imity

tosurfa

cewater

treatm

ent

plan

t

Flem

ing

etal.,20

02

Hum

ans

(acute

expo

sure)

Caruara,Brazil

Februa

ry19

9611

6of

130pa

tientsat

rena

ldialysis

facility:

nausea,

vomiting

,acute

liver

failure,

death

inov

er50

patie

nts

Elevated

serum

conjug

ated

bilirub

in,

and

serum

aspa

rtate

aminotrans-

ferase;d

etectio

nof

MCs

indialysis

source

water;M

Cscon!

rmed

intis-

sues

andserum

ofpa

tients

Jochim

sen

etal.,19

98

Ducks

Pond

(Shin-ike),

Nishino

miya,

Hyo

goPrefecture,

Japa

n

1995

20spot-billed

ducks:un

naturald

eath

inpo

ndwith

bloo

m;birdsun

af-

fected

inne

ighb

oring

pond

with

bloo

m

Shin-ikepo

nd:318

!gg–

1MC–

RRan

d16

1!g

g–1MC-LR.Oo-ike

pond

with

node

aths:29

!gg–

1MC-RR

andno

detectab

leMC-LR

Matsuna

gaet

al.,19

99

Hum

ans

(chron

icexpo

sure)

Haimen

city,

Jian-Su

prov

ince

andFu

suicou

nty,

Gua

ngxiprov

ince,

China

1993

–199

4Ep

idem

iologic

correlation

betw

een

MC

presen

tin

pond

–ditch

water

and

incide

nce

ofprim

ary

liver

cancer

ELISAde

tectionof

MCs

inpo

ndditch

water,con

!rm

ationwith

mou

sebio-

assay

intumor

prom

otion,

meta-

analysis

ofincide

nce

ofprim

arily

liver

cancer

inrelatio

nto

ditchwater

Yuet

al.,20

01

(Con

tinues)

Persistence of microcystins in drinking water

J. Appl. Toxicol. 2013 Copyright © 2013 John Wiley & Sons, Ltd. wileyonlinelibrary.com/journal/jat

Table1.

Continue

d

Affe

cted

species

Locatio

nYe

arClinical

sign

san

dhistory

Diagn

ostic

parametersan

dresults

Citatio

n

Cattle

Southe

rnCo

lorado

,USA

1997

24he

ifers:acutede

ath,weak,anorectic,

andhype

rsen

sitiveto

noise

anddied

with

in3da

ysafterthe

onseto

fsigns

Blue

–green

alga

efoun

din

rumen

;large,

friable,

and

dark

red

liver;

mou

sebioa

ssay

with

bloo

mextract;Microcystisspeciesan

dMC-LR

detected

Puschn

eret

al.,19

98

Cattle,she

epDam

sin

Western

Cape

Prov

ince,

SouthAfrica

?3ou

tbreaksin

cattleandsheep:

acute

mortalityfollowed

byph

otod

ermatitis

insurvivinganimals

Hep

atotoxicity

con!

rmed

byi.p.

administration

ofwater

tomice;

con!

rmationof

presen

ceof

MC-LR

inthird

outbreak

VanHalde

ren

etal.,19

95

Dog

stag

nant

tidepo

ol,

CA,U

SANov

embe

r19

90Inge

stionof

concen

trated

alga

lmate-

rial,

vomiting

,diarrhea,lethargy,

liver

failure

Large,

friab

lean

dda

rkredliver

with

hepa

tocyte

dissociatio

n,de

gene

ra-

tion

and

necrosis;po

sitiv

emou

sebioassay

ofinjected

bloo

mmaterial

DeV

ries

etal.,19

93

Hum

ans(soldiers)

(acute

expo

sure)

Staffordshire

,En

glan

dSeptem

ber

1989

2soldiers:pn

eumon

iain

two

16-year-o

ldarmyrecruitsafterfalling

into

bloo

mwater

durin

gcano

eexercises,later8soldiers

with

addi-

tiona

lsym

ptom

s

MC-LR

iden

ti!ed

byhigh

-perform

ance

liquid

chromatog

raph

y;liver

dam-

agean

dacutepu

lmon

arythrombo

-sisin

mou

sebioa

ssay

with

bloo

m(M

icrocystis

aerugo

nisa);

additio

nal

8soldiers

had

sore

throats,

head

-ache

s,ab

dominalpa

ins,drycoug

hs,

diarrhea,vo

miting

and

blistered

mou

ths

Turner

etal.,19

90

Dog

san

dge

ese

Echo

Lake,

Saskatchew

an,

Cana

da

June

1959

Dog

san

dge

esewith

contacttoalga

lmaterialb

lownto

near

shore,

died

sudd

enly

Autopsyshow

edsign

sof

liver

cong

es-

tion,

in"am

mation

and

edem

aof

thelung

san

dhe

morrhag

icin"am

-mation

ofintestine;

colonies

ofMicrocystis

and

Anaebena

,mou

sebioassay

with

hepa

ticcong

estio

n

Dillen

berg

and

Deh

nel,19

60

Hum

ans,cows

GullLake,

Long

Lake,

Echo

Lake,

BuffaloPo

und

Lake

Saskatchew

an,

Canada

July19

59Multip

lehu

man

expo

sures,includ

ing

10childrenat

campan

dph

ysician

bathed

inalga

ecoveredlake

water,

acutediarrhea,vom

iting

;cattle

died

aftera

cute

inge

stion

Iden

ti!catio

nof

cyan

obacterialspe

cies

inlake

water;b

loom

collected

from

lake

con!

rmed

bymou

sebioassay

Dillen

berg

and

Deh

nel,19

60

dw,d

ryweigh

t;LR,aminoacidsleucinean

darginine

atpo

sitio

ns2an

d4;

MC,

microcystin;R

R,arginine

atpo

sitio

ns2an

d4.

A. F. Roegner et al.

J. Appl. Toxicol. 2013Copyright © 2013 John Wiley & Sons, Ltd.wileyonlinelibrary.com/journal/jat

Mechanism of Action

Acutely, MCs cause severe gross hepatomegaly with progressivecentrilobular hepatocyte necrosis, rounding and dissociation. Thebreakdown of the sinusoidal endothelium results in intrahepatichemorrhage and rapidly ensuing death (Hooser et al., 1989,1991; Hooser, 2000).

Uptake of these macrocyclic compounds into hepatocytesoccurs via organic anion transport polypeptides (OATPs) (Monkset al., 2007; Fischer et al., 2010) and the widespread expressionof these transporters allows for uptake into numerous otherorgan systems (Feurstein et al., 2009; Kalliokoski and Niemi,2009; Bednarczyk, 2010). Inside the hepatocyte, MCs potentlyinhibit protein phosphatase 1 and 2A, resulting in cytoskeletaldisruption and rearrangement of associated !lamentous actin,resulting in the morphological changes noted (Runnegar et al.,1991, 1995; Guzman et al., 2003). The unusual bulky side chaincommon to all MCs (ADDA) (Fig. 1) is crucial for the Michaeladdition to cysteine residues of PP1 and PP2A (Dawson, 1998).MCs also induce apoptosis through free radical formation andmitochondrial alterations (Ding et al., 1998; Ding and Nam,2003). A single dose i.v. in rats resulted in an increase in liversphingolipid, implicating ceramide-mediated apoptosis, a dose-dependent decrease in PP2A expression, and a dose-dependentdecreased expression of Bcl2 family proteins, involved in cellcycle/apoptosis regulation (Billam et al., 2008). Toxic effect mayultimately depend upon the ability of antioxidant pathways tocounteract oxidative damage (Jayaraj et al., 2006, 2007; Xionget al., 2009). Furthermore, as tumor-promoting compounds,MCs, through dysregulation of phosphorylation, may result inpromotion of proto-oncogenes, while MCs also induce DNAdamage in hepatocytes along with other cell lines (Zeguraet al., 2003, 2008).

Pharmacokinetics/toxicokinetics

Despite the abundant literature on MCs, the understanding ofpharmacokinetics remains limited, particularly with regard tospecies differences and little data accounts for variation amonguptake of various congeners. The majority of studies havebeen conducted on mice with i.v. or i.p. administration ofcyanobacteria, !ltrates or puri!ed MCs. Following i.v. and i.p.administration in rodents, MCs are rapidly distributed to the liver

and plasma half-lives of MC-LR in mice i.v. administration were0.8 and 6.9 min for the alpha and beta phases of elimination(Robinson et al., 1991). The study also indicated that 9 and14% of the dose was excreted in urine and feces, respectively,after 12 h, with 60% of it being excreted unchanged. Studies inswine have also indicated the majority is excreted unchanged,with only two metabolites detected (Stotts et al., 1997a,1997b). Glutathione and cysteine conjugation are thought tobe major detoxi!cation pathways, but the exact route of metab-olism has yet to be de!ned (Kondo et al., 1996; P"ugmacheret al., 1998). Further work on bioavailability for MC congenersis needed to evaluate risk from oral ingestion. Absorption occursin the small intestine and then MCs are rapidly distributed to theliver, but also reach the lung, heart and capillaries (Ito et al.,2000). The kidney appears important for excretion (Wang et al.,2008), while OAT1B1 and OATP1B3 appear to be crucial foruptake into the liver (Seithel et al., 2007). Adsorption of MCsvia the respiratory route is possible and can result in damageto nasal epithelium at low doses (Benson et al., 2005) and deathat high intratracheal exposures (Ito et al., 2001).

Toxic Dose

LD50s for MCs vary between 50 !g kg–1 and 11 mg kg–1, variablecongener, species and route of administration. In mice, the oralLD50 value for MC-LR is 10.9 mg kg–1, whereas the i.p. LD50 is50 !g kg–1. As a single bloom may contain numerous MCcongeners, the toxic dose becomes dif!cult to estimate. Theno-observed adverse effect level in liver pathology for orallyadministered MC-LR to mice is 40 !g kg–1 day–1 (Fawell et al.,1994), while the lowest observed adverse effect level for orallyadministered MC-LR is 100 !g kg–1 day–1 in pigs (Falconer andHumpage, 2005) and 50 !g kg–1 day–1 in rats (Heinze, 1999).The WHO has set the tolerable daily intake for human ingestionof MC LR at 0.04 !g kg–1 day–1 (Kuiper-Goodman et al., 1999) byapplying an uncertainty factor of 1000 (100 for intra- andinterspecies variations, 10 for limitations in data, particularly withregard to chronic toxicities and carcinogenicity) based on the13-week no-observed adverse effect level study described abovefor oral administration (Fawell et al., 1994). The concurrentprovisional guideline of total MC-LR in drinking water was deter-mined from the no-observed adverse effect level in mice with a0.8 factor of daily exposure from drinking water and rounding to1 !g l–1. The value was supported by the 44-day lowest observedadverse effect level study in pigs exposed to MC-LR in drinkingwater described above. All guidelines remain provisionalbecause of the limited data regarding congeners and chroniceffects; globally, there is a need to improve guidelines andmonitoring strategies for all freshwater cyanotoxins, includingMCs (Burch, 2008).

Clinical Signs and Diverse Effects

MC intoxication in wildlife, livestock and domestic animals mustbe considered in cases of acute hepatotoxicosis with clinicalsigns of diarrhea, vomiting, weakness, pale mucous membranesand shock, most particularly when access to cyanobacterialbloom source is identi!ed. The majority of animals die within afew hours of exposure with no known antidote, but someanimals may live for several hours and develop hyperkalemia,hypoglycemia, nervousness, recumbency and convulsions. Noknown treatments exist although preliminary work suggests

Figure 1. The chemical structure of microcystin with amino acidsleucine and arginine at positions 2 and 4. (1) D-alanine; (2) L-leucine; (3)D-methylaspartic acid; (4) L-arginine; (5) 3-amino-9-methoxy-2,6,8-trimethyl-10-phenyldeca-4,6-dienoic acid (Adda); (6) D-glutamic acid;(7) N-methyldehydroalanine. The variable amino acids at positions (2)(L-leucine) and (4) (L-arginine) designate the name of the congener.Microcystin-amino acids leucine and arginine at positions 2 and 4 isthe commonly found and most commonly tested congener.

