ARTICLE IN PRESS

Environmental Research ] (]]]]) ]]]–]]]

Contents lists available at ScienceDirect

Environmental Research

0013-93

doi:10.1

$Fun

Academ$$Co

of the Un Corr

E-m

Pleasexpo

journal homepage: www.elsevier.com/locate/envres

Cadmium, mercury, and lead in kidney cortex of living kidney donors:Impact of different exposure sources,$,$$

Lars Barregard a,n, Elisabeth Fabricius-Lagging b, Thomas Lundh c, Johan Molne d, Maria Wallin a,Michael Olausson e, Cecilia Modigh a, Gerd Sallsten a

a Department of Occupational and Environmental Medicine, Sahlgrenska University Hospital and University of Gothenburg, P.O. Box 414, SE 405 30 Gothenburg, Swedenb Department of Nephrology, Sahlgrenska University Hospital and Boras Hospital, Swedenc Department of Occupational and Environmental Medicine, Lund University Hospital and Lund University, Swedend Department of Clinical Pathology, Sahlgrenska University Hospital and University of Gothenburg, Swedene Department of Transplantation and Liver Surgery, Sahlgrenska University Hospital and University of Gothenburg, Sweden

a r t i c l e i n f o

Article history:

Received 3 July 2009

Received in revised form

9 October 2009

Accepted 22 October 2009

Keywords:

Cadmium

Mercury

Lead

Kidney

Donor

51/$ - see front matter & 2009 Elsevier Inc. A

016/j.envres.2009.10.010

ding was obtained from Sahlgrenska Univers

y, University of Gothenburg.

mpeting interests: None. The study was appro

niversity of Gothenburg.

esponding author. Fax: +46 31 40 97 28.

ail address: lars.barregard@amm.gu.se (L. Bar

e cite this article as: Barregard, L., etsure sources,. Environ. Res. (2009), d

a b s t r a c t

Background: Most current knowledge on kidney concentrations of nephrotoxic metals like cadmium

(Cd), mercury (Hg), or lead (Pb) comes from autopsy studies. Assessment of metal concentrations in

kidney biopsies from living subjects can be combined with information about exposure sources like

smoking, diet, and occupation supplied by the biopsied subjects themselves.

Objectives: To determine kidney concentrations of Cd, Hg, and Pb in living kidney donors, and assess

associations with common exposure sources and background factors.

Methods: Metal concentrations were determined in 109 living kidney donors aged 24–70 years (median

51), using inductively coupled plasma-mass spectrometry (Cd and Pb) and cold vapor atomic

fluorescence spectrometry (Hg). Smoking habits, occupation, dental amalgam, fish consumption, and

iron stores were evaluated.

Results: The median kidney concentrations were 12.9 mg/g (wet weight) for cadmium, 0.21 mg/g for

mercury, and 0.08 mg/g for lead. Kidney Cd increased by 3.9 mg/g for a 10 year increase in age, and by

3.7 mg/g for an extra 10 pack-years of smoking. Levels in non-smokers were similar to those found in

the 1970s. Low iron stores (low serum ferritin) in women increased kidney Cd by 4.5 mg/g. Kidney Hg

increased by 6% for every additional amalgam surface, but was not associated with fish consumption.

Lead was unaffected by the background factors surveyed.

Conclusions: In Sweden, kidney Cd levels have decreased due to less smoking, while the impact of diet

seems unchanged. Dental amalgam is the main determinant of kidney Hg. Kidney Pb levels are very low

due to decreased exposure.

& 2009 Elsevier Inc. All rights reserved.

1. Introduction

Cadmium, mercury, and lead are all nephrotoxic metals(WHO, 1991, 1992, 1995). Clinical kidney damage has beendemonstrated mainly in connection with occupational exposure(Jarup et al., 1998; Kazantzis et al., 1962). However, in the pastcouple of decades, exposure to levels of cadmium, mercury, andlead at levels found in the general population has been shown toresult in subtle effects on the kidney, for example on renal tubularmarkers and bone (Akesson et al., 2005; Alfven et al. 2000, 2002;

ll rights reserved.

ity Hospital and Sahlgrenska

ved by the Ethics Committee

regard).

al., Cadmium, mercury, andoi:10.1016/j.envres.2009.1

Buchet et al., 1990; De Burbure et al., 2006; Ekong et al., 2006;Ellingsen et al., 2000; Ezaki et al., 2003; Gallagher et al., 2008;Jarup et al., 2000; Jarup, 2002; Osman et al., 1999; Schutte et al.,2008; Staessen et al. 1994, 1999; Thomas et al., 2009; Wu et al.,2001).

Most of the current knowledge on concentrations of heavymetals in the kidneys was obtained in autopsy studies (Bahe-mann-Hoffmeister et al., 1988; Drasch et al., 1992, 1996; Elinderet al., 1976; Falnoga et al., 2000; Friis et al., 1998; Gerhardsson etal., 1986, 1995; Honda and Nogawa, 1987; Johansen et al., 2006,2007; Koizumi et al., 2008; Lyon et al., 1999; Orlowski et al., 1998;Satarug et al., 2002; Torra et al., 1995; Vahter, 1982).

In contrast to autopsy sample studies, assessment of heavymetal concentrations in kidney biopsies from living subjects canbe combined with information about exposure sources likesmoking, diet, and occupation supplied by the biopsied subjectsthemselves (Angerer et al., 1988; Barregard et al., 1999). In

lead in kidney cortex of living kidney donors: Impact of different0.010

ARTICLE IN PRESS

L. Barregard et al. / Environmental Research ] (]]]]) ]]]–]]]2

addition, data can be collected to investigate the relationsbetween kidney metal concentrations and the concentrations insurrogate markers like urine or blood. Moreover, levels of heavymetals in the kidneys can be directly compared with histopatho-logical findings and markers of effects on kidney or bone.

