Ecotoxicology and Environmental Safety 73 (2010) 1433–1439

Contents lists available at ScienceDirect

Ecotoxicology and Environmental Safety

0147-65

doi:10.1

n Corr

E-m

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

Monitoring of pesticide residues in vegetables marketed inAl-Qassim region, Saudi Arabia

K.A. Osman a,n, A.M. Al-Humaid b, S.M. Al-Rehiayani b, K.N. Al-Redhaiman b

a Department of Pesticide Chemistry & Toxicology, College of Agriculture, El-Chatby, P.O. Box 21545, Alexandria University, Egyptb Department of Plant Production & Protection, College of Agriculture & Veterinary Medicine, Qassim University, Buraidah 51452, P.O. Box 6622, Saudi Arabia

a r t i c l e i n f o

Article history:

Received 4 October 2009

Received in revised form

9 May 2010

Accepted 19 May 2010Available online 8 June 2010

Keywords:

Pesticide

Residues

Vegetables

Solid phase extraction

Gas chromatography

Qassim

13/$ - see front matter & 2010 Elsevier Inc. A

016/j.ecoenv.2010.05.020

esponding author. Fax: +96663801360.

ail address: Kamosman@yahoo.com (K.A. Osm

a b s t r a c t

A total of 23 pesticides from different chemical groups in 160 different domestic vegetables collected

from four major big supermarkets located in Al-Qassim region, Saudi Arabia, were identified by gas

chromatography with mass spectrometry (GC–MS). Residues were found in 89 of the 160 samples and

53 samples were above the maximum residue levels (MRLs). The most frequently found pesticides were

carbaryl followed by biphenyl and then carbofuran. Cabbage was the most positive and violated MLRs

(16 and 11 samples), followed by carrot and green pepper (12 and 7 samples), cucumber (12 and 6

samples), egg-plant (12 and 5 samples), squash (11 and 7 samples), lettuce (11 and 6 samples) and

tomato (11 and 4 samples). The highest concentrations were found in lettuce (ethiofencarb, 7.648),

followed by tomato (tolclofos-methyl, 7.312 mg/kg), cabbage (chlropyrifos, 6.207 mg/kg), carrot

(heptanophos, 3.267 mg/kg), green pepper (carbaryl, 2.228 mg/kg) and egg-plant (carbaryl, 1.917 mg/

kg). These findings pointed to the following recommendation: the need for a monitoring program for

pesticide residues in vegetables cultivated under greenhouse conditions at the national level to protect

consumers’ health.

& 2010 Elsevier Inc. All rights reserved.

1. Introduction

The use of pesticides is essential to control pests inhorticultural crops for the production of an adequate food supplyfor an increasing world population and for the control of insect-borne diseases. These pesticides are used to decrease crop lossboth before and after harvest (Clarke et al., 1997). Pesticideresidues in food and crops are a direct result of application ofpesticides to crops growing in the field, and to a lesser extent frompesticide residues remaining in the soil (Businelli et al., 1992).However, many pesticides are toxic substances and persistent incharacter. There is a growing social desire to reduce the use ofpesticides in agriculture and horticulture (Freidberg, 2003; Prettyand Hine, 2005). Supermarkets are under increasing pressure toadapt to a changing consumer preference that perceives pesti-cides as an undesirable component of food production. Whenseeking to rationalize pesticide use, both government (CouncilDirective, 1990) and supermarkets have tended to make theimplicit assumption that any rationalization is primarily an issueof decreasing the quantity of pesticides used, coupled with thebanning of specific, highly toxic substances (Freidberg, 2003;Gallivan et al., 2001; Levitan, 2000). Thus, pesticides with hightoxicity to humans are targeted for rationalization, irrespective of

ll rights reserved.

an).

the quantity used. Such actions may not reflect the actual riskto humans or the full hazard profile of the pesticide. For thesereasons, decisions as to which pesticides to target for reductioncan be problematic unless they are made with full knowledge oftheir relative toxicological properties, environmental fate andmobility (Kovach et al., 1992; Levitan, 2000).