Persistence of microcystins in drinking water

J. Appl. Toxicol. 2013 Copyright © 2013 John Wiley & Sons, Ltd. wileyonlinelibrary.com/journal/jat

potential prophylactic administration of competitive substratesfor OATP (rifampicin, cyclosporine) or antioxidants (glutathione,silymarin, vitamin E, selenium and green tea polyphenols).Cattle having survived acute intoxication may develop hepaticphotosensitization. In addition, nephrotoxic and cardiotoxiceffects have been described in chronic administration inlaboratory animals (Milutinovic et al., 2002, 2003, 2006; Suputet al., 2010), while immune suppression and neurotoxic ef-fects have been implicated in vitro (Chen et al., 2004; Fischeret al., 2005; Feurstein et al., 2009). In humans, primary liverand colorectal cancer has been associated with prolongedexposure to MC-contaminated drinking water in China andTaiwan (Zhou et al., 2002), while subchronic exposure i.p. ofMC-LR (20 !g kg–1) causes the appearance of hepatic nodules(Ito et al., 1997).

Persistence in Surface Waters

Many of the source bodies of water of exposure for animalintoxications described in Table 1 also serve human populations.While animals tend to ingest bloom material either directly orthrough grooming concentrated mats on their coats or skin,the blooms also pose a risk to people through recreationalactivities (accidental ingestion through submersion or inhala-tion) and entry into drinking water reservoirs. MCs largelyremain intracellular in healthy and young cyanobacterialpopulations, enabling coarse removal of algal material. However,conditions present in particularly eutrophic systems result in celllysis and extracellular concentrations several orders of magni-tude higher than guidelines recommended by the WHO(Sivonen, 1996). Multiple cyanobacteria in fresh and brackishwaters around the world produce MCs; these surface watersoften supply potable water for communities and challengemany commonly employed treatment options (Hitzfeld et al.,2000; Westrick et al., 2010; de la Cruz et al., 2011). MCs persistin the environment for weeks after a bloom (Pearson and Neilan,2008). The generic cyclic seven amino acid MC results in aremarkably stable compound from pH 1 to 9, across tempera-tures (t"=3 weeks at pH 1 and 40 °C) (Harada et al., 1996) andsalinities (Mazur and Pliñski, 2001). The structure resists degra-dation by boiling, while oxidation requires higher oxidantconcentrations than those typically used and can result intoxic degradation products. Because of this environmentalpersistence, more routine monitoring of domestic and wildlifespecies for both toxicoses and exposure, particularly in thevicinity of surface waters used by humans for source drinkingwater, may be warranted to reduce risk of acute or chronicexposures in human populations.

Documented Human Exposures

Limited acute human intoxications have been linked directly toMC exposure. In the mid- to late 1900s, there was increasingawareness about potentially toxicogenic cyanobacterial bloomsin recreational waters. A series of case investigations in 1959 inSaskatchewan linked acute toxicoses in dogs, birds, horses andcattle to exposure to the now known MC-producing speciesand followed up with mouse bioassays with i.p. injection ofcyanobacterial bloom water resulting in similar necropsy !nd-ings (Dillenberg and Dehnel, 1960). Several human cases ofacute gastroenteritis, including eight children at camp, were alsodescribed following recreation in said water bodies. Of particular

concern, Buffalo Pound Lake, a major water supply for the areacontained a Microcystis bloom that reportedly had resulted inacute deaths in cows and dogs (Dillenberg and Dehnel, 1960).Although no test was developed at the time for MCs speci!cally,a mouse bioassay with source water yielded marked hepaticcongestion. These accounts were among the !rst, and remainamong the few, to document human and animal co-exposures.As animals frequently ingest water from source water bodiesfrom which municipal water is drawn, more vigorous monitoringof animals in these regions is warranted, particularly giventhe dif!culty in removal from drinking water. In 1989, two19-year-old army recruits fell into and swallowed cyanobacterialbloom water in Staffordshire, England during routine canoeexercises; the youngmen developed acute pneumonia, alongwithgastrointestinal signs (Turner et al., 1990). To our knowledge, thisintoxication was the !rst in which MC was positively identi!ed inthe water source.

In February 1996, over 100 patients developed acute liverfailure at a hemodialysis center in Caruaru, Brazil (Azevedoet al., 2002) when patients received water from a contaminatedreservoir. Chlorine treatment of the trucked water from a localreservoir with a toxin-producing bloom resulted in lysis and highextracellular levels of MCs inadequately removed by coarse andactivated carbon !ltration at the clinic (Pouria et al., 1998;Hilborn et al., 2007). At least 52 deaths ensued because ofexposure. This tragic case greatly shifted attention toward therecognition of the serious toxicity potential of these blooms,the development of international guidelines, and the increasedeffort for detection methods (Gorchev and Ozolins, 1984; Choruset al., 2000; de Figueiredo et al., 2004; Burch, 2008).

In January 2007, an acute exposure was documented in ayoung water skier who fell into a bloom at Salto Grande Dam,Argentina, where levels of 48.6 !g l–1 of MC-LR were laterdetected. The accidental ingestion resulted in nausea, abdomi-nal pain and fever, followed by dyspnea and respiratory distress3 days later (Giannuzzi et al., 2011). Epidemiological studies havedemonstrated adverse health effects linked to recreationalexposure in the USA (Backer et al., 2008; Backer et al., 2010)and chronic outcomes such as hepatocellular carcinoma andprimary liver cancer from persistent low levels in drinking waterin China (Yu et al., 2001; Li et al., 2011) Serbia, (Svircev et al.,2009) and even Florida (Fleming et al., 2002). Exposures are likelyunderestimated because of the dif!culty and expense ofmultiple congener toxin detection (McElhiney and Lawton,2005; Msagati et al., 2006; Pearson and Neilan, 2008; Sivonen,2008; Humbert, 2010) and compounding factors that alsocause disease (Ahmed et al., 2007). The WHO designates aprovisional guideline of 1.0 !g l–1 for total MC-LR (extracellularand intracellular) in drinking water. Recent data have docu-mented naturally occurring extracellular concentrations exceed-ing this recommendation even following treatment (Lahti et al.,2001a; Blaha and Marsalek, 2003; Gurbuz et al., 2009). Resource-limited communities often depend directly on water sourceswith limited treatment infrastructure available, and low cost,point-of-source treatment options become critical for adequateprotection of human health. Wildlife and domestic animalspecies may provide sentinels for concurrent human exposure(acute or chronic). We reviewed the state of knowledgeconcerning ef!cacy of existing treatment strategies, promisingareas for expanded investigations, and strategies for manage-ment of reservoirs or watersheds for prevention and expeditingin situ removal.

A. F. Roegner et al.

J. Appl. Toxicol. 2013Copyright © 2013 John Wiley & Sons, Ltd.wileyonlinelibrary.com/journal/jat

Table2.

Overview

oftreatm

entop

tions

forMCremov

alfrom

potablewater

sources

Treatm

entop

tions

Stag

eProv

enmeasures

Specialcon

side

ratio

nsRe

levant

citatio

ns

Preven

tion

Watershed

Decreasenu

trient

load

ing;

enha

nce

unde

rstand

ingof

watershed

Implem

entatio

nof

barriers

tonu

trient

inpu

ts(con

structed

wetland

s,wastewater

treatm

entplan

ts);de

creaseduseof

nitrates/pho

spha

tes;increasedmon

itorin

gto

unde

rstand

riskof

toxinprod

uctio

nby

localb

loom

s

Codd

,20

00;Pa

erlan

dPa

ul,

2012

;Sm

ith,

2003

;Woo

det

al.,20

11

Photod

egrada

tion

Watershed

UVA

andph

otosyn

theticallyactiv

eradiationmosteffectivewavelen

gths;

effectivein

shallow

surfacewatersor

wellm

ixed

thin

layers

Effectiven

essvarie

swith

type

ofirrad

iatio

n,de

pthan

dclarity

ofwater

column,

inhibitors

orcatalystsof

degrad

ation

(NOM,b

loom

extractan

dpigm

ents)

Tsujiet

al.,19

95;Welkeran

dSteinb

erg,

2000

;Wormer

etal.,20

10

Microbial

degrad

ation

Watershed

Evalua

telocalw

ater

source

forna

turally

occurringbio!

lms;capa

bleof

MC

degrad

ation(BiologMT2

enzymaticassay);

bio!

lmform

ationen

hances

remov

alin

situ

Limite

dnu

mbe

rof

speciesiden

ti!ed

asMC

degrad

ers;may

existread

ilyin

freshw

aters;

potentialp

lantingof

aqua

ticplan

tsto

enha

ncebio!

lmform

ationan

dup

take

remov

althem

selves

Chen

etal.,20

08;E

leuterio

and

Batista,20

10;Man

ageet

al.,

2010

;Maruy

amaet

al.,20

03;

Nim

ptsch

etal.,20

08;Saito

etal.,

2003

;Sh

imizu

etal.,

2011

Bank

!ltration

Watershed

Characterizelocalw

ater

andsoil

characteristicsin

benchtopstud

ies;

remov

alisacombina

tionof

adsorptio

nan

dmicrobial

degrad

ation

De!

neMCde

grad

ationpo

tentialo

flocal

soilcommun

ity;p

airwith

insitustud

iesto

determ

ineho

wto

best

design

collection

ofpo

tablewater

Dillon

etal.,20

02;G

rutzmache

ret

al.,

2002

;Lahti

etal.,

2001

b;Miller

etal.,20

05

Sedimen

tatio

nan

dcoag

ulation

Flocculatio

n

Infrastructure

DAFin

combina

tionwith

coag

ulationor

"occulatio

neffectiveforremov

alof

cyan

obacteria

lmass,alon

gwith

redu

cing

turbidity

,odo

r,with

outchan

ging

cost.

Positiv

ebu

oyan

cy,variabilityin

morph

olog

yan

dde

nsity

,and

nega

tivesurfacecharge

ofcyan

obacteria

lmaterialp

resentsa

challeng

eforsedimen

tatio

nalon

e.Presen

ceof

NOM

requ

iresincreased

coag

ulan

t.DAFcanalso

remov

epo

sitiv

ely

buoy

antpa

thog

ens.

Crossley

and

Valade

,20

06;

Ghe

rnao

utet

al.,20

10;Su

net

al.,20

12;Teixeira

andRo

sa,

2007

Coarse

!ltration

Infrastructure

Short-term

AC!lte

ruseeffectiveif

adeq

uate

surfacearea;N

OM

decreases

adsorptio

n;activ

ated

carbon

more

effectivethan

clay

orsand

alon

e;bio!

lms

substantially

enha

nceef!cacy

Long

-term

useof

commerciallyavailableAC

!lte

rsisexpe

nsivean

dfacesfouling;

combine

dad

sorptio

nan

dba

cterial

degrad

ationformosteffectiveremov

al,

locally

deriv

edcarbon

!be

rsmay

offer

practical

alternative;

totalp

oresize

and

volumeisim

portan

t(m

inim

ummicropo

regreaterthan

0.35

cm3g–

1an

dmesop

ore

greaterthan

0.40

cm3g–

1 )

Bourne

etal.,20

06;de

Albu-

querqu

eet

al.,20

08;Don

ati

etal.,19

94;G

urbu

zan

dCo

dd,

2008

;Hoet

al.,20

07;Hua

nget

al.,20

07a;

Lambe

rtet

al.,

1996

;Lawton

etal.,

1998

;Mulleret

al.,20

09;P

endleton

etal.,

2001

;Wan

get

al.,

2007

;Warhu

rstet

al.,19

97Pressure

driven

!ltration

Infrastructure

Ultra!

ltrationremov

esbiom

ass;NFremov

esdissolvedMCs;integ

ratio

nof

dissolved

gas"otationan

dNFmostprom

isingfor

Energe

tically

costlypu

mping

ofwater;

foulingof

mem

bran

es;variables

ofwater

"ux,p

ressureacross

mem

bran

es,exact

Campina

san

dRo

sa,2010;Ch

owet

al.,

1997

;Gijsbe

rtsen-

Abraha

mse

etal.,2006

;Lee

(Con

tinues)

Persistence of microcystins in drinking water

J. Appl. Toxicol. 2013 Copyright © 2013 John Wiley & Sons, Ltd. wileyonlinelibrary.com/journal/jat

Table2.