This report presents the first results on levels of Cd, Hg, and Pbin kidney cortex, and the associations with exposure sources, in aproject focused on heavy metals in living Swedish kidney donors.Future findings on kidney function and levels of heavy metals inbiological fluids will be presented elsewhere.

2. Subjects and methods

2.1. Kidney donors

Between January 1999 and June 2002, and between April 2004 and February

2005, 167 donors were invited to take part in the study. A total of 188

transplantations with living kidney donors were performed at the Department

of Transplantation and Liver Surgery at Sahlgrenska University Hospital during

these two periods. Twenty-one donors were not eligible (recipient a child, donor

living abroad, donor not able to take part in study protocol) and were

subsequently not approached. Fifteen donors did not want to participate, so after

informed consent, 152 (81%) subjects were included in the study. Kidney donor

age and sex are presented in Table 1. The study was approved by the Ethics

Committee of the University of Gothenburg.

All potential kidney donors were evaluated according to a standard protocol,

including assessment of kidney function. When accepted, the donor was admitted

1–2 days before the transplantation. Additional evaluation and blood and urine

tests according to the study protocol were made during this period, and the

subjects were again interviewed about medical history and medications.

2.2. Kidney biopsies

As part of the routine procedure during transplantation, a surgical wedge

biopsy (baseline biopsy) from the lower pole of the kidney was obtained after

revascularization in 126 out of 152 subjects (83%). This biopsy was used for

histopathological examination. Most biopsies were representative of renal cortical

Table 1Background factors in 152 living kidney donors.

AllN=152

Age: median (range) 50 (24–70)

Smoking (N)a

Never 60

Ever 91

Active 36

Former 55

Occupationala exposure (N)

Yesb 18

No 133

Diet (N)a

Mixed 148

Vegetarian 3

Fish meals (N)a

o1/month 21

1/monthoNo1/week 59

1/week 41

41/week 30

Amalgam fillingsc

Yes 140

No 7

Weight in kgd: median (range) 74 (49–111)

Kidney weight in ge: median (range) 327 (248–423)

a Information missing for one donor.b Definitive or probable exposure.c Information missing for five donors.d Information missing for three donors.e Estimated (see methods section); missing for three donors.

Please cite this article as: Barregard, L., et al., Cadmium, mercury, andexposure sources,. Environ. Res. (2009), doi:10.1016/j.envres.2009.1

tissue according to the Banff 97 classification (Racusen et al., 1999). Generally,

20–50 glomeruli were seen in the cortical tissue, and small arteries were present

in most samples. In 109 of the 126 subjects with a biopsy (87%), part of the fresh

kidney cortex sample was transferred into pre-weighed acid-washed glass tubes

and frozen, and later analyzed for contents of heavy metals. In the other 17

subjects, the biopsy material could not be used for analysis of heavy metal

concentrations.

2.3. Determination of metal concentrations

The kidney samples were analyzed at the Department of Occupational and

Environmental Medicine at the University Hospital of Lund. The dry weights of all

samples were determined after drying at 80 1C for 1.5 h in a thermostat-controlled

cupboard. The dry weights of the samples (N=109) varied between 0.04 and 10 mg

(median 0.8 mg). After the samples had been dried, 0.10 mL of concentrated nitric

acid (Airstar, BDH laboratory supplies, Pool, Dorset, UK) was added and the

samples were digested for 3 h at 70 1C. Further preparation of the samples was in

principle the same as described in Barregard et al. (1999). Cadmium and lead

concentrations were determined by inductively coupled plasma-mass spectro-

metry (ICP-MS; Thermo X7, Thermo Elemental, Winsford, UK) (Barany et al.,

1997). Total mercury was determined by cold vapor atomic fluorescence

spectrometry (CVAFS) (Sandborgh-Englund et al., 1998). The samples were

analyzed in four different rounds. The calculated detection limits (three times

the SD for the blank) were 0.05, 0.03, 0.03, and 0.03 ng for cadmium, 0.16, 0.15,

0.06, and 0.02 ng for lead, and 0.23, 0.26, 0.83, and 0.19 ng for mercury,

respectively, for the different rounds. An external quality control sample

(BCR No. 186, Lyophilized pig kidney, Certified Reference Material, Community

Bureau of Reference—BRC, Brussels, Belgium) was analyzed six times in each

round to check for accuracy. The results for cadmium (2.58 mg/g [SD 0.10], 2.52 mg/

g [SD 0.06], 2.47 mg/g [SD 0.03], 2.45 [SD 0.08] mg/g), lead (0.31 mg/g [SD 0.05],

0.29 mg/g [SD 0.04], 0.29 mg/g [SD 0.02], 0.29 [SD 0.03] mg/g), and mercury

(1.91 mg/g [SD 0.09], 1.94 mg/g [SD 0.09], 1.75 mg/g [SD 0.04], 1.70 [SD 0.10] mg/g),

were in accordance with the target values of 2.71 mg/g for cadmium, 0.31 mg/g for

lead, and 1.97 mg/g for mercury. The dry weight metal concentrations were

transformed to wet weight concentrations by multiplying by 0.18 (Barregard et al.,

1999; Elinder et al., 1990).

The kidney weight for each subject was estimated from body surface area

(Kasiske and Umen, 1986). The estimated kidney weights were multiplied by the

concentrations of metals in the kidney to obtain the estimated total amount of

metals in the kidney.

Biopsy Women MenN=109 N=60 N=49

51 (24–70) 50 (24–64) 52 (32–70)

41 22 19

68 38 30

27 14 13

41 24 17

11 0 11

98 60 38

106 57 49

3 3 0

14 9 5

42 25 17

33 17 16

20 9 11

98 54 44

7 4 3

74 (49–111) 69 (49–95) 80 (65–111)

327 (248–423) 306 (248–376) 349 (300–423)

lead in kidney cortex of living kidney donors: Impact of different0.010

ARTICLE IN PRESS

L. Barregard et al. / Environmental Research ] (]]]]) ]]]–]]] 3

2.4. Exposure sources

A questionnaire was used to evaluate exposure to Cd, Hg, and Pb, including

questions on occupation, lifelong smoking habits, and diet (fish, vegetables, and

water supply). The total number of amalgam surfaces was counted, as well as the

number of occlusal surfaces.