Monitoring of pesticide residues in vegetables for an extensiveevaluation of vegetable quality is a priority objective of pesticideresearch to avoid possible risks to human health. Highly sensitiveand selective analytical procedures to determine residues of thesecompounds in a variety of food matrices have been developed.Gas chromatographic methods with mass spectrometric detection(GC–MS) have been used successfully for the analysis of manyvolatile pesticides and they offer simultaneous quantitation andconfirmation of a large number of pesticides, excellent separationefficiency, high speed of analysis, and the wide range of sensitiveand selective detectors available. Several multiresidue methodsfor determination of organophosphorus, organochlorine andorganonitrogen pesticides in crops using gas chromatographyfor separation of individual compounds, followed by detectionwith selective and sensitive detectors have been proposed(Andersson and Palsheden, 1991; Specht et al., 1995; Stan,2000; Albero et al., 2003; Pugliese et al., 2004; Rial-Otero et al.,2005; Pose-Juan et al., 2006, 2009; Balinova et al., 2007; Berradaet al., 2010; Menezes Filho et al., 2010).

To protect consumer’s health, many countries have estab-lished legal directives to control levels of pesticides in food,

K.A. Osman et al. / Ecotoxicology and Environmental Safety 73 (2010) 1433–14391434

through maximum residue levels, MRLs (FAO/WHO, 2004; CouncilDirective, 2003). The levels of pesticide residues in foodstuffsare generally legislated so as to minimize the exposure of theconsumer to harmful or unnecessary intakes of pesticides, toensure the proper use of pesticides in terms of granted authoriza-tion and registration (application rates and pre-harvested inter-vals) and to permit the free circulation of pesticide-treatedproducts, as long as they comply with the fixed MRLs. Violativeresidues occur when pesticide residues are detected that exceedthe allowable level known as the tolerance that is establishedspecifically for a particular pesticide on a particular food item. Themore common form of violative residues, however, occurs in caseswhen residues are detected on a food item for which a tolerancehas not been established. Tolerances are not barometers of levelsof health concern but represent the maximum residues anticipatedfrom legal use of pesticides (Winter, 1992). Exposure is a factor ofboth the amount of consumption of the various food items as wellas the actual levels of residues occurring on food; violation rates orpresence/absence data do not consider these important exposurefactors (Katz and Winter, 2009).

No data are available on the levels of pesticide residues invegetables sold in local markets of Al-Qassim region, Saudi Arabia(KSA). Therefore, the present study was undertaken to monitorpesticide residues in vegetables grown under greenhouse condi-tions collected from the big supermarkets located in Al-Qassimregion to provide background information on the levels of theseresidues in this region. Sensitive, versatile and selective multi-residue method for the quantitative determination of pesticidesfrom several compound classes using GC–MS detection wasemployed. Besides, the study also was determining the currentlevel of exposure of the local population of Al-Qassim tohazardous pesticides by eating raw of the pesticide-contained.

2. Materials and methods

2.1. Samples collection

A total of 160 vegetable samples were collected during the period of October

2008–January 2009 from four major big supermarkets located in Al-Qassim region,

KSA. A minimum of five samples (the sample size of each commodity ranged from

Table 1The usage, chemical group, molecular weight, retention times and fragment ions selec

Pesticide Use Chemical group

Amitrole Herbicide Triazole

Azobenzene Acaricide Azobenzene

Bioallethrin Insecticide Pyrethroid

Biphenyl Fungicide Aromatic hydrocarbon

Bromoxynil Herbicide Hydroxybenzonitrile

Carbaryl Insecticide Carbamate

Carbofuran Nematicide Carbamate

Chlorpyrifos Insecticide Organophosphate

Dicofol Acaricide Organochlorine

Dieldirn Insecticide Organochlorine

ENT 92 Insecticide Thiocynate

Ethiofencarb Insecticide Carbamate

Heptenophos Insecticide Organophosphate

Lindane Insecticide Organochlorine

Malathion Insecticide Organophosphate

Metalaxyl Fungicide Phenylamide: acylalanine

Methoxychlor Insecticide Organochlorine

Paraquat Herbicide Bipyridylium

Propoxur Insecticide Carbamate

Pyrethrin I Insecticide Natural pyrethrin

Tefluthrin Insecticide Pyrethroid

Tolclofos-methyl Fungicide Organophosphate

Warfarin Rodenticide Coumarin anticoagulant

ENT 92 Insecticide Thiocynate

1 to 2 kg) were collected from the upper, middle, and lower shelves to give

representive sample, put in sterile polyethylene bags, and transported to the

laboratory where they were immediately analyzed.