Continue

d

Treatm

entop

tions

Stag

eProv

enmeasures

Specialcon

side

ratio

nsRe

levant

citatio

ns

implem

entatio

n;stillin

developm

ent

holdsprom

iseto

elim

inatetrace

concen

trations

!lte

rspeci!catio

ns(surface

prop

ertie

san

dpo

resize)a

ndwater

quality

andWalker,20

06;Teixeira

and

Rosa,200

6a;Teixeira

andRo

sa,

2006b;

Teixeira

and

Rosa,

2005;Zha

nget

al.,20

11Ch

emical

oxidan

tsInfrastructure

Chlorin

ewidelyin

use–requ

irespH

less

than

8with

a1:

12molar

ratio

ofMC-LR

tochlorin

e,with

atleast0.5mgl–1of

free

chlorin

ean

dacontacttim

eof

30minutes;

perm

anga

nate

moreeffectivebu

tless

common

;gravity

fedcanisterswith

haloge

natedbrom

inean

dchlorin

eho

ldprom

iseat

pointof

use

Chlorin

ationreleases

intracellulartoxins;

uncertainchroniceffectsof

sixen

dprod

ucts

iden

ti!ed

;highlyde

pend

ent

upon

water

quality

,NOM

andtype

ofchlorin

eused

;cum

bersom

ead

ditio

nan

dam

ount

ofchlorin

e,am

ount

necessary

forhigh

concen

trations

isim

practical,

complaintsof

poor

tasteof

water

treated

with

chlorin

e=po

orcompliance

Acero

etal.,20

05;Ch

enan

dYe

h,20

05;Co

ulliette

etal.,

2010

;Daly

etal.,

2007

;Hitzfeld

etal.,

2000

;Merel

etal.,20

10;New

combe

and

Nicho

lson

,20

04;Ro

drigue

zet

al.,20

07b

Photocatalyzed

oxidation

Infrastructure

Consistent

degrad

ationacross

concen

trations

andcong

enerswith

titan

ium

dioxide

coup

ledwith

UVde

grad

ation

Dep

ende

nceup

onUVlig

htpresen

tsan

infrastructure

challeng

ein

resource

poor

region

s;integrated

advanced

oxidation

techno

logies

(UVirrad

iatio

nfollowed

byozon

ation)

have

been

appliedto

bloo

ms

andho

ldprom

ise

Band

alaet

al.,2004;Ch

oiet

al.,

2007;C

ornish

etal.,2000;D

ing

etal.,2010;Feitz

etal.,1999;

Jancula

etal.,

2010;Lawton

and

Robe

rtson

,1999;Lawton

etal.,2003;Liu

etal.,2009;Liu

etal.,2003b;

Liu

etal.,2010;

Pelaez

etal.,2009

AC,

activ

ated

carbon

;DAF,dissolvedair"otation;

LR,aminoacidsleucinean

darginine

atpo

sitio

ns2an

d4;

MC,

microcystin;N

F,na

no!ltration;

NOM,n

atural

orga

nicmatter;UV,

ultraviolet.

A. F. Roegner et al.

J. Appl. Toxicol. 2013Copyright © 2013 John Wiley & Sons, Ltd.wileyonlinelibrary.com/journal/jat

MethodsWe evaluated primary studies, reviews and reports for treatmentoptions for MCs in surface waters, potable water sources andtreatment plants. PubMed, Web of Science and comparablesearch engines were used to identify potential studies, usinggeneral search terms such as “MC removal” or “cyanotoxindegradation,” in addition to technology speci!c searches suchas “oxidative processes in MC removal” or “carbon !ltration ofMCs.” Owing to the overwhelming number of publications onpotential treatment options for MCs, we focused on (1) recentadvances in well-established and widely used technologies,and (2) easily implementable alternatives to existing strategiesand technologies already in use, particularly focusing on low-cost options. We excluded laboratory batch studies of technolo-gies not yet widely employed in water treatment.

Treatment options were then organized according to technol-ogy type (e.g., !ltration versus oxidation) and utility along waterinfrastructure (Table 2). Existing treatment options were evalu-ated for ef!cacy in removal and areas for improved options forstrategies for communities limited by resources were identi!ed.In particular, strategies with the potential to address additionalchallenges presented to these communities (such as pathogenload) were discussed. We did not address potential variabilityacross congeners in removal options; once again, the data re-garding MC congener speci!cs is quite limited.

Results and DiscussionSurface water passes from source to reservoir to treatmentfacility to community point-of-source to household point ofuse (tap) (Fig. 2). Some communities may rely directly on thewater source for subsistence use. Most reviews of cyanotoxinremoval have focused on evaluation of traditional treatmentmodalities within water treatment facilities (Westrick et al.,2010). Limited studies have looked at point of use treatmentthat can be implemented readily and easily in communitieswith minimal resources (Pawlowicz et al., 2006; Coullietteet al., 2010).

Removal Strategies

Sedimentation and coagulation/!occulation. The purpose ofsedimentation and coagulation is to remove coarse algaematerial, organic debris and inorganic matter; however, physicalperturbations involved may result in cyanobacterial cell lysis anda direct increase in dissolved toxins. The positive buoyancy(a challenge for sedimentation), the low speci!c density,motility, variable morphologies and negative surface charge oforganic cyanobacterial material complicate a process thatquite effectively removes inorganic particles of a similar size(Ghernaout et al., 2010). Charge neutralization can enhancespherical cell removal but cell morphology varies widely acrosscyanobacterial species and even across strains. Finally, local wa-ter quality (Teixeira and Rosa, 2007) and recurrent use (Sun et al.,2012) in"uences ef!cacy of removal. Dissolved air "otation (DAF)used in combination with coagulation and "occulation appearsto work consistently across morphologies, with an increaseddemand for coagulant in the presence of hydrophobic naturalorganic matter (NOM). DAF reduces turbidity, odor and a widearray of positively buoyant contaminants without remarkablychanging cost of treatment from coagulation and sedimentation

(Crossley and Valade, 2006). The simultaneous ability to removepositively buoyant pathogens such as Cryptosporidium andGiardia from the water source (Betancourt and Rose, 2004) makeDAF suitable for watersheds with ongoing nutrient loading andrecurrent blooms as long as such infrastructure is available and"occulant concentrations used are appropriate for the givenNOM load. Alternatively, gross algae material can be manuallyremoved from surface reservoirs or water intake areas providedappropriate protective equipment is worn and care is taken notto lyse the cells during the removal process.Despite gross removal of algal material and intracellular

toxins, extracellular toxins may persist and pose a substantialpublic health risk with respect to both acute and chronicexposures. Multiple technologies have been explored forremoval, but we will focus on those currently in use for generalwater treatment.

Ozonation and ultraviolet disinfection. Despite the increas-ing use of ozonation (O3) for breakdown of NOM and toxicantremoval in drinking water and waste water facilities, relativelylittle data exist with respect to MCs. Batch experiments demon-strated potential for complete degradation in sterile water. Thepresence of algae material competes for oxidants and thusreduces ef!ciency of toxin degradation (Miao et al., 2010). Ozona-tion in the water treatment chain may result in algae cell lysis andincrease dissolved MCs (Miao et al., 2009). However, UV irradiationfor 5 min with subsequent ozonation at 0.2mg l–1 was suf!cient totreat a toxic surface scum (containing 100 !g l–1 MC-LR) withinWHO recommended guidelines (Liu et al., 2010). A dose of

Figure 2. Strategies for intervention against microcystin contaminationalong the drinking water supply chain from source to end consumer.

Persistence of microcystins in drinking water

J. Appl. Toxicol. 2013 Copyright © 2013 John Wiley & Sons, Ltd. wileyonlinelibrary.com/journal/jat

ozonation at 0.5 mg l–1 was required to degrade the toxins toless than 0.1 !g l–1. More effective than ozonation alone, UValone, concurrent UV irradiation and ozonation (Liu et al.,2010), UV treatment followed by ozonation warrants furtherinvestigation. The cost and technology will be prohibitive inresource challenged regions, but the combination could offeran alternative for existing treatment plants looking for morerigorous removal to prevent low levels in the developed world.UV degradation of MCs alone requires high UV lamp doses,which are orders of magnitude higher than those typically usedin treatment facilities (Westrick et al., 2010).

Activated carbon. By far, as a single technology, activatedcarbon most effectively removes dissolved MCs from a watersource, with reported levels of up to 99% removal. Saturationof !lters over time and the cost of the technology make it anunviable solution for resource-limited communities and evena challenge for implementation in modernized water treat-ment facilities (Westrick et al., 2010). Total pore area andsurface characteristics are critical for ef!cacy of adsorptionof MCs but commercially available !lters vary widely in totalpore surface area and material properties. Larger pore sizesoutperform !ner substrates, but sources of carbons can varyconsiderably in pore size. Mesopores range from 2 to 50 nmin diameter with sizeable surface areas for adsorptions, whilemicropores (< 2 nm) hold fewer adsorption sites and restrictwater "ow, making them less effective at removal. Wood-based AC contains mesopores and micropores, while coconut-based !bers only have micropore-driven smaller total surfaceareas. Entropy-driven adsorption relies on cumulative surface areaso wood generally outperforms coal and coconut-based carbons(Pendleton et al., 2001). Pore size indices insuf!ciently characterizecommercial !lters (Muller et al., 2009) and no internationalstandard is available. Some carbon !lters have removed as littleas 10% of total cyanobacterial biomass with less than 50%removal of toxin (50 !g l–1) (Lawton et al., 1998).

Activated carbon water in home puri!cation !lters used byconsumers in the United States have been shown to effectivelyremove greater than 99.7% of MC-LR in deionized water, buthave not been challenged with increased toxin loads, othercontaminants, NOM or repeated use (Horman et al., 2004). Ona larger scale, two full-scale water treatment plants in Canadaemploying coagulation–sedimentation, dual media !ltration andchlorination in combination with either granular (GAC) orpowder-activated (PAC) carbons removed more than 80% ofnaturally-occurring dissolved MCs (1–10 !g L–1); while attainingWHO guidelines, residual amounts consistently remained from0.1 to 0.5 !g L–1 (Lambert et al., 1996). Concentration of PACnecessary for removal exceeds typical usage in treatmentfacilities (Donati et al., 1994). In addition, the pH and the pHzpc

(zero point of charge) of the substrate substantially in"uenceadsorption to the carbon. The higher the pHzpc of the material,the more likely that the activated carbon will have a neutral orpositive charge under typical water conditions and adsorbMCs or cyanobacterial peptides (Huang et al., 2007b; Hnatukovaet al., 2011). NOM present in the water competes for adsorptionsites and reduces removal. Chlorine pre-treatment of waterresults in a decreased adsorption due to reaction of residualchlorine with active carbon surface sites; this !nding presentsa problem because normal treatment dosages of chlorine donot effectively degrade MCs and chlorine is in widespread use(Huang et al., 2007b).

The growth of microorganisms on these !lter surfaces iscontroversial. Some work has indicated that bio!lm formationenhances ef!cacy through biodegradation in combination withadsorption, even in the presence of NOM, and enhanceslongevity of AC !lters (Huang et al., 2007a). In the removal oftwo MCs (LR and LA) from natural waters by sterile andnon-sterile GAC !lters and sand of similar particle size, thesand !lter failed to remove MCs until bio!lm formationpeaked at 7 months with 100% removal ef!cacy. Initially,the sterile GAC !lter outperformed the non-sterile GAC !lteras bio!lm formation reduces pore size, decreasing potentialadsorption sites. Moreover, after 1 month, the non-sterileGAC achieved 100% ef!cacy, indicating increased microbialactivity. The sterile !lter never exceeded 70% and 40%ef!cacy for LR and LA and faces saturation in long-term use(Wang et al., 2007). However, a more recent study at the lab-oratory pilot scale found that virgin (sterile) GAC was moreeffective at removing MC-LR from 9 to 47 !g l–1 to belowthe WHO provisional guideline, but became less effectiveupon colonization by bacteria, due to competitive bindingof proteins released by bacteria (Drogui et al., 2012). Removalby PAC again required high concentrations (100 mg l–1 PAC)to remove at most 86% of the MC-LR to 3 !g l–1 (still abovethe WHO recommendation), making it a less feasible option.The discrepancy in !ndings with regard to bio!lm formationmay be explained by presence or absence of MC degradingbacteria.

An enzymatic assay (Biolog MT2) has been used to identifynative bacteria species in surface waters (Manage et al., 2010)and could be used to screen for native bio!lm capabilities.Harvested natural river bio!lm from Lake Mead watertreatment facilities facilitated degradation of MCs in tapwater (t1/2 = 14 days) and river water (t1/2 = 8 days), mostnotably when pre-exposed to bloom extract (t1/2 = 44 h and20 h for unexposed and exposed, respectively). Heteroge-neous bacterial cultures taken from Lake Mead waters achievedcomparable degradation rates to commercially availablebio!lters (Eleuterio and Batista, 2010). However, biodegrada-tion pathways in !lters need to be more fully characterizedand may be highly variable dependent upon water conditionsand native species. In addition, the literature varies consider-ably in the time frame for degradation, generally on the orderof days to weeks; in an emergency scenario, this technologyalone will not be suf!cient.