Sixty percent of the donors were former or active smokers, and 98%

had amalgam fillings with a median of 20 filled surfaces in the total group and

19 in the biopsy group. About 20% consumed fish more than once a week. Three

donors were vegetarians. Background factors were found to be similar for the 109

kidney donors in whom heavy metals could be determined in kidney biopsies

(Table 1).

Among the 152 donors, 18 subjects (16 male and 2 female) had definite or

probable occupational exposure (in the following phrased as ‘‘exposure’’) to

cadmium, mercury, and/or lead (Table 1). Two of them had been exposed to

cadmium, six had low grade exposure to mercury or exposure to mercury that had

ceased more than 10 years ago at the time of investigation, five had daily exposure

to lead, and another 10 had been exposed to lead but only intermittently (low

grade exposure). In the biopsy group, only 11 subjects (all male) had been

occupationally exposed. One of these, a smoker, had worked as a smelter with

occupational exposure to cadmium, lead, and mercury for 6 years in the 1980s. He

was the only subject in the biopsy group with occupational exposure to cadmium.

Four other subjects had also been exposed to lead; one as a metal foundry worker

Table 2Kidney levels in mg/g (wet weight) of cadmium, mercury, and lead in 109 living kidne

Kidney Cd SmokingAll

Ever

AllN 109 68

Mean 15.0 17.9

Median 12.9 16.7

Range 1.5–55.4 1.5–55.4

WomenN 60 38

Mean 17.1 20.1

Median 14.7 18.6

Range 1.5–55.4 1.5–55.4

MenN 49 30

Mean 12.5 15.0

Median 10.9 15.6

Range 1.6–31.7 3.1–31.7

DL=detection limit.

Fig. 1. Kidney cadmium levels (mg/g wet weight) in m

Please cite this article as: Barregard, L., et al., Cadmium, mercury, andexposure sources,. Environ. Res. (2009), doi:10.1016/j.envres.2009.1

and three as book printers. Another six subjects had low grade lead exposure. Four

had low grade mercury exposure; these all also had amalgam fillings.

2.5. Statistics

Since kidney levels of Cd, Hg, and Pb were somewhat skewed, group

differences were assessed using the Wilcoxon rank sum test. Predictors of kidney

metal concentrations were evaluated with multiple linear regression using both

untransformed and log-transformed kidney metal levels.

3. Results

Kidney metal concentrations in women and men are shown inTable 2.

3.1. Cadmium

The geometric mean (GM) kidney Cd was 11.8 mg/g (14.1 inwomen and 9.5 in men) and the geometric standard deviation

y donors.

Kidney Hg Kidney Pb

Never

41 109 109

10.4 0.32 0.18

8.3 0.21 0.08

1.6–30.3 oDL-2.4 oDL-2.2

22 60 60

12.0 0.40 0.20

10.5 0.25 0.07

3.0–27.9 oDL-2.4 oDL-2.2

19 49 49

8.5 0.23 0.15

5.6 0.18 0.08

1.6–30.3 4DL–1.2 4DL–1.2

en and women as a function of age and smoking.

lead in kidney cortex of living kidney donors: Impact of different0.010

ARTICLE IN PRESS

L. Barregard et al. / Environmental Research ] (]]]]) ]]]–]]]4

(GSD) was 2.1. The difference between genders was statisticallysignificant (p=0.01). The total estimated kidney Cd (concentra-tionnestimated kidney weight) amount was higher in women(mean 5.2, median 4.6 mg) than in men (mean 4.4, median 4.0 mg).

The difference in kidney Cd between female never-smokers(median 10.5 mg/g) and ever-smokers (median 18.6 mg/g) wasstatistically significant (p=0.001), and so was the differencebetween male never-smokers (median 5.6 mg/g) and ever-smo-kers (median 15.6 mg/g) (p=0.001).

There was also a strong effect of cumulative smoking asexpressed in number of pack-years, and Cd levels were positivelyassociated with age in both never-smokers and ever-smokers,although levels seemed to decline after 65 years of age (Fig. 1).Moreover, Cd levels were negatively associated with body weight.

Female never-smokers had higher Cd levels than malenever-smokers (p=0.03) (Fig. 2). The impact of low iron storesin women was assessed by serum ferritin levels. When stratifiedby serum ferritin (o30 or Z30 mg/L), the median kidney Cd infemale never-smokers with low serum ferritin (n=10) was13.0 mg/g (range 5.4–27.9 mg/g) as compared to 8.2 mg/g (range3.0–22.6 mg/g) in female never-smokers with normal serumferritin (n=12) (Fig. 2).

Fig. 2. Kidney cadmium levels (mg/g wet weight, medians, 25th and 75th percent

never-smokers are also stratified for iron stores (serum ferritin o30 mg/L vs. Z30 mg/

Fig. 3. Kidney mercury levels (mg/g wet weight) in livin

Please cite this article as: Barregard, L., et al., Cadmium, mercury, andexposure sources,. Environ. Res. (2009), doi:10.1016/j.envres.2009.1

We tested regression models including age, sex, number ofpack-years, low iron stores in women (serum ferritin category),and body weight (stepwise selection). Subjects above 65 years ofage were excluded in these models since a decrease of kidneycadmium at old age is to be expected (Elinder et al., 1976).A model including only age, sex, and pack-years showedstatistically significant contributions of all these factors foruntransformed kidney Cd (R2=0.34), while the impacts of ironstores and body weight were not statistically significant. How-ever, with a model for log Cd (R2=0.41), age, pack-years, ironstores, and body weight were significant determinants, while sexwas not. With estimated total kidney Cd as the dependentvariable, eliminating the negative impact of body weight, therewere significant effects of age, pack-years, and iron stores, but notsex. This was also the case with log total kidney Cd as thedependent variable. Excluding the former smelter worker did notaffect the results given above.