2.2. Chemicals and materials

Pesticide standards were obtained from Environmental Protection Agency

(EPA, USA) with certified purities ranging from 95% to 99%. The tested pesticides,

their use and chemical group are listed in Table 1. Concentrations of standard

solutions were corrected for the certified purity of the standards. Methanol,

acetone and ethyl acetate (HPLC grades) were purchased from BDH Company, UK.

Ultra-pure deionized water of 15 MO cm resistivity was obtained from a water

purification system (PURELAB Option-R, ELGA, UK). Solid phase extraction column

(Waters speTM

, C18, Sep-Pak Vac, 500 mg per column, 6 cm3, with a surface area

1200 m2 g�1 and particle size 40–120 mm, Waters, USA) and a 20-port vacuum

manifold (Waters, USA) were employed for the clean up of the extracts.

2.3. Gas chromatography–mass spectrometry (GC–MS)

Gas chromatography (Model GC 450, Varian Inc., The Netherlands) with a mass

spectrometry (MS 200.41) detector equipped with split/splitless injector with

electronic pressure control was employed. A fused silica CP-Sil 8 CB-LB/MS capillary

column (30 m�0.25 mm i.d.) was used in combination with the following oven

temperature program: initial temperature 50 1C, held for 2 min, 20 1C min�1 ramp to

160 1C held for 2 min, followed by 3 1C min�1 to 300 1C held for 1 min. The carrier gas

(helium, 99.999%) flow rate was set to a constant head pressure of 200 kPa at flow rate

of 1 ml min�1. The mass spectrometer was operated in electron ionization mode with

a transfer line temperature of 280 1C, manifold temperature 40 1C, trap temperature

200 1C, filament number 2, ion source 230 1C and selected ion monitoring (SIM) mode.

The ion energy for electron impact (EI) was kept at 70 eV. MS Workstation version

6.9.1 was used for data acquisition. For positive identification, both retention time (Rt)

and the presence of three fragment ions were considered (Table 1).

2.4. Sample preparation

Samples were chopped and a subsample (10 g) was weighed into 50 ml Teflon

centrifuge tube and extracted with 20 ml acetone using a homogenizer

(Euroturrax, IKA Labortechnik Staufen, Germany) at full speed for 2 min. The

extract was centrifuged at 3000 rpm for 5 min and the supernatant was

transferred to a clean graduated cylinder (25 ml) to measure its volume.

2.5. Solid-phase extraction

Solid-phase extraction was carried out using SPE column according to

Stajnbaher and Zupancic-Kralj (2003) method. The extraction columns were

conditioned by passing 6 ml of ethyl acetate followed by 6 ml of methanol and

ted of the tested pesticides by GC–MS.

Rt (min) MW M/Z1 M/Z2 M/Z3

7.351 84 53 55 74

13.619 182 77 105 182

14.678 302 91 123 204

23.827 154 76 152 154

14.605 275 88 168 277

7.157 201 89 144 155

15.925 221 91 165 180

22.013 349 97 197 314

21.084 368 139 199 251

13.402 378 73 81 117

9.998 253 67 95 121

11.736 225 107 168 241

8.261 250 89 109 124

16.606 288 111 145 181

21.715 330 127 173 283

20.284 279 206 249 279

24.037 344 114 165 277

17.655 256 102 128 156

7.464 209 81 110 152

14.666 328 123 162 260

20.144 418 77 177 197

5.515 300 125 265 267

7.442 308 121 187 265

9.998 253 67 95 121

K.A. Osman et al. / Ecotoxicology and Environmental Safety 73 (2010) 1433–1439 1435

then 8 ml of ultra-pure deionized water. The sorbent was never allowed to dry

during the conditioning and sample loading steps. Then the extraction columns

were fitted with detachable 70-ml polypropylene reservoirs to contain the diluted

sample extract. Exactly one-half of the extract (equivalent to 5 g sample) was

transferred to the reservoir, which was partially filled with ultra-pure deionized

water and then water was added to the top. Sample loading was performed under

vacuum at flow rates of 5 ml min�1. After the passage of the extract, the column

was dried by vacuum aspiration under increased vacuum for 30 min. The pesti-

cides were eluted with 3�2 ml aliquots of ethyl acetate–acetone at the ratio of

90:10 (v/v). The eluates were collected in 10 ml tubes under gravity flow only.