Chlorination and permanganate. Widely used for disinfec-tion, chlorination is already implemented around the worldand well characterized with regard to soluble MC degradation.Unfortunately, it varies widely in actual performance and re-quires concentrations of chlorine much higher than those typi-cally used. In addition to potential for disinfection by-productsand degradation product toxicity, the taste and odor of chlorineadditives can be a problem for household compliance and use.With six breakdown products identi!ed (Daly et al., 2007),degradation rates vary with water quality, competing NOMand toxicants, and chlorine compound used (Hitzfeld et al.,2000; Newcombe and Nicholson, 2004; Acero et al., 2005;Xagoraraki et al., 2006; Merel et al., 2010). While removing mostcyanotoxins under controlled parameters (particularly whenmaintained at pH 5–6 in warmer water temperatures), chlorina-tion generates chlorination by-products with undesirablehealth effects (Merel et al., 2010). Effective chlorination occurs

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at a pH below 8 with a 1: 12 molar ratio of MC-LR to chlorine andnecessitates at least 0.5 mg l–1 of free chlorine and a contacttime of 30 min (Hitzfeld et al., 2000; Newcombe and Nicholson,2004; Merel et al., 2010). In addition, chlorine concentrationscurrently used in disinfection can result in cyanobacterial lysisand toxin release, and reduce ef!cacy of other treatmentmethods as mentioned. Chlorination is frequently the onlytreatment of raw water in limited resource settings, so removalof cells must !rst be achieved, as evidence suggests that intra-cellular release of MC from cells exceeds the rate of oxidationby free chlorine (Daly et al., 2007). Recent evidence suggeststhat the formation of disinfection by-products increases inthe presence of blooms with very high cell counts to levelswell above those considered a health risk (Zamyadi et al.,2012a). A recent study at a drinking water treatment facilityfound that coarse removal followed by !ltration and !nallyby chlorination did not suf!ciently reduce dissolved MCs (2.47mg l–1 remained in chlorinated drinking water) to below theWHO guideline (Zamyadi et al., 2012b). Given all of these stipula-tions, chlorine treatment may be contraindicated, particularly insettings where extracellular toxin concentration cannot be closelymonitored.

Permanganate oxidation exhibits greater ef!cacy at removalMCs and across water quality conditions. Unfavorable discolor-ation of vessels has limited use of potassium permanganate intreatment systems. Yet permanganate also controls taste andodor, removes color from water, controls biological growth,removes metals and enhances coagulation and !ltration pro-cesses. Similar to chlorine, degradation rates of congenersdepended upon initial oxidant concentration and water tempera-ture, yet multiple congener (LR, RR, YR) removal occurred even atacidic pH (Chen and Yeh, 2005; Chen et al., 2005; Rodriguez et al.,2007a, 2007b). Permanganate holds promise for short-termcommunity or household use as an alternative to chlorinationbecause of pH independence and lack of the residual taste ofchlorine. More information must be determined about potentiadisinfection by-products before permanganate can be offered asa replacement for chlorination in these settings.

Nano"ltration and ultra"ltration.Nano!ltration (NF) and ultra!l-tration (UF) involve pressure-driven !ltration through small poresto remove pathogens or contaminants not typically removedthrough physical coarse !ltration. The technology is an emergingarea of focus for water treatment plants to determine if it canbecome cost-effective and implementable. NF (pore size~ 1 nm,< 1000 Da) and UF (103–106 Da) physically !lter MCs through acombination of size exclusion and chemical interactions. Mem-branes require costly pumping of water and face fouling problems.To date, UF appears adequately to remove cyanobacterial biomassif backwashing, cleaning and disinfection occur between runs(Chow et al., 1997; Gijsbertsen-Abrahamse et al., 2006). Operatedunder appropriate pressures and "ows, the technology does notappear to result in cell lysis (Campinas and Rosa, 2010) and canbe effective even under variable water conditions. UF does notremove dissolved MCs, but may be used in combination withPAC to remove MCs at high concentrations (Lee and Walker,2006); PAC alleviates transmembrane pressure and substantiallyimproves dissolved organic carbon and MC removal by 40%(Zhang et al., 2011).

NF recycles water repeatedly through the !lter to retain allunwanted compounds of the initial water permeate into retentate.NF completely removed dissolved toxins even in the presence of

bloom extract up to 10 !g L–1 at a low 10% recovery rate of perme-ate (Gijsbertsen-Abrahamse et al., 2006). Removal was 97% effec-tive for three MC congeners across realistic pH (5–8.5) and waterquality conditions (NOM and electrolyte solutions). However,membrane fouling occurred at concentration of 150 !g l–1

(Teixeira and Rosa, 2005). Interestingly, NOM increased removal(Teixeira and Rosa, 2006b).Integration of dissolved gas "otation (air or CO2/air combina-

tion) before NF resulted in 100% removal below the detection limitof MCs (Teixeira and Rosa, 2006a). If implemented in regions withresources and infrastructure and operated under appropriate pres-sures, "ows and recovery rates, in combination with thoroughbackwashing and cleaning, UF and NF may provide very effectivestrategies for removal of intracellular toxins and dissolved toxinsrespectively, particularly when combined with other availabletechnologies.

Alternative strategies. While it remains questionable whethermultistage treatment at water treatment facilities provides suf!-cient barrier against MC breakthrough into drinking water(Schmidt et al., 2002; Hoeger et al., 2004, 2005; Zamyadi et al.,2012b), it is clear there is no single existing strategy available forpoint of use in outbreak scenarios in regions of the world withlimited resources and infrastructure, apart from seeking analternate water source. Chlorination presents a clear health risk.Even commercially available carbon !lters can fail to removeMCs along with other contaminants and pathogens of concernin compromised water supplies (Horman et al., 2004). We identifyemerging promising alternatives in the hope they will be morerigorously evaluated for point of use.Expensive and not always available commercially in certain

regions, activated carbon can be derived from a wide variety ofsources. Minimal surface area speci!cations for functional AC!lters include a secondary micropore volume greater than0.35 cm3 g–1 and mesopore greater than 0.40 cm3 g–1. Locallyfabricated carbon !lters in Brazil were evaluated as potentialsustainable alternatives to commercially available ones (deAlbuquerque et al., 2008). Pinewood and sugarcane bagasse AC!lters recovered 200 !g MC mg–1 with 98% ef!ciency, surpassingcommercial !lter performance with large mesopores (volume be-tween 0.39 and 1.06 cm3 g–1). Sterile coconut shell and sugar canebagasse outperformed commercial ACs in saturation experimentsin longevity and capacity (de Albuquerque et al., 2008). Low-costAC from the seed husks of a pan-tropical tree, Moringa oleifera(Warhurst et al., 1997), pumice (Gurbuz and Codd, 2008) andpeat (Sathishkumar et al., 2010) demonstrated ef!cient removalin saturation experiments. More recently, a bamboo-basedcharcoal modi!ed with chitosan effectively removed MCs inbatch experiments. Biologically active slow sand !ltrationreduced MCs by approximately 80% over 2 days (Bourne et al.,2006). Finally, loose carbon nanotubes in solution with highlevels of two MCs (mg l–1) outperformed wood-based ACs andclays in adsorption experiments (Yan et al., 2006). While all ofthese coarse !ltration options provide potentially more sustain-able and affordable alternatives to traditional activated carbon,none have been critically evaluated either at point of use orscaled to water treatment facilities, or critically examined forsaturation over time.Titanium dioxide catalyzed UV photo-oxidation effectively

degrades MCs (Lawton and Robertson, 1999; Cornish et al., 2000;Lawton et al., 2003; Liu et al., 2003a) and may represent an areafor future exploration in resource-limited regions. Like activated

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carbon, TiO2 source materials have varied in performance(Liu et al., 2009). Reaction by products do not demonstrateacute toxicity (Liu et al., 2002), but as with chlorination,chronic health exposures remain a concern. It may be possi-ble to catalyze reactions in natural sunlight using naturallyoccurring oxidants. Phthalocyanines (pigments presentnaturally in blooms) enhanced photo-degradation in naturallight to approximately 60% reduction within a 24-h period(Jancula et al., 2010).

Novel gravity-fed household drinking water treatmentsystems with canisters containing halogenated bromine orchlorine media demonstrated ef!cacious removal of MCsand an indicator bacteriophage (Coulliette et al., 2010).Advantageous in avoiding direct chemical additions to watersources and avoiding taste/odor concerns, bromine canistersachieved close to 90% removal of MCs at an initial concen-tration of 2 !g l–1. These contained point-of-source interven-tions are capable of removing pathogens and cyanotoxinsand must be evaluated at higher concentrations and withinhousehold use. Strategies must address the likely simulta-neous presence of fecal pathogens and cyanobacterial toxinsin nutrient-rich blooms (Wilhelm et al., 2010).

As mentioned, one dif!culty in evaluating removal systemsis the detection of MCs. In addition to development ofless expensive enzyme-linked immunosorbent assays (Brenaet al., 2006), detection of "uorescence from pigmentsreleased from cyanobacterial cells has tightly correlated withthe release of MCs (Gijsbertsen-Abrahamse et al., 2006) andcould perhaps be modi!ed as a low-cost screening methodfor ef!cacy of treatment.

Prevention

Prevention of nutrient loading into freshwater ecosystemseliminates the long-term, ecological effects, heavy economicburden placed on regional and local communities (Steffensen,2008; Dodds et al., 2009) and overall health risk. As no singletreatment fully removes MCs from contaminated public watersupplies and multiple strategies can leave trace amounts in tapwater with unknown long-term health consequences (Schmidtet al., 2008; Martinez Hernandez et al., 2009), removal frompotable water sources places an additional economic burden,often an insurmountable one, in resource-limited regions.Detection and clean-up challenge communities regardless ofresources. Sewage diversion and limitation of nonpoint sourcerunoff (particularly, sources of phosphorus and nitrogen) areinstrumental to reducing bloom formation (Smith, 2003;Conley et al., 2009). Effective strategies begin with reductionof fertilizer use and wastewater runoff and placement ofbarriers to nutrient input. These approaches often requirelegislative intervention and community cooperation, in additionto speci!c watershed considerations.

Watershed persistence and removal. The hydrophilic MCspersist in the water column once released largely due to theirstable cyclic peptide structure. Eventual removal occurs throughdilution, pH and temperature degradation, photodegradation,biological degradation, and sorption to sediment or particulatematter (Harada and Tsuji, 1998). Dilution depends on rainfall,basin capacity, surrounding landscape and watershed manage-ment decisions. Drought, water diversion or dam constructionaugment likelihood of blooms; climate change and pulse eventscan exacerbate blooms in particular watersheds (El-Shehawy et al.,

2012; Paerl and Paul, 2012). Increased "ow can facilitate toxindilution in addition to potentially reducing bloom formation.

Compared with other cyanotoxins, MCs are remarkablystable compounds. Identi!ed repeatedly in brackish waters(Mazur-Marzec et al., 2008) and with no effect of salinity upondegradation, MCs withstand several hours of boiling (a primarytreatment method in many regions) and resist chemical hydrolysisor oxidation at neutral pH. The half-life under environmentallyrealistic temperatures and pH approaches 10 weeks, with onlyextremes of temperature and pH substantially shortening thisnontoxic degradation to 3 weeks (Harada et al., 1996).

Irradiation, water column depth and clarity, and bloomcomponents in"uence photodegradation of MCs. Natural or "uo-rescent light alone insuf!ciently degraded MCs (Tsuji et al., 1995)with approximately 90% of MC-LR remaining after 26 days.The presence of water-soluble pigments (phycocyanins) hasaccelerated degradation under natural light with less than 5%remaining after 29 days (Harada and Tsuji, 1998). Preliminary !eldassays suggest that photodegradation can remarkably improveremoval in shallow or well mixed systems as light penetrationplays an important role; photodegradation in the presence ofNOM removed 80% of MCs from the surface layer at full sunlight(Wormer et al., 2010). Enhanced mixing, as well as thin not deeplayers of reservoir water exposed to sunlight, can help expediteremoval. Potentially, water !lms could be run over a titaniumcatalyst while exposed to sunlight. Few studies have looked atthe management and design of reservoirs to facilitatephotodegradation in situ.