Noting that the effects of age and pack-years were obvious inall models, but that it was unclear whether lower iron stores andlower body weight (both tending to increase kidney Cd) couldcompletely explain higher kidney Cd in women, we comparedkidney Cd levels and total kidney Cd (in mg) in non-smoking men

iles) in living kidney donors, stratified by sex and smoking habits. Levels for

L).

g kidney donors vs. number of amalgam surfaces.

lead in kidney cortex of living kidney donors: Impact of different0.010

ARTICLE IN PRESS

L. Barregard et al. / Environmental Research ] (]]]]) ]]]–]]] 5

(n=16) and women (n=12) with normal iron stores, both groupshaving a mean age of 50 years. The cadmium concentrations andthe total Cd amounts were still slightly higher in women,although the differences were not statistically significant.

Based on this, we selected two models for kidney Cdconcentrations (excluding subjects older than 65 years): model#1 including age, pack-years, and sex; and model #2 includingage (adjusted as above), pack-years, iron stores, and body weight.In model #1 (Adj R2=0.34), kidney Cd increased by 3.1 mg/g (SE0.8 mg/g, po0.001) for a 10 year increase in age, by 4.1 mg/g(SE 0.7 mg/g, po0.001) for an extra 10 pack-years, and by 5.0 mg/g(SE 1.6, po0.001) for female sex. In model #2 (Adj R2=0.37),kidney Cd increased by 3.9 mg/g (SE 0.9 mg/g, po0.001) for a 10year increase in age, by 3.7 mg/g (SE 0.7 mg/g, po0.001) for anextra 10 pack-years, by 4.5 mg/g (SE 2.0, p=0.03) for low ironstores in women, and by 1.3 mg/g (SE 0.6 mg/g, p=0.03) for a 10kilo decrease in body weight.

3.2. Mercury

The difference between females and males in kidney Hg(medians 0.25 and 0.18 mg/g, Table 2) was not statisticallysignificant. The estimated total kidney Hg was 76 mg in womenand 61 mg in men (medians).

Kidney mercury levels increased with total number ofamalgam fillings (rs=0.62, po0.001; Fig. 3). In a multiple linearregression analysis, log kidney Hg was positively and significantlyassociated with the total number of amalgam surfaces (po0.001),but not with age, sex, weight, or fish consumption. Kidneymercury increased by about 6% with every additional amalgamsurface. The results were similar after excluding subjects withprobable or low occupational exposure. They were also similarusing total kidney Hg as the dependent variable (6% increase peramalgam surface).

3.3. Lead

There were no differences between men and women in kidneyPb levels (medians 0.08 and 0.07 mg/g), and a multiple linearregression analysis showed no effect of smoking, age, or bodyweight. There was also no correlation between kidney Pb andeither number of pack-years or years of smoking. Excludingsubjects with occupational exposure did not change the results,and the results were also similar with total kidney Pb as thedependent variable.

Table 3Geometric mean cadmium in kidney cortex (mg/g, wet weight), and number of subject

Present study Elinder

W M NS W

Age

30–39 8 (10) 7 (8) 5.7 (9) 19

40–49 14 (15) 9 (11) 8.4 (6) 26

50–59 17 (23) 9 (21) 8.2 (16) 21

60–69 15 (9) 13 (8) 11.6 (8) 19

30–69d 14 (39) 9 (48) 8.1 (39) 21

W=women, M=men, NS=never-smokers.

a There was only one donor 469 and three donors o30 years of age.b There was only one never-smoker in each of these age strata.c Because there was only one female in this stratum in the study by Friis et al. (1998

in this stratum.d The results from the two autopsy studies were used to calculate average Cd conce

present study.

Please cite this article as: Barregard, L., et al., Cadmium, mercury, andexposure sources,. Environ. Res. (2009), doi:10.1016/j.envres.2009.1

4. Discussion

This is, to the best of our knowledge, the largest study providingchemical determinations of metals in the kidneys of living subjects.A strength of the study is the fact that the information on smoking,occupation, and diet should be more valid and precise than thatobtained in autopsy series. Nevertheless, the findings are largelyconsistent with previously published Swedish autopsy studies(Elinder et al., 1976; Nylander and Weiner, 1991; Friis et al., 1998).This indicates that the over-selection of individuals with suddendeath or certain diseases in autopsy studies does not seriouslyinvalidate their representativeness of the general populationregarding metal concentrations in the kidney. An interestingfinding is the clear increase of kidney cadmium with low ironstores, indicating that this is the major reason for higher kidneycadmium levels in female vs. male non-smokers.

4.1. Cadmium

The median kidney cadmium level in this study was lowerthan in a previous smaller study on living kidney donors inSweden (Barregard et al., 1999), but similar to results in a Swedishautopsy study from the 1990s (Friis et al., 1998). A Swedishautopsy study from the 1970s reported higher kidney Cd levelsthan the present study (Elinder et al., 1976; see Table 3). Thedecrease in kidney Cd levels compared to previous studies wasmost pronounced in age groups below 50 years of age (subjectsborn in the 1950s or later). However, much of this decrease willhave been caused by higher smoking rates in the previous studies(Elinder et al., 1976; Friis et al., 1998). The kidney Cd levels innever-smokers were similar to or only marginally lower thanthose from the 1970s (Table 3). It is therefore unclear whether thedietary contribution to kidney Cd has decreased. According todietary surveys, there has been no clear decrease in Cd intakeduring the 1990s (Jorhem et al., 2001), and kidney Cd levels do noteasily show such changes owing to the long half-life of kidney Cd.A study by Wennberg et al. (2006) revealed that theconcentrations of cadmium in the erythrocytes in Swedish menand women decreased significantly between 1990 and 1999 insmoking men only, while there was no such time trend in non-smoking men or in women.