After all the elution solvent had passed through the extraction column, the

residual solvent was forcibly removed from the column. The eluate was

evaporated to less than 1 ml using gentle stream of nitrogen and then the solvent

was exchanged to acetone by adding two 2-ml portions of acetone and evaporated

to low volume after each addition. The extract was quantitatively transferred to a

2 ml clean vials and completed with acetone to 1 ml.

2.6. Calibration curves

Individual stock solutions of pesticides (1 mg/ml) were prepared in acetone

and then serial dilutions ranging from 0.01 to 10 ng/ml were prepared using

acetone. Mixed compound calibration solutions in acetone were prepared with

concentrations disregarding their GC sensitivities and were used as spiking

solutions as well. The GC–MS system was standardized on the same day as the

samples were analyzed by injecting 2 ml of seven solutions of freshly prepared

standard pesticides in acetone. Areas under the peak versus concentrations were

plotted and fit by simple linear regression to obtain the equation for the standard

curves for the tested pesticides. The amount of each pesticide in each sample was

thus calculated based on the slope of the standard curve.

2.7. Recovery studies

Recovery tests were carried out using pesticide-free samples. A subsamples

of known blanks (10 g) were spiked prior to extraction by addition of

2 ml of composite pesticide standard solutions in acetone to give 0.05, 0.10

and 0.50 mg/kg of each compound. They were then prepared according to the

proposed procedure as described previously. Recovery and precision (expressed as

relative standard deviation) was measured by analyzing three samples of each type

of vegetable.

Table 2Maximum residue levels of the tested pesticides.

Pesticide Maximum residue levels, MRLs (mg/kg)a

Tomato Squash Cucumber Egg-

Amitrole 0.01 0.01 0.01 0.01

Azobenzene NS NS NS NS

Bioallethrin NS NS NS NS

Biphenyl NS NS NS NS

Bromoxynil 0.05 0.05 0.05 0.05

Carbaryl 0.50 0.05 0.05 0.05

Carbofuran 0.02 0.02 0.02 0.02

Chlorpyrifos 0.50 0.05 0.05 0.05

Dicofol 1 0.50 0.20 0.02

Dieldirn 0.0.1 0.03 0.02 0.01

ENT 92 NS NS NS NS

Ethiofencarb NS NS NS NS

Heptenophos NS NS NS NS

Lindane 0.01 0.01 0.01 0.01

Malathion 0.05 0.2 0.20 0.02

Metalaxyl 0.2 0.05 0.5 0.05

Methoxychlor 1 1 1 1

Paraquat 0.02 0.02 0.02 0.02

Propoxur 0.05 0.05 0.05 0.05

Pyrethrin I 1 1 1 1

Tefluthrin 0.05 0.05 0.05 0.05

Tolclofos-methyl 1 1 0.05 1

Warfarin NS NS NS NS

NS means MRL has not been established.

a According to Codex Alimentarius Commission (FAO/WHO, 2004) and Council Dir

3. Results

The method was validated under the optimized conditions bydetermining the limits of detection (LOD) and quantitation (LOQ),the recovery and precision at different levels of the fortification.The recovery values ranged from 81% to 115%, and precisionranged from 2% to 12% for all fresh vegetables. For the analysisof pesticide residues at the ng/g or mg/g levels, accuracy andrecovery of 70–120% considered acceptable (Herdman et al.,1988; Pose-Juan et al., 2006; Gonzalez-Rodrıguez et al., 2008a,2008b; Berrada et al., 2010; Gilbert-Lopez et al., 2010) and fulfillthe criteria for quantitive methods (SANCO, 2003). Limits of LODand LOQ were calculated to be the concentrations of pesticideresulting in a signal-to-noise ratio of 3 and 10, respectively. TheLODs (0.002–0.010 mg/kg) and LOQs (0.006–0.020 mg/kg) for thetested pesticides were much lower than the maximum residuelevels (MRLs), allowed for vegetables in Saudi Arabia demonstrat-ing that GC–MS at its operation conditions was sensitive to theanalytes (Araoud et al., 2007). Residue samples that were consid-ered to be non-detections were assigned a value of zero.