Biological degradation by microorganisms within cyano-bacterial mats suggests the importance of maintaining healthybloom conditions and avoiding application of algicides andbiocides. Algicides and biocides not only add toxic agents tothe water but can lyse the cyanobacterial cells resulting inincreased dissolved toxin concentrations and health risk.Bacterial degradation of MCs have been well described (Bourneet al., 1996, 2001; Ho et al., 2007; Manage et al., 2010) and batchreactors with bacteria take up to 6 days to eliminate MCs;however, MC degradation capabilities extend beyond bacteriato other species present within the heterogeneous mats.Rotifers, Daphnia, nano"agellates (Monas sp.) and other aquaticmicroorganisms prey on Microcystis species (Saito et al., 2003).Harvesting these native species may improve bio!lter perfor-mance (Gumbo et al., 2008). Sedimentation and subsequentdegradation also play a substantial role in removal from large,shallow lakes. Sediments collected from Lake Taihu, China,revealed high concentrations of toxin compared from theabove water column (Chen et al., 2008). Isolation ofStenotrophomonas sp. from the sediment revealed completedegradation of MC-LR and MC-RR (0.7 and 1.7 !g ml–1 respec-tively) within 24 h (Chen et al., 2010).

Aquatic plants have demonstrated ef!cient removal of MCsfromwater and soil (Nimptsch et al., 2008). Pond investigations re-vealed potential for 5 g l–1 of biomass of plants to remove MC-LRfrom initial concentrations of 12.1 and 9.2 !g l–1 to below theWHO guideline in less than 3 days. Aquatic plants also enhancesurfaces for bio!lm formation and could be indispensable inmanaging small reservoirs (Carriere et al., 2010; Westrick et al.,2010). For regions with limited resources and infrastructure,the prospect of planting native aquatic species for removal,combined with locally harvested bio!lms, provides a morerealistic approach than point-of-source interventions at thelocal community level.

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J. Appl. Toxicol. 2013Copyright © 2013 John Wiley & Sons, Ltd.wileyonlinelibrary.com/journal/jat

Finally, the natural watershed can !lter cyanobacterial bio-mass and remove or biodegrade extracellular toxins as watermoves from source to point of use. Still largely empirical, !eldsite evaluation of cyanotoxin removal by bank !ltration under-scores the importance of understanding local sediment andmicrobial communities through paired bench top studies;adsorption can be signi!cantly altered by sediment type andmorphology and bacterial community (Lahti et al., 2001b; Dillonet al., 2002); Miller et al., 2005). In addition, higher pH and lowersalinity decrease adsorptive capacity of all sediment. Thus,public health of!cials should monitor rigorously at differenttimes of the year for ef!cacy. Large-scale biologically activeslow sand !ltration for reservoirs may help remove dissolvedMCs (Grutzmacher et al., 2002). These types of interventions atthe watershed can help reduce the burden faced by treatmentfacilities if properly designed.

ConclusionsNo single removal strategy consistently removes MCs acrossconcentrations and water quality conditions. Ef!caciousremoval necessitates a combination of strategies designedwith knowledge of local watershed, infrastructure, resourcesand end use. In economic resource-rich regions of the world,emphasis must be placed on multistage treatment ap-proaches, particularly given potential residual levels in tapwater and concern over chronic health effects. Size of treat-ment facility, water source, local water quality, populationserved, expertise and resources must determine the localapproach. Bioaugmented carbon !lters, dissolved gas "ota-tion followed by NF, and UV irradiation followed by ozona-tion all demonstrate effectiveness in controlled laboratorysettings and offer options for evaluation of ef!cacy in watertreatment plants.

Given the cost and challenge of implementation of large-scaleinfrastructures for potable water treatment in remote anddisadvantaged areas of the world, efforts at the watershed level(bank !ltration, planting of aquatic plants for uptake or physicalbarriers, and harvesting of cyanobacterial mats) combinedwith ingenious designs for point-of-source or point of tapinterventions for dissolved MCs will be indispensable with hopesof future removal technology. Site-speci!c studies looking at ef-!cacy of removal by gross methods (bank !ltration, aquatic plantuptake or wetland !ltration and harvesting of cyanobacterialmats) must be delineated in the future. Increased surveillancefor potential MC-related animal intoxications may improve ourunderstanding of health risk and provide study areas forintervention strategies to reduce risk. MC contamination insurface waters truly represents a global and local challengethat depends on the cooperation and collaboration of theinternational community.

Con!ict of interestThe Authors did not report any con"ict of interest.

Funding SourceThe !rst author was supported by an USEPA STAR GraduateStudent Fellowship through the duration of the preparation ofthe manuscript.

References

Acero JL, Rodriguez E, Meriluoto J. 2005. Kinetics of reactions betweenchlorine and the cyanobacterial toxins microcystins. Water Res. 39(8):1628–1638.

Ahmed S, Raknuzzaman M, Akther H, Ahmed S. 2007. The role ofcyanobacteria blooms in cholera epidemic in Bangladesh. J. Appl.Sci 7(13): 1785–1789.

de Albuquerque EC, Mendez MOA, Coutinho AD, Franco TT. 2008.Removal of cyanobacteria toxins from drinking water by adsorptionon activated carbon !bers. Mat. Res. 11(3): 371–380.

Alonso-Andicoberry C, Garcia-Villada L, Lopez-Rodas V, Costas E. 2002.Catastrophic mortality of "amingos in a Spanish national park causedby cyanobacteria. Vet. Rec. 151(23): 706–707.

Azevedo SM, Carmichael WW, Jochimsen EM, Rinehart KL, Lau S,Shaw GR, Eaglesham GK. 2002. Human intoxication by microcystinsduring renal dialysis treatment in Caruaru-Brazil. Toxicology 181–182:441–446.

Backer LC, Carmichael W, Kirkpatrick B, Williams C, Irvin M, Zhou Y,Johnson TB, Nierenberg K, Hill VR, Kieszak SM, Cheng YS. 2008.Recreational exposure to low concentrations of microcystins duringan algal bloom in a small lake. Mar. Drugs 6(2): 389–406.

Backer LC, McNeel SV, Barber T, Kirkpatrick B, Williams C, Irvin M, Zhou Y,Johnson TB, Nierenberg K, Aubel M, LePrell R, Chapman A, Foss A,Corum S, Hill VR, Kieszak SM, Cheng YS. 2010. Recreational exposureto microcystins during algal blooms in two California lakes. Toxicon55(5): 909–921.

Bandala ER, Martinez D, Martinez E, Dionysiou DD. 2004. Degradation ofmicrocystin-LR toxin by Fenton and Photo-Fenton processes. Toxicon43(7): 829–832.

Bateman KP, Thibault P, Douglas DJ, White RL. 1995. Mass-spectralanalyses of microcystins from toxic cyanobacteria using onlinechromatographic and electrophoretic separations. J. Chromatogr. A712: 253–268.

Bednarczyk D. 2010. Fluorescence-based assays for the assessment ofdrug interaction with the human transporters OATP1B1 andOATP1B3. Anal. Biochem. 405: 50–58.

Benson JM, Hutt JA, Rein K, Boggs SE, Barr EB, Fleming LE. 2005. Thetoxicity of microcystin LR in mice following 7 days of inhalationexposure. Toxicon 45(6): 691–698.

Betancourt WQ, Rose JB. 2004. Drinking water treatment processes forremoval of Cryptosporidium and Giardia. Vet. Parasitol. 126(1–2):219–234.

Billam M, Mukhi S, Tang L, Gao W, Wang JS. 2008. Toxic response indica-tors of microcystin-LR in F344 rats following a single-dose treatment.Toxicon 51(6): 1068–1080.

Blaha L, Marsalek B. 2003. Contamination of drinking water in the CzechRepublic by microcystins. Arch. Hydrobiol. 158(3): 421–429.

Bourne DG, Jones GJ, Blakeley RL, Jones A, Negri AP, Riddles P. 1996.Enzymatic pathway for the bacterial degradation of the cyanobacterialcyclic peptide toxin microcystin LR. Appl. Environ. Microbiol. 62(11):4086–4094.

Bourne DG, Riddles P, Jones GJ, Smith W, Blakeley RL. 2001. Charac-terisation of a gene cluster involved in bacterial degradation ofthe cyanobacterial toxin microcystin LR. Environ. Toxicol. 16(6):523–534.

Bourne DG, Blakeley RL, Riddles P, Jones GJ. 2006. Biodegradation of thecyanobacterial toxin microcystin LR in natural water and biologicallyactive slow sand !lters. Water Res. 40(6): 1294–1302.

Brena BM, Diaz L, Sienra D, Ferrari G, Ferraz N, Hellman U, Gonzalez-Sapienza G, Last JA. 2006. ITREOH building of regional capacity tomonitor recreational water: development of a non-commercialmicrocystin ELISA and its impact on public health policy. Int. J. Occup.Environ. Health 12(4): 377–385.

Burch MD. 2008. Effective doses, guidelines & regulations. Adv. Exp. Med.Biol. 619: 831–853.

Campinas M, Rosa MJ. 2010. Assessing PAC contribution to the NOMfouling control in PAC/UF systems. Water Res. 44(5): 1636–1644.

Carmichael WW, Beasley V, Bunner DL, Eloff JN, Falconer I, Gorham P,Harada K, Krishnamurthy T, Yu MJ, Moore RE, et al. 1988. Naming ofcyclic heptapeptide toxins of cyanobacteria (blue-green algae).Toxicon 26(11): 971–973.

Carriere A, Prevost M, Zamyadi A, Chevalier P, Barbeau B. 2010.Vulnerability of Quebec drinking-water treatment plants to cyanotoxinsin a climate change context. J. Water Health 8(3): 455–465.

Persistence of microcystins in drinking water

J. Appl. Toxicol. 2013 Copyright © 2013 John Wiley & Sons, Ltd. wileyonlinelibrary.com/journal/jat

Chen JJ, Yeh HH. 2005. The mechanisms of potassium permanganate onalgae removal. Water Res. 39(18): 4420–4428.

Chen T, Zhao X, Liu Y, Shi Q, Hua Z, Shen P. 2004. Analysis ofimmunomodulating nitric oxide, iNOS and cytokines mRNA in mousemacrophages induced by microcystin-LR. Toxicology 197: 67–77.

Chen X, Xiao B, Liu J, Fang T, Xu X. 2005. Kinetics of the oxidation ofMCRR by potassium permanganate. Toxicon 45(7): 911–917.

Chen W, Song L, Peng L, Wan N, Zhang X, Gan N. 2008. Reduction inmicrocystin concentrations in large and shallow lakes: water andsediment-interface contributions. Water Res. 42(3): 763–773.

Chen J, Hu LB, Zhou W, Yan SH, Yang JD, Xue YF, Shi ZQ. 2010. Degrada-tion of microcystin-LR and RR by a Stenotrophomonas sp. strain EMSisolated from Lake Taihu, China. Int. J. Mol. Sci. 11(3): 896–911.

Choi H, Antoniou MG, Pelaez M, De la Cruz AA, Shoemaker JA, DionysiouDD. 2007. Mesoporous nitrogen-doped TiO2 for the photocatalyticdestruction of the cyanobacterial toxin microcystin-LR under visiblelight irradiation. Environ. Sci. Technol. 41(21): 7530–7535.

Chorus I, Falconer IR, Salas HJ, Bartram J. 2000. Health risks caused byfreshwater cyanobacteria in recreational waters. J. Toxicol. Environ.Health B Crit. Rev. 3(4): 323–347.

Chow CWK, Panglisch S, House J, Drikas M, Burch MD, Gimbel R. 1997. Astudy of membrane !ltration for the removal of cyanobacterial cells.J. Water Serv. Res. Technol. Aqua 46(6): 324–334.

Codd GA. 2000. Cyanobacterial toxins, the perception of water quality,and the prioritisation of eutrophication control. Ecol. Eng. 16: 51–60.

Conley DJ, Paerl HW, Howarth RW, Boesch DF, Seitzinger SP, Havens KE,Lancelot C, Likens GE. 2009. Ecology. Controlling eutrophication:nitrogen and phosphorus. Science 323(5917): 1014–1015.

Cornish BJPA, Lawton LA, Robertson PKJ. 2000. Hydrogen peroxideenhanced photocatalytic oxidation of microcystin-LR using titaniumdioxide. Appl. Catalysis B Environ. 25: 59–67.