Median kidney cadmium levels were similar in female andmale ever-smokers, but higher in female never-smokers than inmale never-smokers (Table 2, Fig. 2). This is likely to be caused bythe increased gastrointestinal absorption of dietary cadmium in

s within parentheses, in 71 living Swedish kidney donors aged 30–69 years.a

et al. (1976) Friis et al. (1998)

M NS W M NS

17 –b 8 7 5.5 (6)

19 –b 17 12 6.8 (4)

16 9.6(6) 16 13 6.9 (8)

17 13.5(11) 14c 10 6.2 (7)

17 15 11 6.4

), we used the average for women 50–79 years of age (N=25) to estimate kidney Cd

ntrations for women and men weighted with respect to the age distribution in the

lead in kidney cortex of living kidney donors: Impact of different0.010

ARTICLE IN PRESS

L. Barregard et al. / Environmental Research ] (]]]]) ]]]–]]]6

women with low body iron stores, as has previously been shownfor urinary and blood cadmium levels (Berglund et al., 1994;Olsson et al., 2002). In Sweden, about 10–40% of women of fertileage have depleted or no iron stores (Jarup et al., 1998). Previousstudies have usually found higher levels of cadmium in blood,urine, and the kidney in women than in men (Jarup et al., 1998).However, our results indicate that when iron stores and bodyweight are taken into account, there is no longer a sex difference.The negative influence of body weight in our regression models islikely to reflect the fact that, on average, kidney weight isassociated with body weight. The average kidney weight in men is15–20% higher than in women (Table 1). This was also illustratedby the fact that when total kidney Cd (in mg) was analyzed, theinfluence of body weight was lost, as was part of the differencebetween men and women.

The mean kidney cadmium level in the present study wasabout 8 mg/g higher in ever-smokers than in never-smokers. Theeffect of smoking obviously depends on the amount of smoking aswell as the Cd content in tobacco. In the present study, anadditional 10 pack-years resulted in an increase of 4 mg/g ofkidney Cd, which is lower than the estimate by Elinder et al.(1976) of 6 mg/g for 10 pack-years. This may reflect a decreased Cdcontent in cigarettes smoked in Sweden. In the ex-smokers,limited elimination of smoking-related Cd in the kidney may haveoccurred, but a stratified analysis of current smokers and ex-smokers showed a similar increase per pack-year.

The kidney Cd levels in the present study were slightly lowerthan those reported from several other countries. In the agegroup 40–60 years, the geometric mean kidney level in the 1980swas 15–20 mg/g in the UK (Lyon et al., 1999) and 20 mg/g inGermany (Hahn et al., 1987). The arithmetic mean in the 1990swas about 20 mg/g in Greenland (Johansen et al., 2006), 20–25 mg/g in Spain (Torra et al., 1995) as well as in Australia (Satarug et al.,2002). Higher kidney Cd levels were reported in Poland (Orlowskiet al., 1998), and much higher levels in Japan (Honda and Nogawa,1987; Koizumi et al., 2008).

Assuming a log-normal distribution, and that the GM and GSDin the present group are representative of the general Swedishadult population, 3% of women and 2% of men have kidney Cdabove 50 mg/g. Kidney Cd below this level was previouslyconsidered relatively safe in terms of the risk of renal tubulardamage, assuming that kidney Cd 50 mg/g corresponds to urinaryCd (U–Cd) of about 2.5 mg/g creatinine (Elinder and Nordberg,1998). However, in recent decades, increased urinary calcium hasbeen shown at lower levels of U–Cd (Buchet et al., 1990), andincreased excretion of renal tubular proteins has been reportedwith U–Cd levels as low as 0.5–1 mg/g (Akesson et al., 2005; Jarupet al., 2000). Bone mineral density has been found to decrease andthe risk of fractures increase at low-level cadmium exposure(Akesson et al., 2006; Alfven et al., 2000, 2004). Therefore, kidneylevels lower than 50 mg/g may also represent an increased risk forearly adverse effects on kidney and bone. It should also be notedthat the estimates of relations between urinary cadmium andkidney cadmium are uncertain (Elinder and Nordberg, 1998;Orlowski et al., 1998). Hopefully, we will soon be able tocontribute to this question using simultaneous determinationsof kidney Cd and U–Cd in the living kidney donors.

4.2. Mercury and lead

The average kidney Hg level in the present study, 0.2 mg/g, wasabout twice that found in German autopsy studies (Drasch et al.,1992, 1996). The reason for this is probably a higher averageamalgam load in Sweden than in Germany; a small Swedishautopsy study showed a median kidney Hg of 0.18 mg/g (Nylander

Please cite this article as: Barregard, L., et al., Cadmium, mercury, andexposure sources,. Environ. Res. (2009), doi:10.1016/j.envres.2009.1

and Weiner, 1991). Another result of the present study was thatfish consumption appeared to have no impact. Although it is likelythat the kidney accumulates some inorganic mercury, formed bydemethylation of methyl mercury from fish, this is probablyovershadowed by the larger impact of inorganic Hg from dentalamalgam. However, a study from Greenland, where the intake ofmethyl mercury from seafood is high, revealed an average kidneyHg level of 1.4 mg/g (Johansen et al., 2007).

The variability in kidney Hg was considerable (GSD 4.0; Fig. 3),as has already been shown to be the case for urinary Hg(Barregard, 2005; Barregard et al., 1995; Sallsten et al., 1996).Again assuming a log-normal distribution, 3% of the Swedishpopulation would have a kidney Hg 42 mg/g. Since the major partof kidney Hg has a half-life of about 2 months (Sallsten et al.,1994), kidney Hg levels should reflect the last year’s exposure toinorganic Hg. The slightly higher kidney Hg in women than in menseems to reflect the fact that the female kidney is smaller onaverage, since the difference disappeared when kidney weight wastaken into account.