Data in Table 2 show the maximum residue limits (MRLs) ofthe selected pesticides in different vegetables. No MRL is yetestablished for azobenzene, bioallthrin, biphenyl, ENT 92,ethiofencarb, heptenophos, and warfarin.

The occurrence and distribution of pesticides in four major bigsupermarkets located in Al-Qassim region (West of KSA) was themain aim of this work. The reason for investigations in this regionis Al-Qassim region is one of the largest agricultural areas in KSAand produces the majority of vegetables consumed locally.Therefore, controlling the pesticide levels seems to be a sub-stantial contemporary public health problem to grantee foodquality and to evaluate alimentary risk. Table 3 shows that a totalof 40 samples consisting of different commodities and collectedfrom supermarket number 1 that were analyzed for 12 pesticidesfrom different chemical groups. Among the different pesticidesin vegetables, the insecticide ethiofencarb was found with the

plant Green pepper Lettuce Carrot Cabbage

0.01 0.01 0.01 0.01

NS NS NS NS

NS NS NS NS

NS NS NS NS

0.05 0.05 0.05 0.05

0.05 0.05 0.05 0.05

0.02 0.02 0.02 0.02

0.05 0.05 0.10 1

0.02 0.02 0.02 0.02

0.01 0.01 0. 01 0.01

NS NS NS NS

NS NS NS NS

NS NS NS NS

0.01 0.01 0.01 0.01

0.10 0.50 0.50 0.50

0.5 2 0.01 0.05

1 1 1 1

0.02 0.02 0.02 0.02

0.05 0.05 0.05 0.05

1 1 1 1

0.05 0.05 0.05 0.05

1 2 0.5 0.50

NS NS NS NS

ective (2003).

Table 3Levels (mg/kg) of residues in different vegetables collected from supermarkets no 1 located in Al-Qassim region.

Pesticide Pesticide level, mg/kg

Tomato Squash Cucumber Egg-plant Green pepper Lettuce Carrot Cabbage

Azobenzene 0.13170.03 0.11770.04 0.00470.001 – – – 0.07270.02 0.85170.14

Biphenyl – 0.04070.02 – – – 2.91770.10 – –

Bromoxynil – – – – – – – 2.29270.42a

Carbaryl – 0.23770.05a 0.38470.08a 1.91770.21a 2.22870.24a 1.64170.30a 0.06970.02a

Carbofuran – 0.19470.06a – 0.48470.08a – – – –

Chlorpyrifos – – – – – – – 6.20770.85a

Dicofol – – – – – – – 0.14770.05a

Ethiofencarb – – – – – 7.64870.88 – –

Methoxychlor – – – – – – – 0.24470.06

Paraquat – – – – – – – 0.38270.06a

Tolclofos-methyl 7.31270.52a – – – – – – –

Warfarin – – – – – – – 0.14770.03

SMean level 7.443 0.588 0.388 2.401 2.228 12.206 0.072 10.339

Each value is the mean of five samples with six determinations.

a Exceed the MRL.

Table 4Levels (mg/kg) of residues in different vegetables collected from supermarkets no 2 located in Al-Qassim region.

Pesticide Pesticide level, mg/kg

Tomato Squash Cucumber Egg-plant Green pepper Lettuce Carrot Cabbage

Azobenzene 0.13170.01 – – – – – – –

Bioallethrin – – – – 1.08970.12 – – –

Biphenyl – – 0.36270.10 0.59770.11 0.50070.08 – 0.36070.07 –

Carbaryl 0.39070.04 1.14870.21a 0.82670.11a 1.68670.19a 0.65370.21a 0.53870.13a 0.89170.24a 1.76570.18a

Carbofuran – – – 1.52870.09a 0.65470.10a 0.40170.05a 1.61670.20a

Dicofol 0.0570.01 – – – – – – –

Dieldirn – – 0.02270.009a – – – – –

Heptenophos – – – – – – 3.26770.18 –

Lindane 0.34270.10a – – – – – – –

Malathion – – – – 0.04570.01 – – –

Metalaxyl – – 0.32570.08a – – – – –

Propoxur – – – – 0.57770.10a – 0.61370.11a 1.17570.25a

Pyrethrin I – – 0.45470.06 – – – – –

Tolclofos-methyl 2.43570.06a 1.69670.09a – – – – – –

Warfarin – – 0.89670.17 – – – – –

SMean level 3.348 2.844 2.885 3.811 3.518 0.939 6.747 2.940

Each value is the mean of five samples with six determinations.

a Exceed the MRL.