Coulliette AD, Peterson LA, Mosberg JA, Rose JB. 2010. Evaluation of anew disinfection approach: ef!cacy of chlorine and brominehalogenated contact disinfection for reduction of viruses andmicrocystin toxin. Am. J. Trop. Med. Hyg. 82(2): 279–288.

Crossley IA, Valade MT. 2006. A review of the technological developmentsof dissolved air "otation. J Water Supply Res T 55(7–8): 479–491.

de la Cruz AA, Antoniou MG, Hiskia A, Pelaez M, Song W, O’Shea KE,He X, Dionysiou DD. 2011. Can we effectively degrademicrocystins?—Implications on human health. Anti-Cancer AgentsMed. Chem. 11: 19–37.

Daly RI, Ho L, Brookes JD. 2007. Effect of chlorination on Microcystisaeruginosa cell integrity and subsequent microcystin release anddegradation. Environ. Sci. Technol. 41(12): 4447–4453.

Dawson RM. 1998. The toxicology of microcystins. Toxicon 36(7):953–962.

DeVries SE, Galey FD, Namikoshi M, Woo JC. 1993. Clinical and pathologic!ndings of blue-green algae (Microcystis aeruginosa) intoxication in adog. J. Vet. Diagn. Invest. 5(3): 403–408.

Dillenberg HO, Dehnel MK. 1960. Toxic waterbloom in Saskatchewan,1959. Can. Med. Assoc. J. 83: 1151–1154.

Dillon PJ, Miller M, Fallow!eld H, Hutson J. 2002. The potential ofriverbank !ltration for drinking water supplies in relation to microsystinremoval in brackish aquifers. J. Hydrol. 266(3–4): 209–221.

Ding WX, Nam Ong C. 2003. Role of oxidative stress and mitochondrialchanges in cyanobacteria-induced apoptosis and hepatotoxicity.FEMS Microbiol. Lett. 220: 1–7.

Ding WX, Shen HM, Zhu HG, Ong CN. 1998. Studies on oxidative damageinduced by cyanobacteria extract in primary cultured rat hepato-cytes. Environ. Res. 78: 12–18.

Ding J, Shi HL, Timmons T, Adams C. 2010. Release and removal ofmicrocystins from microcystis during oxidative-, physical-, and UV-based disinfection. J. Environ. Eng. Asce 136: 2–11.

Dodds WK, Bouska WW, Eitzmann JL, Pilger TJ, Pitts KL, Riley AJ,Schloesser JT, Thornbrugh DJ. 2009. Eutrophication of U.S. freshwa-ters: analysis of potential economic damages. Environ. Sci. Technol.43: 12–19.

Donati C, Drikas M, Hayes R, Newcombe G. 1994. Microcystin-Lr adsorp-tion by powdered activated carbon. Water Res. 28(8): 1735–1742.

Drogui P, Daghrir R, Simard MC, Sauvageau C, Blais JF. 2012. Removal ofmicrocystin-LR from spiked water using either activated carbon oranthracite as !lter material. Environ. Technol. 33(4–6): 381–391.

Eleuterio L, Batista JR. 2010. Biodegradation studies and sequencing ofmicrocystin-LR degrading bacteria isolated from a drinking waterbio!lter and a fresh water lake. Toxicon 55(8): 1434–1442.

El-Shehawy R, Gorokhova E, Fernandez-Pinas F, del Campo FF. 2012.Global warming and hepatotoxin production by cyanobacteria: whatcan we learn from experiments? Water Res. 46(5): 1420–1429.

Falconer IR. 2008. Health effects associated with controlled exposures tocyanobacterial toxins. Adv. Exp. Med. Biol. 619: 607–612.

Falconer IR, Humpage AR. 2005. Health risk assessment of cyanobacterial(blue-green algal) toxins in drinking water. Int. J. Environ. Res. PublicHealth 2: 43–50.

Fawell JK, James CP, James HA. 1994. Toxins from Blue-Green Algae:Toxicological Assessment of Microcystin-LR and a Method for ItsDetermination in Water. Water Research Centre: Medmenham, UK.

Feitz AJ, Waite TD, Jones GJ, Boyden BH, Orr PT. 1999. Photocatalyticdegradation of the blue green algal toxin microcystin-LR in a naturalorganic-aqueous matrix. Environ. Sci. Technol. 33(2): 243–249.

Feurstein D, Holst K, Fischer A, Dietrich DR. 2009. Oatp-associated uptakeand toxicity of microcystins in primary murine whole brain cells.Toxicol. Appl. Pharmacol. 234(2): 247–255.

Feurstein D, Stemmer K, Kleinteich J, Speicher T, Dietrich DR. 2011.Microcystin congener- and concentration-dependent induction ofmurine neuron apoptosis and neurite degeneration. Toxicol. Sci.124(2): 424–431.

de Figueiredo DR, Azeiteiro UM, Esteves SM, Goncalves FJ, Pereira MJ.2004. Microcystin-producing blooms—a serious global public healthissue. Ecotoxicol. Environ. Saf. 59(2): 151–163.

Fischer WJ, Altheimer S, Cattori V, Meier PJ, Dietrich DR, Hagenbuch B.2005. Organic anion transporting polypeptides expressed in liverand brain mediate uptake of microcystin. Toxicol. Appl. Pharmacol.203(3): 257–263.

Fischer A, Hoeger SJ, Stemmer K, Feurstein DJ, Knobeloch D, Nussler A,Dietrich DR. 2010. The role of organic anion transportingpolypeptides (OATPs/SLCOs) in the toxicity of different microcystincongeners in vitro: a comparison of primary human hepatocytesand OATP-transfected HEK293 cells. Toxicol. Appl. Pharmacol. 245:9–20.

Fleming LE, Rivero C, Burns J, Williams C, Bean JA, Shea KA, Stinn J. 2002.Blue green algal (cyanobacterial) toxins, surface drinking water, andliver cancer in Florida. Harmful Algae 1(2): 157–168.

Francis G. 1878. Poisonous Australian Lake. Nature 18: 11–12.Gehringer MM. 2004. Microcystin-LR and okadaic acid-induced cellular

effects: a dualistic response. FEBS Lett. 557(1–3): 1–8.Ghernaout B, Ghernaout D, Saiba A. 2010. Algae and cyanotoxins

removal by coagulation/"occulation: A review. Desalination WaterTreat. 20(1–3): 133–143.

Giannuzzi L, Sedan D, Echenique R, Andrinolo D. 2011. An acute case ofintoxication with cyanobacteria and cyanotoxins in recreational wa-ter in Salto Grande Dam, Argentina. Mar. Drugs 9(11): 2164–2175.

Gijsbertsen-Abrahamse AJ, Schmidt W, Chorus I, Heijman SGJ. 2006. Re-moval of cyanotoxins by ultra!ltration and nano!ltration. J. Membr.Sci. 276(1–2): 252–259.

Gorchev HG, Ozolins G. 1984. WHO guidelines for drinking-water quality.WHO Chron. 38(3): 104–108.

Grutzmacher G, Bottcher G, Chorus I, Bartel H. 2002. Removal ofmicrocystins by slow sand !ltration. Environ. Toxicol. 17(4): 386–394.

Gumbo RJ, Ross G, Cloete ET. 2008. Biological control ofMicrocystis dominated harmful algal blooms. Afr. J. Biotechnol.7(25): 4765–4773.

Gurbuz F, Codd GA. 2008. Microcystin removal by a naturally-occurringsubstance: pumice. Bull. Environ. Contam. Toxicol. 81(3): 323–327.

Gurbuz F, Metcalf JS, Karahan AG, Codd GA. 2009. Analysis of dissolvedmicrocystins in surface water samples from Kovada Lake, Turkey.Sci. Total Environ. 407(13): 4038–4046.

Guzman RE, Solter PF, Runnegar MT. 2003. Inhibition of nuclear proteinphosphatase activity in mouse hepatocytes by the cyanobacterialtoxin microcystin-LR. Toxicon 41(7): 773–781.

Handeland K, Ostensvik O. 2010. Microcystin poisoning in roe deer(Capreolus capreolus). Toxicon 56(6): 1076–1078.

Harada K, Tsuji K. 1998. Persistence and decomposition of hepatotoxicmicrocystins produced by cyanobacteria in natural environment.J. Toxicol. Toxin Rev. 17(3): 385–403.

Harada K, Tsuji K, Watanabe M, Kondo F. 1996. Stability of microcystinsfrom cyanobacteria-III. Effect of pH and temperature. Phycologia 35(6 Suppl): 83–88.

Heinze R. 1999. Toxicity of the cyanobacterial toxin microcystin-LR torats after 28 days intake with the drinking water. Environ. Toxicol.14: 57–60.

A. F. Roegner et al.

J. Appl. Toxicol. 2013Copyright © 2013 John Wiley & Sons, Ltd.wileyonlinelibrary.com/journal/jat

Hilborn ED, Carmichael WW, Soares RM, Yuan M, Servaites JC, Barton HA,Azevedo SM. 2007. Serologic evaluation of human microcystinexposure. Environ. Toxicol. 22(5): 459–463.

Hitzfeld BC, Hoger SJ, Dietrich DR. 2000. Cyanobacterial toxins: removalduring drinking water treatment, and human risk assessment.Environ. Health Perspect. 108 (Suppl. 1): 113–122.

Hnatukova P, Kopecka I, Pivokonsky M. 2011. Adsorption of cellularpeptides of Microcystis aeruginosa and two herbicides onto activatedcarbon: effect of surface charge and interactions. Water Res. 45(11):3359–3368.

Ho L, Gaudieux AL, Fanok S, Newcombe G, Humpage AR. 2007. Bacterialdegradation of microcystin toxins in drinking water eliminates theirtoxicity. Toxicon 50(3): 438–441.

Hoeger SJ, Shaw G, Hitzfeld BC, Dietrich DR. 2004. Occurrence andelimination of cyanobacterial toxins in two Australian drinking watertreatment plants. Toxicon 43(6): 639–649.

Hoeger SJ, Hitzfeld BC, Dietrich DR. 2005. Occurrence and elimination ofcyanobacterial toxins in drinking water treatment plants. Toxicol.Appl. Pharmacol. 203(3): 231–242.

Hooser SB. 2000. Fulminant hepatocyte apoptosis in vivo followingmicrocystin-LR administration to rats. Toxicol. Pathol. 28(5):726–733.

Hooser SB, Beasley VR, Lovell RA, Carmichael WW, Haschek WM.1989. Toxicity of microcystin LR, a cyclic heptapeptidehepatotoxin from Microcystis aeruginosa, to rats and mice. Vet.Pathol. 26(3): 246–252.

Hooser SB, Beasley VR, Waite LL, Kuhlenschmidt MS, Carmichael WW,Haschek WM. 1991. Actin !lament alterations in rat hepatocytesinduced in vivo and in vitro by microcystin-LR, a hepatotoxinfrom the blue-green alga, Microcystis aeruginosa. Vet. Pathol.28(4): 259–266.

Horman A, Rimhanen-Finne R, Maunula L, von Bonsdorff CH, Rapala J,Lahti K, Hanninen ML. 2004. Evaluation of the puri!cation capacityof nine portable, small-scale water puri!cation devices. Water Sci.Technol. 50: 179–183.

Huang H, Lee N, Young T, Gary A, Lozier JC, Jacangelo JG. 2007a. Naturalorganic matter fouling of low-pressure, hollow-!ber membranes:Effects of NOM source and hydrodynamic conditions. Water Res.41(17): 3823–3832.

Huang WJ, Cheng BL, Cheng YL. 2007b. Adsorption of microcystin-LR bythree types of activated carbon. J. Hazard. Mater. 141: 115–122.

Humbert JF. 2010. Advances in the detection of phycotoxins andcyanotoxins. Anal. Bioanal. Chem. 397(5): 1653–1654.

Ito E, Kondo F, Terao K, Harada K. 1997. Neoplastic nodular formation inmouse liver induced by repeated intraperitoneal injections ofmicrocystin-LR. Toxicon 35(9): 1453–1457.

Ito E, Kondo F, Harada K. 2000. First report on the distribution of orallyadministered microcystin-LR in mouse tissue using an immunostain-ing method. Toxicon 38: 37–48.

Ito E, Kondo F, Harada K. 2001. Intratracheal administration ofmicrocystin-LR, and its distribution. Toxicon 39(2–3): 265–271.