The lead concentrations in donor kidneys were lower thanreported in autopsy studies (Bahemann-Hoffmeister et al., 1988;Brune et al., 1980; Gerhardsson et al., 1986, 1995). However, leadexposure has decreased substantially in Sweden in recent decades(Stromberg et al., 2008), and this should have resulted in reducedkidney lead as well. It should be noted that the analyticalprecision is limited at these low lead levels in small samples.

4.3. Issues of validity

Although living donors should provide more valid backgrounddata than can be obtained in autopsy studies, kidney biopsiescarry the limitation of small sample size (fresh weight about5 mg). This may induce some imprecision if metal concentrationsare not uniform within the kidney cortex. Cadmium concentra-tions decrease from the outer to the inner layers of the kidneycortex (Livingstone, 1972). However, the biopsies were all takenfrom the outer part of the cortex in the lower kidney pole.Moreover, the GSD for kidney Cd in our study was 2.1, which issimilar to the GSD of 1.9 in the autopsy study by Elinder et al.(1976). This indicates that variability is not considerably larger fordonor biopsies than for autopsy samples.

Quality control indicated no contamination problems, as wellas adequate analytical performance when analyzing externalreference samples. Determination of cadmium in the externalquality control sample from pig kidney showed results wellwithin the accepted range but still slightly lower than the targetlevel, and we cannot exclude a slight underestimation of the truecadmium level. Kidney donors should be considered representa-tive of the healthy part of the Swedish general population.Inclusion as a donor requires normal kidney function and absenceof serious systemic disease, though the criteria are not very strict,as shown by the fact that the donors in the present study includedindividuals up to 70 years of age.

It is logical to present kidney metal burden as concentrations,as long as the impact of contaminated food in differentpopulations is compared or kidney burden is compared withrenal function. When comparing kidney Cd with the number ofcigarettes smoked or kidney Hg with the number of amalgamfillings, it is theoretically preferable to use the total amount ofmetal in the kidney, thus accounting for kidney weight. In thepresent study, kidney weights were not measured but estimatedfrom body surface. Nevertheless, the results were similar which-ever measure of kidney metal burden was used.

In summary, the present study shows that low iron stores areassociated with increased kidney Cd concentrations in women.

lead in kidney cortex of living kidney donors: Impact of different0.010

ARTICLE IN PRESS

L. Barregard et al. / Environmental Research ] (]]]]) ]]]–]]] 7

When iron stores and kidney weight are taken into account, thereseems to be no sex difference. Reduced smoking has decreasedkidney Cd in Sweden, while levels in never-smokers seem to bestable. Kidney Hg is mainly affected by the amount of dentalamalgam. Kidney Pb levels seem to have decreased, probably dueto lower lead exposure following the discontinuation of leadedgasoline.

Acknowledgments

We thank Professor Gunnar Westberg who participated in theinitial planning of the study, Magnus Akerstrom who helped withpart of the data collection, and Gunnel Garsell for technicalassistance.

References

Akesson, A., Lundh, T., Vahter, M., Bjellerup, P., Lidfeldt, J., Nerbrand, C., et al., 2005.Tubular and glomerular kidney effects in Swedish women with lowenvironmental cadmium exposure. Environ. Health Perspect. 113, 1627–1631.

Akesson, A., Bjellerup, P., Lundh, T., Lidfeldt, J., Nerbrand, C., Samsioe, G., 2006.Cadmium-induced effects on bone in a population-based study of women.Environ. Health Perspect. 114, 830–834.

Alfven, T., Elinder, C.G., Carlsson, M.D., Grubb, A., Hellstrom, L., Persson, B., 2000. Low-level cadmium exposure and osteoporosis. J. Bone Miner. Res. 15, 1579–1586.

Alfven, T., Jarup, L., Elinder, C.G., 2002. Cadmium and lead in blood in relation tolow bone mineral density and tubular proteinuria. Environ. Health Perspect.110, 699–702.

Alfven, T., Elinder, C.G., Hellstrom, L., Lagarde, F., Jarup, L., 2004. Cadmiumexposure and distal forearm fractures. J. Bone Miner. Res 19, 900–905.

Angerer, P., Kessel, R., Bencze, K., Tewordt, M., Mauermayer, R., Friesen, A., 1988. DerCadmiumgehalt bioptisch gewonnener menschlicher Gewebe [The cadmiumcontent of human tissues from biopsies]. Zbl. Bakt. Hyg. B 187, 18–30.

Bahemann-Hoffmeister, A., Kessel, R., Bencze, K., Tewordt, M., 1988. Leadconcentrations in human tissues with regard to habits and occupationalexposure. Zbl. Arbeitsmed. 38, 30–35.

Barany, E., Bergdahl, I.A., Schutz, A., Skerfving, S., Oskarsson, A., 1997. Inductivelycoupled plasma mass spectrometry for direct multi-element analysis ofdiluted human blood and serum. J. Anal. At. Spectrom. 12, 1005–1009.

Barregard, L., Sallsten, G., Jarvholm, B., 1995. People with high mercury uptakefrom their own dental amalgam fillings. Occup. Environ. Med. 52, 124–128.

Barregard, L., Svalander, C., Schutz, A., Westberg, G., Sallsten, G., Blohme, I., et al.,1999. Cadmium, mercury, and lead in kidney cortex of the general Swedishpopulation: a study of biopsies from living kidney donors. Environ. HealthPerspect. 107, 867–871.

Barregard, L., 2005. Mercury from dental amalgam: looking beyond the average.Occup. Environ. Med. 62, 352–353.

Berglund, M., Akesson, A., Nermell, B., Vahter, M., 1994. Intestinal absorption ofdietary cadmium in women depends on body iron stores and fiber intake.Environ. Health Perspect. 102, 1058–1066.

Brune, D., Nordberg, G., Wester, P.O., 1980. Distribution of 23 elements in thekidney, liver and lungs of workers from a smeltery and refinery in NorthSweden exposed to a number of elements and of a control group. Sci. TotalEnviron. 16, 13–35.