K.A. Osman et al. / Ecotoxicology and Environmental Safety 73 (2010) 1433–14391436

highest concentration of 7.648 mg/kg in lettuce, followed by thefungicide tolclofos-methyl with concentration of 7.312 mg/kg intomato. Tolclofos-methyl was found to exceed the MRL in tomato.The results also showed that carbaryl was found in squash,cucumber, egg-plant, green pepper, lettuce and cabbage andexceeded the MRL in these commodities. Eight pesticide residueswere detected in cabbage and five of them exceeded the MRLs.The sum of mean levels of the 12 pesticides illustrate that lettucefollowed by cabbage and then tomato contained the highestconcentrations with values of 12.206, 10.339 and 7.433 mg/kg,respectively.

The levels of 15 pesticides in vegetables collected fromsupermarket number 2 are illustrated in Table 4. Heptenophoswas the insecticide with the highest concentration of 3.267 mg/kgin carrot, followed by the fungicide tolclofos-methyl withconcentration of 2.435 and 1.696 mg/kg in tomato and squash,respectively. Tolclofos-methyl was found to exceed the MRLs intomato and squash. The results also showed that carbaryl wasfound in all the tested commodities and exceeded the MRL in allthe tested commodities except tomato. Carbofuran exceededthe MRLs in egg-plant, green pepper, lettuce and carrot, whilepropoxur exceeded the MRLs in green pepper, carrot and cabbage.

Also, dieldrin was exceeded the MRL in cucumber with meanlevel of 0.022 mg/kg. The sum of mean levels of the 15 pesticidesillustrate that carrot followed by egg-plant, green pepper andtomato contained the highest concentrations of pesticide residueswith mean values of 6.747, 3.811, 3.518 and 3.348 mg/kg,respectively.

Data in Table 5 show that a total of 40 samples consisting ofdifferent commodities and collected from supermarket number 3that were analyzed for nine pesticides from different chemicalgroups. Among the different pesticides in vegetables, carbofuranand carbaryl had the highest concentrations of 1.573 and1.457 mg/kg in lettuce and cucumber, respectively. Carbofuranexceeded the MRLs in lettuce and carrot, while carbaryl exceededthe MRLs in cucumber and lettuce. Propoxur exceeded the MRLsin egg-plant, green pepper and carrot, while tefluthrin exceededthe MRLs in tomato. The results also showed that biphenyl wasfound in all the tested commodities except tomato. The sum ofmean levels of the nine pesticides illustrate that lettuce followedby cucumber contained the highest concentrations with values of3.086 and 2.022 mg/kg, respectively.

Data in Table 6 show that a total of 40 samples consisting ofdifferent commodities and collected from supermarket number 4

Table 5Levels (mg/kg) of residues in different vegetables collected from supermarkets no. 3 located in Al-Qassim region.

Pesticide Pesticide level, mg/kg

Tomato Squash Cucumber Egg-plant Green pepper Lettuce Carrot Cabbage

Biphenyl – 0.19670.05 0.30470.01 0.36370.06 0.32170.03 0.24870.08 0.22870.07 0.42970.10

Carbaryl – – 1.45770.18 – – 1.26570.19a – –

Carbofuran – – – – – 1.57370.23a 0.45570.17a –

ENT 92 – – – 0.33770.06 – – – –

Metalaxyl – – 0.26170.05 – – – – –

Paraquat 0.40670.05a

Propoxur – – – 0.80570.11a 0.55770.06a – 0.69870.03a –

Tefluthrin 0.08070.01a – – – – – – –

Tolclofos-methyl 0.24270.02 0.54470.05 – – – – – –

SMean level 0.250 0.74 2.022 1.505 0.878 3.086 1.381 0.835

Each value is the mean of five samples with six determinations.

a Exceed the MRL.

Table 6Levels (mg/kg) of residues in different vegetables collected from supermarkets no. 4 located in Al-Qassim region.