Jancula D, Blahova L, Karaskova M, Marsalek B. 2010. Degradation ofnatural toxins by phthalocyanines—example of cyanobacterial toxin,microcystin. Water Sci. Technol. 62(2): 273–278.

Jayaraj R, Anand T, Rao PV. 2006. Activity and gene expression pro!le ofcertain antioxidant enzymes to microcystin-LR induced oxidativestress in mice. Toxicology 220(2–3): 136–146.

Jayaraj R, Deb U, Bhaskar AS, Prasad GB, Rao PV. 2007. Hepatoprotectiveef!cacy of certain "avonoids against microcystin induced toxicity inmice. Environ. Toxicol. 22(5): 472–479.

Jochimsen EM, Carmichael WW, An JS, Cardo DM, Cookson ST, HolmesCE, Antunes MB, de Melo Filho DA, Lyra TM, Barreto VS, AzevedoSM, Jarvis WR. 1998. Liver failure and death after exposure tomicrocystins at a hemodialysis center in Brazil. N. Engl. J. Med. 338(13): 873–878.

Kalliokoski A, Niemi M. 2009. Impact of OATP transporters on pharmaco-kinetics. Br. J. Pharmacol. 158(3): 693–705.

Kondo F, Matsumoto H, Yamada S, Ishikawa N, Ito E, Nagata S, Ueno Y,Suzuki M, Harada K. 1996. Detection and identi!cation of metabolitesof microcystins formed in vivo in mouse and rat livers. Chem. Res.Toxicol. 9(8): 1355–1359.

Kuiper-Goodman T, Falconer I, Fitzgerald J. 1999. Human health aspects.In: Toxic Cyanobacteria in Water: A Guide to Their Public Health Conse-quences, Monitoring and Management, Chorus IBJ, (ed). E & FN Spon:London; 113–153.

Lahti K, Rapala J, Kivimaki AL, Kukkonen J, Niemela M, Sivonen K.2001a. Occurrence of microcystins in raw water sources andtreated drinking water of Finnish waterworks. Water Sci. Technol.43(12): 225–228.

Lahti K, Rapala J, Kivimaki AL, Kukkonen J, Niemela M, Sivonen K. 2001b.Occurrence of microcystins in raw water sources and treated drinkingwater of Finnish waterworks. Water Sci. Technol. 43(12): 225–228.

Lambert TW, Holmes CFB, Hrudey SE. 1996. Adsorption of microcystin-LRby activated carbon and removal in full scale water treatment. WaterRes. 30(6): 1411–1422.

Lawton LA, Robertson PKJ. 1999. Physico-chemical treatment methodsfor the removal of microcystins (cyanobacterial hepatotoxins) frompotable waters. Chem. Soc. Rev. 28(4): 217–224.

Lawton LA, Cornish BJPA, Macdonald AWR. 1998. Removal ofcyanobacterial toxins (microcystins) and cyanobacterial cells fromdrinking water using domestic water !lters.Water Res. 32(3): 633–638.

Lawton LA, Robertson PKJ, Cornish BJPA, Marr IL, Jaspars M. 2003.Processes in"uencing surface interaction and photocatalytic destruc-tion of microcystins on titanium dioxide photocatalysts. J. Catal. 213:109–113.

Lee J, Walker HW. 2006. Effect of process variables and natural organicmatter on removal of microcystin-LR by PAC-UF. Environ. Sci. Technol.40(23): 7336–7342.

Li Y, Chen JA, Zhao Q, Pu C, Qiu Z, Zhang R, Shu W. 2011. A cross-sectional investigation of chronic exposure to microcystin in relation-ship to childhood liver damage in the Three Gorges Reservoir Region,China. Environ. Health Perspect. 119(10): 1483–1488.

Liu Y, Song L, Li X, Liu T. 2002. The toxic effects of microcystin-LR onembryo-larval and juvenile development of loach, Misgurunsmizolepis Gunthe. Toxicon 40(4): 395–399.

Liu I, Lawton LA, Robertson PKJ. 2003a. Mechanistic studies of thephotocatalytic oxidation of microcystin-LR: An investigation ofbyproducts of the decomposition process. Environ. Sci. Technol.37(14): 3214–3219.

Liu I, Lawton LA, Robertson PK. 2003b. Mechanistic studies of thephotocatalytic oxidation of microcystin-LR: an investigation ofbyproducts of the decomposition process. Environ. Sci. Technol.37(14): 3214–3219.

Liu I, Lawton LA, Bahnemann DW, Liu L, Proft B, Robertson PKJ. 2009. Thephotocatalytic decomposition of microcystin-LR using selectedtitanium dioxide materials. Chemosphere 76(4): 549–553.

Liu X, Chen Z, Zhou N, Shen J, Ye M. 2010. Degradation and detoxi!ca-tion of microcystin-LR in drinking water by sequential use of UVand ozone. J. Environ. Sci. (China) 22(12): 1897–1902.

Lopez-Rodas V, Maneiro E, Lanzarot MP, Perdigones N, Costas E. 2008.Mass wildlife mortality due to cyanobacteria in the Donana NationalPark, Spain. Vet. Rec. 162(10): 317–318.

Lurling M, Faassen EJ. 2013. Dog poisonings associated with a Microcystisaeruginosa bloom in the Netherlands. Toxins 5(3): 556–567.

Manage PM, Edwards C, Lawton L. 2010. Bacterial degradation ofmicrocystin. In Interdisciplinary Studies on Environmental Chemistry— Biological Responses to Contaminants, Hamamura N, Suzuki S,Mendo S, Barroso CM, Iwata H, Tanabe, S (eds). TERRAPUB: Tokyo;97–104.

Martinez Hernandez J, Lopez-Rodas V, Costas E. 2009. Microcystins fromtap water could be a risk factor for liver and colorectal cancer: a riskintensi!ed by global change. Med. Hypotheses 72(5): 539–540.

Maruyama T, Kato K, Yokoyama A, Tanaka T, Hiraishi A, Park HD. 2003.Dynamics of microcystin-degrading bacteria in mucilage ofMicrocystis. Microb. Ecol. 46(2): 279–288.

Matsunaga H, Harada KI, Senma M, Ito Y, Yasuda N, Ushida S, Kimura Y.1999. Possible cause of unnatural mass death of wild birds in a pondin Nishinomiya, Japan: sudden appearance of toxic cyanobacteria.Nat. Toxins 7(2): 81–84.

Mazur H, Pliñski M. 2001. Stability of cyanotoxins, microcystin-LR,microcystin-RR and nodularin in seawater and BG-11 medium ofdifferent salinity. Oceanologia 43(3): 329–339.

Mazur-Marzec H, Spoof L, Kobos J, Pli"ski M, Meriluoto J. 2008.Cyanobacterial hepatotoxins, microcystins and nodularins, in freshand brackish waters of the Pomeranian Province, northern Poland.Oceanol. Hydrobiol. Stud. 37(4): 3–21.

McElhiney J, Lawton LA. 2005. Detection of the cyanobacterialhepatotoxins microcystins. Toxicol. Appl. Pharmacol. 203(3): 219–230.

Merel S, Clement M, Thomas O. 2010. State of the art on cyanotoxins inwater and their behaviour towards chlorine. Toxicon 55(4): 677–691.

Persistence of microcystins in drinking water

J. Appl. Toxicol. 2013 Copyright © 2013 John Wiley & Sons, Ltd. wileyonlinelibrary.com/journal/jat

van der Merwe D, Sebbag L, Nietfeld JC, Aubel MT, Foss A, Carney E.2012. Investigation of a Microcystis aeruginosa cyanobacterialfreshwater harmful algal bloom associated with acute microcystintoxicosis in a dog. J. Vet. Diagn. Invest. 24(4): 679–687.

Miao HF, Lu X, Yan Q, Xie LJ, Ruan WQ. 2009. Degradation of microcystin-lR by ozonation process. Huan Jing Ke Xue 30(11): 3288–3292.

Miao HF, Qin F, Tao GJ, Tao WY, Ruan WQ. 2010. Detoxi!cation anddegradation of microcystin-LR and -RR by ozonation. Chemosphere79(4): 355–361.

Miller MJ, Hutson J, Fallow!eld HJ. 2005. The adsorption ofcyanobacterial hepatoxins as a function of soil properties. J. WaterHealth 3(4): 339–347.

Miller MA, Kudela RM, Mekebri A, Crane D, Oates SC, Tinker MT, StaedlerM, Miller WA, Toy-Choutka S, Dominik C, Hardin D, Langlois G, MurrayM, Ward K, Jessup DA. 2010. Evidence for a novel marine harmfulalgal bloom: cyanotoxin (microcystin) transfer from land to sea otters.PLoS One 5(9): e12576.

Milutinovic A, Sedmak B, Horvat-Znidarsic I, Suput D. 2002. Renal injuriesinduced by chronic intoxication with microcystins. Cell. Mol. Biol. Lett.7: 139–141.

Milutinovic A, Zivin M, Zorc-Pleskovic R, Sedmak B, Suput D. 2003.Nephrotoxic effects of chronic administration of microcystins -LRand -YR. Toxicon 42(3): 281–288.

Milutinovic A, Zorc-Pleskovic R, Petrovic D, Zorc M, Suput D. 2006.Microcystin-LR induces alterations in heart muscle. Folia Biol. (Praha)52(4): 116–118.

Monks NR, Liu S, Xu Y, Yu H, Bendelow AS, Moscow JA. 2007. Potentcytotoxicity of the phosphatase inhibitor microcystin LR andmicrocystin analogues in OATP1B1- and OATP1B3-expressing HeLacells. Mol. Cancer Ther. 6(2): 587–598.

Msagati TA, Siame BA, Shushu DD. 2006. Evaluation of methods for theisolation, detection and quanti!cation of cyanobacterialhepatotoxins. Aquat. Toxicol. 78(4): 382–397.

Muller CC, Raya-Rodriguez MT, Cybis LF. 2009. Powdered activatedcarbon adsorption for microcystin removal from public water supply.Eng. Sanit Ambiental 14: 29–38.

Nasri H, El Herry S, Bouaicha N. 2008. First reported case of turtle deathsduring a toxic Microcystis spp. bloom in Lake Oubeira, Algeria.Ecotoxicol. Environ. Saf. 71(2): 535–544.

Newcombe G, Nicholson B. 2004. Water treatment options for dissolvedcyanotoxins. J. Water Supply Res. Technol. Aqua 53(4): 227–239.

Newcombe G, Chorus I, Falconer I, Lin TF. 2012. Cyanobacteria: impactsof climate change on occurrence, toxicity and water quality manage-ment. Water Res. 46(5): 1347–1348.

Nimptsch J, Wiegand C, P"ugmacher S. 2008. Cyanobacterial toxinelimination via bioaccumulation of MC-LR in aquatic macrophytes: anapplication of the "green liver concept". Environ. Sci. Technol. 42(22):8552–8557.

Oberholster PJ, Myburgh JG, Govender D, Bengis R, Botha AM. 2009.Identi!cation of toxigenic Microcystis strains after incidents of wildanimal mortalities in the Kruger National Park, South Africa.Ecotoxicol. Environ. Saf. 72(4): 1177–1182.

Paerl HW, Paul VJ. 2012. Climate change: links to global expansion ofharmful cyanobacteria. Water Res. 46(5): 1349–1363.

Pawlowicz MB, Evans JE, Johnson DR, Brooks RG. 2006. A study of theef!cacy of various home !ltration substrates in the removal ofmicrocystin-LR from drinking water. J. Water Health 4: 99–107.

Pearson LA, Neilan BA. 2008. The molecular genetics of cyanobacterialtoxicity as a basis for monitoring water quality and public health risk.Curr. Opin. Biotechnol. 19(3): 281–288.

Pelaez M, de la Cruz AA, Stathatos E, Falaras P, Dionysiou DD. 2009.Visible light-activated N-F-codoped TiO2 nanoparticles for thephotocatalytic degradation of microcystin-LR in water. Catal. Today144(1–2): 19–25.

Pendleton P, Schumann R, Wong SH. 2001. Microcystin-LR adsorption byactivated carbon. J. Colloid Interface Sci. 240: 1–8.

P"ugmacher S, Wiegand C, Oberemm A, Beattie KA, Krause E, Codd GA,Steinberg CE. 1998. Identi!cation of an enzymatically formedglutathione conjugate of the cyanobacterial hepatotoxinmicrocystin-LR: the !rst step of detoxication. Biochim. Biophys. Acta1425(3): 527–533.