Buchet, J.P., Lauwerys, R., Roels, H., Bernard, A., Bruaux, P., Claeys, F., et al., 1990.Renal effects of cadmium body burden of the general population. Lancet 336,699–702.

De Burbure, C., Buchet, J.P., Leroyer, A., Nisse, C., Haguenoer, J.M., Mutti, A., et al.,2006. Renal and neurologic effects of cadmium, lead, mercury, and arsenic inchildren: evidence of early effects and multiple interactions at environmentalexposure levels. Environ. Health Perspect. 114, 584–590.

Drasch, G., Schupp, I., Riedl, G., Gunther, G.., 1992. Einfluss von Amalgamfullungenauf die Quecksilberkonzentration in menschlichen Organen. Dtsch. Zahnarzt.47, 490–496.

Drasch, G., Wanghofer, E., Roider, G., Strobach, S., 1996. Correlation of mercury andselenium in the human kidney. J. Trace Elem. Med. Biol. 10, 251–254.

Ekong, E.B., Jaar, B.G., Weaver, V.M., 2006. Lead-related nephrotoxicity: a review ofthe epidemiologic evidence. Kidney Int. 70, 2074–2084.

Elinder, C.-G., Kjellstrom, T., Lind, B., Linnman, L., 1976. Cadmium in kidney cortex,liver, and pancreas from Swedish autopsies. Arch. Environ. Health 31, 292–302.

Elinder, C.-G., Nordberg, M., Palm, B., 1990. Is cadmium released frommetallothionein in rejected human kidneys? Biol. Met. 2, 219–222.

Elinder C.-G., Nordberg G. 1998. Kidneys. In: Jarup, L., Berglund, M., Elinder, C.-G.,Nordberg, G., Vahter, M. (Eds.), Health Effects of Cadmium Exposure—AReview of the Literature and a Risk Estimate. Scand. J. Work Environ. Health24(suppl. 1), 1–52.

Ellingsen, D.G., Efskind, J., Berg, K.J., Gaarder, P.I., Thomassen, Y., 2000. Renal andimmunologic markers for chloralkali workers with low exposure to mercuryvapor. Scand. J. Work Environ. Health 26, 427–435.

Please cite this article as: Barregard, L., et al., Cadmium, mercury, andexposure sources,. Environ. Res. (2009), doi:10.1016/j.envres.2009.1

Ezaki, T., Tsukahara, T., Moriguchi, J., Furuki, K., Fukui, Y., Ukai, H., et al., 2003. Noclear-cut evidence for cadmium-induced renal tubular dysfunction amongover 10,000 women in the Japanese general population: a nationwide large-scale survey. Int. Arch. Occup. Environ. Health 76, 186–196.

Falnoga, I., Tusek-Znidaric, M., Horvat, M., Stegnar, P., 2000. Mercury, selenium,and cadmium in human autopsy samples from Idrija residents and mercurymine workers. Environ. Res. 84, 211–218.

Friis, L., Peterson, L., Edling, C., 1998. Reduced cadmium levels in human kidneycortex in Sweden. Environ. Health Perspect. 106, 175–178.

Gallagher, C.M., Kovach, J.S., Meliker, J.R., 2008. Urinary cadmium and osteoporosisin US women Z50 years of age: NHANES 1988–1994 and 1999–2004. Environ.Health Perspect. 116, 1338–1343.

Gerhardsson, L., Brune, D., Nordberg, G.F., Wester, P.O., 1986. Distribution ofcadmium, lead and zinc in lung, liver and kidney in long-term exposed smelterworkers. Sci. Total Environ. 50, 65–85.

Gerhardsson, L., Englyst, V., Lundstrom, N.G., Nordberg, G., Sandberg, S., Steinvall,F., 1995. Lead in tissues of deceased lead smelter workers. J. Trace Elem. Med.Biol. 9, 136–143.

Hahn, R., Ewers, U., Jermann, E., Freier, I., Brockhaus, A., Schlipkoter, H.W., 1987.Cadmium in kidney cortex of inhabitants of North-West Germany: itsrelationship to age, sex, smoking and environmental pollution by cadmium.Int. Arch. Occup. Environ. Health 59, 165–176.

Honda, R., Nogawa, K., 1987. Cadmium, zinc and copper relationships in kidneyand liver of humans exposed to environmental cadmium. Arch. Toxicol. 59,437–442.

Jarup, L., Berglund, M., Elinder, C.-G., Nordberg, G., Vahter, M., 1998. Health effectsof cadmium exposure—a review of the literature and a risk estimate. Scand. J.Work Environ. Health 24 (suppl. 1), 1–52.

Jarup, L., Hellstrom, L., Alfven, T., Carlsson, M.D., Grubb, A., Persson, B., 2000. Lowlevel exposure to cadmium and early kidney damage: the OSCAR study. Occup.Environ. Med. 57, 668–672.

Jarup, L., 2002. Cadmium overload and toxicity. Nephrol. Dial. Transplant. 17(suppl. 2), 35–39.

Johansen, P., Mulvad, G., Pedersen, H.S., Hansen, J.C., Riget, F., 2006. Accumulation ofcadmium in livers and kidneys in Greenlanders. Sci. Total Environ. 372, 58–63.

Johansen, P., Mulvad, G., Pedersen, H.S., Hansen, J.C., Riget, F., 2007. Humanaccumulation of mercury in Greenland. Sci. Total Environ. 377, 173–178.

Jorhem, L., Sundstrom, B., Engman, J., 2001. Cadmium and other metals in Swedishwheat and rye flours: longitudinal study, 1983–1997. J. AOAC Int. 841984–1992

Kasiske, B.L., Umen, A.J., 1986. The influence of age, sex, race, and body habitus onkidney weight in humans. Arch. Pathol. Lab. Med. 110, 55–60.

Kazantzis, G., Schiller, K.F.R., Asscher, A.W., Drew, R.G., 1962. Albuminuria and thenephrotic syndrome following exposure to mercury and its compounds. Q. J.Med. 31, 409–413.