Pesticide Pesticide level, mg/kg

Tomato Squash Cucumber Egg-plant Green pepper Lettuce Carrot Cabbage

Amitrole – – – – 0.76870.18a – – 0.87270.10a

Bioallethrin – – – – 0.23870.07 – – –

Carbaryl – 0.20970.05a – – – – – 1.05770.11a

Carbofuran – 0.48870.04 – – – 0.67570.05a 0.95370.10a –

ENT 92 – – – – – – 0.58270.06 –

Metalaxyl – 1.04970.11a – – – – – –

Paraquat – – – – – – – 1.23470.15a

Propoxur – – – – 1.54470.15a 1.99970.23a –

Tolclofos-methyl – – 0.41970.08a – – – – 0.42770.07

SMean level – 1.746 0.419 – 2.550 0.675 3.534 3.590

Each value is the mean of five samples with six determinations.

a Exceed the MRL.

K.A. Osman et al. / Ecotoxicology and Environmental Safety 73 (2010) 1433–1439 1437

that were analyzed for nine pesticides from different chemicalgroups. Among the different pesticides in vegetables, propoxurwas the insecticide with the highest concentration of 1.999 and1.544 mg/kg in carrot and green pepper, respectively, andexceeded the MRL in these two commodities. Carbofuranexceeded the MRLs in squash, lettuce and carrot. Also, violatedMLRs were recorded with tolclofos-methyl (cucumber), carbaryl(squash and cabbage), amitrol (green pepper and cabbage),paraquat (cabbage) and metalaxyl (squash). However, none of thetested pesticides were detected in either tomato or egg-plant. Thesum of mean levels of the nine pesticides illustrate that cabbagefollowed by carrot contained the highest concentration of pesticideresidues with values of 3.590 and 3.534 mg/kg, respectively.

4. Discussion

A total of 160 vegetable samples cultivated under greenhouseconditions and collected from the four local supermarkets ofAl-Qassim region were analyzed. In the analyzed samples 23pesticides belonging to various chemical groups (aromatichydrocarbon, azobenzene, bipyridylium, carbamate, coumarinanticoagulant, hydroxybenzonitrile, natural pyrethrin, organo-chlorine, organophosphate, phenylamide, pyrethroid, thiocynateand triazole) with different physicochemical properties(13 insecticides, 3 fungicides, 3 herbicides, 2 acaricides, 1 rodenticideand 1 nematicide) were found (Tables 1 and 7). Frequency,concentration and identity of pesticides found in analyzedsamples are presented in Table 7. Out of 160 samples analyzed,

pesticide residues were not detected in 71 samples (44.40%),while 89 samples (55.60%) contained detectable amount ofpesticide residues. 53 out of 89 pesticide-contained samples(59.60%) were above the MRLs established by Codex AlimentariusCommission (FAO/WHO, 2004) and Council Directive (2003),while 36 samples (40.60%) contained pesticide residues eitherbelow the MRLs or not established. MRL values exceeded mostoften in cabbage (11 samples) followed by carrot, green pepperand squash (7 samples), cucumber and lettuce (6 samples),egg-plant (5 samples) and then tomato (4 samples). Cabbage getsdamage by many insects and pathogens such as Myzus persicae,Pieris rapae (L.), Plutella xylostella, Spodoptra exigua Hubner,Phyllotreta striolata Fabricius, bacterial soft rot, and downymildew (Du et al., 2002; Gu et al., 2004). Therefore differentpesticides are applied ineluctably to control pests of cabbage. Alsoin Al-Qassim region, the overuse of pesticides and randommixture of pesticides are serious problem in vegetablescultivated in greenhouses. In the present study, the highestconcentrations for the tested pesticides were recorded withinsecticide ethiofencarb (lettuce) followed by the fungicidetolclofos-methyl (tomato), the herbicide bromoxynil (cabbage),the acaricide azobenzene (cabbage), the nematicide carbofuran(carrot) and then rodenticide warfarin (cucumber). The residuallevels differed between the species of the treated vegetables, anddependent mostly on the time of harvest, size of fruits, mode ofpesticide application, etc. (Pose-Juan et al., 2006; Gonzalez-Rodr�ıguez et al., 2008b; Chen et al., 2010).