Pouria S, de Andrade A, Barbosa J, Cavalcanti RL, Barreto VT, Ward CJ,Preiser W, Poon GK, Neild GH, Codd GA. 1998. Fatal microcystin intox-ication in haemodialysis unit in Caruaru, Brazil. Lancet 352(9121): 21–26.

Puschner B, Galey FD, Johnson B, Dickie CW, Vondy M, Francis T,Holstege DM. 1998. Blue-green algae toxicosis in cattle. J. Am. Vet.Med. Assoc. 213(11): 1605–1607, 1571.

Rinehart KL, Namikoshi M, Choi BW. 1994. Structure and biosynthesis oftoxins from blue-green-algae (Cyanobacteria). J. Appl. Phycol. 6(2):159–176.

Robinson NA, Pace JG, Matson CF, Miura GA, Lawrence WB. 1991. Tissuedistribution, excretion and hepatic biotransformation of microcystin-LR in mice. J. Pharmacol. Exp. Ther. 256: 176–182.

Rodriguez E, Majado ME, Meriluoto J, Acero JL. 2007a. Oxidation ofmicrocystins by permanganate: Reaction kinetics and implicationsfor water treatment. Water Res. 41: 102–110.

Rodriguez E, Sordo A, Metcalf JS, Acero JL. 2007b. Kinetics of theoxidation of cylindrospermopsin and anatoxin-a with chlo-rine, monochloramine and permanganate. Water Res. 41(9):2048–2056.

Runnegar MT, Gerdes RG, Falconer IR. 1991. The uptake of thecyanobacterial hepatotoxin microcystin by isolated rat hepatocytes.Toxicon 29: 43–51.

Runnegar M, Berndt N, Kong SM, Lee EY, Zhang L. 1995. In vivo andin vitro binding of microcystin to protein phosphatases 1 and 2A.Biochem. Biophys. Res. Commun. 216: 162–169.

Saito T, Sugiura N, Itayama T, Inamori Y, Matsumura M. 2003. Biodegrada-tion of microcystis and microcystins by indigenous nano"agellateson bio!lm in a practical treatment facility. Environ. Technol. 24(2):143–151.

Sathishkumar M, Pavagadhi S, Vijayaraghavan K, Balasubramanian R,Ong SL. 2010. Experimental studies on removal of microcystin-LRby peat. J. Hazard. Mater. 184(1–3): 417–424.

Schmidt W, Willmitzer H, Bornmann K, Pietsch J. 2002. Production ofdrinking water from raw water containing cyanobacteria—pilot plantstudies for assessing the risk of microcystin breakthrough. Environ.Toxicol. 17(4): 375–385.

Schmidt W, Bornmann K, Imhof L, Mankiewicz J, Izydorczyk K. 2008.Assessing drinking water treatment systems for safety againstcyanotoxin breakthrough using maximum tolerable values. Environ.Toxicol. 23(3): 337–345.

Seithel A, Eberl S, Singer K, Auge D, Heinkele G, Wolf NB, Dorje F, FrommMF, Konig J. 2007. The in"uence of macrolide antibiotics on theuptake of organic anions and drugs mediated by OATP1B1 andOATP1B3. Drug Metab. Dispos. 35(5): 779–786.

Shimizu K, Maseda H, Okano K, Itayama T, Kawauchi Y, Chen R, Utsumi M,Zhang Z, Sugiura N. 2011. How-microcystin degrading bacteriaexpress microcystin degradation activity. Lakes Reservoirs Res.Manage. 16(3): 169–178.

Sivonen K. 1996. Cyanobacterial toxins and toxin production. Phycologia35(6S): 12–24.

Sivonen K. 2008. Emerging high throughput analyses ofcyanobacterial toxins and toxic cyanobacteria. Adv. Exp.Med. Biol. 619: 539–557.

Smith VH. 2003. Eutrophication of freshwater and coastal marine ecosys-tems: a global problem. Environ. Sci. Pollut. Res. Int. 10(2): 126–139.

Steffensen DA. 2008. Economic cost of cyanobacterial blooms. Adv. Exp.Med. Biol. 619: 855–865.

Stewart I, Seawright AA, Shaw GR. 2008a. Cyanobacterial poisoning inlivestock, wild mammals and birds—an overview. Adv. Exp. Med. Biol.619: 613–637.

Stewart I, Seawright AA, Shaw GR. 2008b. Cyanobacterial poisoning inlivestock, wild mammals and birds—an overview. Adv. Exp. Med. Biol.619: 613–637.

Stotts RR, Twardock AR, Haschek WM, Choi BW, Rinehart KL, Beasley VR.1997a. Distribution of tritiated dihydromicrocystin in swine. Toxicon35(6): 937–953.

Stotts RR, Twardock AR, Koritz GD, Haschek WM, Manuel RK, Hollis WB,Beasley VR. 1997b. Toxicokinetics of tritiated dihydromicrocystin-LRin swine. Toxicon 35(3): 455–465.

Sun F, Pei HY, Hu WR, Ma CX. 2012. The lysis of Microcystis aeruginosa inAlCl3 coagulation and sedimentation processes. Chem. Eng. J. 193:196–202.

Suput D, Zorc-Pleskovic R, Petrovic D, Milutinovic A. 2010. Cardiotoxicinjury caused by chronic administration of microcystin-YR. Folia Biol.(Praha) 56: 14–18.

Svircev Z, Krstic S, Miladinov-Mikov M, Baltic V, Vidovic M. 2009. Freshwa-ter cyanobacterial blooms and primary liver cancer epidemiologicalstudies in Serbia. J. Environ. Sci. Health C 27: 36–55.

A. F. Roegner et al.

J. Appl. Toxicol. 2013Copyright © 2013 John Wiley & Sons, Ltd.wileyonlinelibrary.com/journal/jat

Teixeira MR, Rosa MJ. 2005. Microcystins removal by nano!ltrationmembranes. Sep. Purif. Technol. 46(3): 192–201.

Teixeira MR, Rosa MJ. 2006a. Integration of dissolved gas "otation andnano!ltration for M. aeruginosa and associated microcystins removal.Water Res. 40(19): 3612–3620.

Teixeira MR, Rosa MJ. 2006b. Neurotoxic and hepatotoxic cyanotoxinsremoval by nano!ltration. Water Res. 40(15): 2837–2846.

Teixeira MR, Rosa MJ. 2007. Comparing dissolved air "otation andconventional sedimentation to remove cyanobacterial cells ofMicrocystis aeruginosa Part II. The effect of water backgroundorganics. Sep. Purif. Technol. 53: 126–134.

Trinchet I, Cadel-Six S, Djediat C, Marie B, Bernard C, Puiseux-Dao S,Krys S, Edery M. 2013. Toxicity of harmful cyanobacterial bloomsto bream and roach. Toxicon 71: 121–127.

Tsuji K, Watanuki T, Kondo F, Watanabe MF, Suzuki S, Nakazawa H,Suzuki M, Uchida H, Harada KI. 1995. Stability of microcystins fromcyanobacteria—II. Effect of UV light on decomposition and isomer-ization. Toxicon 33(12): 1619–1631.

Turner PC, Gammie AJ, Hollinrake K, Codd GA. 1990. Pneumonia associatedwith contact with cyanobacteria. BMJ 300(6737): 1440–1441.

Van Halderen A, Harding WR, Wessels JC, Schneider DJ, Heine EW,Van der Merwe J, Fourie JM. 1995. Cyanobacterial (blue-greenalgae) poisoning of livestock in the western Cape Province ofSouth Africa. J. S. Afr. Vet. Assoc. 66(4): 260–264.

Vesterkvist PS, Misiorek JO, Spoof LE, Toivola DM, Meriluoto JA. 2012.Comparative cellular toxicity of hydrophilic and hydrophobicmicrocystins on Caco-2 cells. Toxins 4(11): 1008–1023.

Wang H, Ho L, Lewis DM, Brookes JD, Newcombe G. 2007. Discriminatingand assessing adsorption and biodegradation removal mechanismsduring granular activated carbon !ltration of microcystin toxins.Water Res. 41(18): 4262–4270.

Wang Q, Xie P, Chen J, Liang G. 2008. Distribution of microcystins invarious organs (heart, liver, intestine, gonad, brain, kidney and lung)of Wistar rat via intravenous injection. Toxicon 52(6): 721–727.

Warhurst AM, Raggett SL, McConnachie GL, Pollard SJ, Chipofya V,Codd GA. 1997. Adsorption of the cyanobacterial hepatotoxinmicrocystin-LR by a low-cost activated carbon from the seed husksof the pan-tropical tree, Moringa oleifera. Sci. Total Environ. 207(2–3):207–211.

Welker M, Steinberg C. 2000. Rates of humic substance photosensitizeddegradation of microcystin-LR in natural waters. Environ. Sci. Technol.34(16): 3415–3419.

Westrick JA, Szlag DC, Southwell BJ, Sinclair J. 2010. A review ofcyanobacteria and cyanotoxins removal/inactivation in drinkingwater treatment. Anal. Bioanal. Chem. 397(5): 1705–1714.

Wilhelm SW, Farnsley SE, LeCleir GR, Layton AC, Satchwell M,DeBruyn JM, Boyer C, Zhu GW, Paerl H. 2010. The relationshipsbetween nutrients, cyanobacterial toxins and the microbialcommunity in Taihu (Lake Tai), China. Harmful Algae 10(2):207–215.

Wood SA, Heath MW, Holland PT, Munday R, McGregor GB, Ryan KG.2010. Identi!cation of a benthic microcystin-producing !lamentouscyanobacterium (Oscillatoriales) associated with a dog poisoning inNew Zealand. Toxicon 55(4): 897–903.

Wood SA, Holland PT, MacKenzie L. 2011. Development of solid phaseadsorption toxin tracking (SPATT) for monitoring anatoxin-a andhomoanatoxin-a in river water. Chemosphere 82(6): 888–894.

Wormer L, Huerta-Fontela M, Cires S, Carrasco D, Quesada A. 2010.Natural photodegradation of the cyanobacterial toxins microcystinand cylindrospermopsin. Environ. Sci. Technol. 44(8): 3002–3007.

Xagoraraki I, Harrington GW, Zulliger K, Zeier B, Krick W, Karner DA,Standridge JH, Westrick J. 2006. Inactivation kinetics of thecyanobacterial toxin microcystin-LR by free chlorine. J. Environ. Eng.Asce 132(7): 818–823.

Xiong Q, Xie P, Li H, Hao L, Li G, Qiu T, Liu Y. 2009. Involvement of Fas/FasL system in apoptotic signaling in testicular germ cells of maleWistar rats injected i.v. with microcystins. Toxicon 54: 1–7.

Yan H, Gong A, He H, Zhou J, Wei Y, Lv L. 2006. Adsorption ofmicrocystins by carbon nanotubes. Chemosphere 62: 142–148.

Yu S, Zhao N, Zi X. 2001. The relationship between cyanotoxin(microcystin, MC) in pond-ditch water and primary liver cancer inChina. Zhonghua Zhong Liu Za Zhi 23(2): 96–99.

Zamyadi A, Ho L, Newcombe G, Bustamante H, Prevost M. 2012a. Fate oftoxic cyanobacterial cells and disinfection by-products formationafter chlorination. Water Res. 46(5): 1524–1535.

Zamyadi A, MacLeod SL, Fan Y, McQuaid N, Dorner S, Sauve S, Prevost M.2012b. Toxic cyanobacterial breakthrough and accumulation in adrinking water plant: a monitoring and treatment challenge. WaterRes. 46(5): 1511–1523.

Zegura B, Sedmak B, Filipic M. 2003. Microcystin-LR induces oxidativeDNA damage in human hepatoma cell line HepG2. Toxicon 41:41–48.

Zegura B, Zajc I, Lah TT, Filipic M. 2008. Patterns of microcystin-LRinduced alteration of the expression of genes involved in responseto DNA damage and apoptosis. Toxicon 51(4): 615–623.

Zhang Y, Tian J, Nan J, Gao S, Liang H, Wang M, Li G. 2011. Effect of PACaddition on immersed ultra!ltration for the treatment of algal-richwater. J. Hazard. Mater. 186(2–3): 1415–1424.

Zhou L, Yu H, Chen K. 2002. Relationship between microcystin in drinkingwater and colorectal cancer. Biomed. Environ. Sci. 15(2): 166–171.

Persistence of microcystins in drinking water

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