Koizumi, N., Murata, K., Hayashi, C., Nishio, H., Goji, J., 2008. High cadmiumaccumulation among humans and primates: comparison across variousmammalian species—a study from Japan. Biol. Trace Elem. Res. 121, 205–214.

Livingston, H.D., 1972. Measurement and distribution of zinc, cadmium, andmercury in human kidney tissue. Clin. Chem. 18, 67–72.

Lyon, T.D., Aughey, E., Scott, R., Fell, G.S., 1999. Cadmium concentrations in humankidney in the UK: 1978–1993. J. Environ. Monit. 1, 227–231.

Nylander, M., Weiner, J., 1991. Mercury and selenium concentrations and theirinterrelations in organs from dental staff and the general population. Br. J. Ind.Med. 48, 729–734.

Olsson, I.M., Bensryd, I., Lundh, T., Ottosson, H., Skerfving, S., Oskarsson, A., 2002.Cadmium in blood and urine—impact of sex, age, dietary intake, iron status,and former smoking—association of renal effects. Environ. Health Perspect.110, 1185–1190.

Orlowski, C., Piotrowski, J.K., Subdys, J.K., Gross, A., 1998. Urinary cadmium asindicator of renal cadmium in humans: an autopsy study. Hum. Exp. Toxicol.17, 302–306.

Osman, K., Elinder, C.-G., Schutz, A., Grubb, A., 1999. Biomarkers of nephrotoxicity inchildren environmentally exposed to lead in Poland. J. Environ. Med 1, 33–38.

Racusen, L.C., Solez, K., Colvin, R.B., Bonsib, S.M., Castro, M.C., Cavallo, T., et al.,1999. The Banff 97 working classification of renal allograft pathology. KidneyInt 55, 713–723.

Sandborgh-Englund, G., Bjorkhem, I., Bjorkman, L., Valtersson, C., 1998. Determi-nation of low levels of total mercury in blood and plasma by cold vapouratomic fluorescence spectrometry. Scand. J. Clin. Lab. Invest. 58, 155–160.

Schutte, R., Nawrot, T.S., Richart, T., Thijs, L., Vanderschueren, D., Kuznetsova, T., et al.,2008. Bone resporption and environmental exposure to cadmium in women: apopulation study. Environ. Health Perspect. 116, 777–783.

Sallsten, G., Barregard, L., Schutz, A., 1994. Clearance half life of mercury in urineafter the cessation of long term occupational exposure: influence of a chelatingagent (DMPS) on excretion of mercury in urine. Occup. Environ. Med. 51,337–342.

Sallsten, G., Thoren, J., Barregard, L., Schutz, A., Skarping, G., 1996. Long-term use ofnicotine chewing gum and mercury exposure from dental amalgam fillings.J. Dent. Res. 75, 594–598.

Satarug, S., Baker, J.R., Reilly, P.E., Moore, M.R., Williams, D.J., 2002. Cadmiumlevels in the lung, liver, kidney cortex, and urine samples from Australianswithout occupational exposure to metals. Arch. Environ. Health 57, 69–77.

Staessen, J.A., Lauwerys, R.R., Ide, G., Roels, H.A., Vyncke, G., Amery, A., 1994. Renalfunction and historical environmental cadmium exposure from zinc smelters.Lancet 343, 1523–1527.

lead in kidney cortex of living kidney donors: Impact of different0.010

ARTICLE IN PRESS

L. Barregard et al. / Environmental Research ] (]]]]) ]]]–]]]8

Staessen, J.A., Roels, H.A., Emelianov, D., Kuznetsova, T., Thijs, L., Vangronsveld, J.,

et al., 1999. Environmental exposure to cadmium, forearm bone density,

and risk of fractures: prospective population study. Public Health and

Environmental Exposure to Cadium (PheeCad) Study Group. Lancet 353,

1140–1144.

Stromberg, U., Lundh, T., Skerfving, S., 2008. Yearly measurements or blood lead in

Swedish children since 1978: the declining trend continues in the petrol-lead-

free period 1995–2007. Environ. Res. 107, 332–335.

Thomas, L.D., Hodgson, S., Nieuwenhuijsen, M., Jarup, L., 2009. Early kidney

damage in a population exposed to cadmium and other heavy meals. Environ.

Health Perspect. 117, 181–184.

Torra, M., To-Figueras, J., Rodamilans, M., Brunet, M., Corbella, J., 1995. Cadmium

and zinc relationships in the liver and kidney of humans exposed to

environmental cadmium. Sci. Total Environ. 170, 53–57.

Please cite this article as: Barregard, L., et al., Cadmium, mercury, andexposure sources,. Environ. Res. (2009), doi:10.1016/j.envres.2009.1

Vahter M., 1982. Assessment of human exposure to lead and cadmium throughbiological monitoring. UNEP/WHO Final Report, National Swedish Institute ofEnvironmental Medicine and Karolinska Institute, Stockholm.

Wennberg, M., Lundh, T., Bergdahl, I.A., Hallmans, G., Jansson, J.H., Stegmayr, B., et al.,2006. Time trends in burdens of cadmium, lead, and mercury in the population ofnorthern Sweden. Environ. Res. 100, 330–338.

World Health Organization (WHO), 1991. Inorganic mercury. EnvironmentalHealth Criteria, vol. 118. WHO, Geneva.

World Health Organization (WHO), 1992. Cadmium. Environmental HealthCriteria, vol. 134. WHO, Geneva.

World Health Organization (WHO), 1995. Inorganic lead. Environmental HealthCriteria, vol. 165. WHO, Geneva.

Wu, X., Jin, T., Wang, Z., Ye, T., Kong, Q., Nordberg, G., 2001. Urinary calcium as abiomarker of renal dysfunction in a general population exposed to cadmium.J. Occup. Environ. Med. 43, 898–904.

lead in kidney cortex of living kidney donors: Impact of different0.010