Carbaryl is most often exceeded MRL values (17 samples),followed by carbofuran (11 samples), propoxure (8 samples),

Table 7Frequencies and pesticide concentration ranges found in the tested samples.

Pesticide type Common name No. of positive samples Range (mg/kg) No of samples exceed MRL

Acaricide Azobenzene 6 0.004–0.851 NS

Dicofol 2 0.05–0.147 1

Fungicide Biphenyl 13 0.04–2.917 NS

Metalaxyl 3 0.261–1.049 2

Tolclofos-methyl 7 0.242–7.312 4

Herbicide Amitrole 2 0.768–0.872 2

Bromoxynil 1 ND–2.292 1

Paraquat 3 0.382–1.234 3

Insecticide Bioallethrin 2 0.238–1.089 NS

Carbaryl 18 0.069–2.228 17

Chlorpyrifos 1 ND–6.207 1

Dieldirn 1 ND–0.022 1

ENT 92 2 0.377–0.582 NS

Ethiofencarb 1 ND–7.648 1

Heptenophos 1 ND–3.267 NS

Malathion 1 ND–0.045 –

Methoxychlor 1 ND–0.244 –

Lindane 1 ND–0.342 1

Propoxur 8 0.557–1.999 8

Pyrethrin I 1 ND–0.454 –

Tefluthrin 1 ND–0.080 1

Nematicide Carbofuran 11 0.194–1.616 11

Rodenticide Warfarin 2 0.147–0.896 NS

NS means MRL has not been established.

K.A. Osman et al. / Ecotoxicology and Environmental Safety 73 (2010) 1433–14391438

tolclofos-methyl (4 samples), paraquat (3 samples), metalaxyl andamitrole (2 samples), lindane, dieldrin, chlorpyrifos, tefluthrin,bromoxynil and dicofol (1 sample). Also the data show thatcarbaryl was the most frequently pesticides suggesting that thispesticide was in common use in vegetable samples found inAl-Qassim region. The use of carbaryl in vegetables may be due toits relatively low toxicity (Tomlin, 2002).

In terms of pesticide residues some samples contained morethan one residue. The reason for that might be that vegetablescultivated under greenhouse conditions are highly sensitive topests and need for successive applications of pesticide treatments,leaving in consequence higher level of residues that tolerated(Gonzalez-Rodrıguez et al., 2008a, 2008b; Paulino de Pinho et al.,2010), and protected from rapid degradation by direct sunlight(Mansour et al., 2009). Overall, pesticides found in this study weresimilar to those found in other studies (Amoah et al., 2006; Cabrasand Conte, 2001; Dogheim et al., 2004; Gebara et al., 2005;Poulsen and Andersen, 2003; Gonzalez-Rodrıguez et al., 2008a),but 53 samples of 89 had residue levels 4MRL. In the presentstudy, the most irregularities were due to a poor compliance ofthe pre-harvest interval, especially after repeated treatments withsome active ingredients (Nasreddine and Parent-Massin, 2002;Rial-Otero et al., 2005).

5. Conclusion

The present study shows a high incidence rate of pesticideresidues (mostly insecticides) in vegetables cultivated undergreenhouse conditions and the most critical commodity iscabbage followed by carrot. The contamination levels of pesticideresidues could be considered a possible public health problembecause most of the tested vegetables except squash are usedwithout cooking treatment and used in salad dishes. Also,vegetables consumers could be exposed to more than onepesticide at the same time from the same or different chemicalgroups. The most disturbing findings was that residue of somepesticides which prohibited and not approved for use on aparticular vegetables such as lindane, methoxychlor, ENT 92,paraquat, azobenzene were found in some vegetable samples.

On the basis of the above findings, the results recommend theneed for regular monitoring of a greater number of samples forlong periods for pesticide residues, especially those cultivatedunder greenhouse conditions. A future study in a longer period oftime would allow obtaining a deeper knowledge about thefulfillment of vegetables produced in Al-Qassim region to SaudiArabia regulations with respect to the use of pesticides and theirpresence in these vegetables. This study has provided importantinformation on pesticide residues contamination on vegetablesfrom Al-Qassim region for the first time.

Acknowledgment

The authors wish to thank the Dean of Scientific Research,Al-Qassim University, Saudi Arabia for the financial support of thepresent work.

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