Field Incurred Endosulfan Residues in Fresh and Processed Vegetables and Dietary Intake Assessment

Abstract

Mitigation in endosulfan residues was determined in spinach, cauliflower, potato, brinjal, tomato, and okra by using different techniques. The endosulfan residues were determined in 66 samples of different vegetables, and it was found that the highest endosulfan residues (mg kg⁻¹) were at the raw stage in okra (1.71), brinjal (1.50), and spinach (1.16), respectively. The residue of endosulfan was lowest in potato (0.130) mg kg⁻¹. Washing reduced the endosulfan residue from 15 to 28%, peeling reduced it from 60 to 67%, and cooking further lowered it from 18 to 31% in all vegetables. Dietary intake assessment revealed that only samples of okra exceeded the maximum permissible intake value at the raw stage, whereas all the other samples were below maximum permissible intake value, although some were exceeding the maximum residue limits at the raw stage.

Keywords:

• Endosulfan
• Farmer field
• Vegetables
• Household processing
• Dietary intake assessment

INTRODUCTION

Vegetables are an indispensable component of our everyday food due to their nutritional value.[1] Vegetables are a rich source of antioxidants and total phenols. The vegetables grown in subtropical climatic conditions are threatened by the proliferation of insects, which results in massive losses in yield. Hence, the use of plant protection products like insecticides has made the business more profitable in terms of greater harvests and improved crop quality. However, pesticides are toxic chemicals used in preventing or mitigating the crop pests like insects, weeds, rodents, etc.[2]

Endosulfan is a chlorinated hydrocarbon insecticide containing a sulphite group and is marketed as a mixture of two isomers having the same insecticidal ability. It is highly persistent, practically insoluble in water, non-volatile, and stable. At least 6 weeks should lapse between its last application and harvesting of food crops. Acute oral LD₅₀ for rat is 80–110 mg kg⁻¹.[3] Endosulfan is a highly toxic pesticide in the Environmental Protection Agency (EPA) toxicity class I and is a suspected endocrine disrupter.[3] Chronic poisoning resulting from food residues causes kidney and liver damage.

Previous studies illustrate that endosulfan is the most commonly occurring insecticide in vegetables.[4–6] Insecticide residues from vegetables can be removed by household processing like washing, peeling, and cooking.[7–9] Randhawa et al.,[7] during working on endosulfan residues in supervised field trials, found higher residues of endosulfan than the maximum residue limits (MRLs) in some vegetables of the winter and summer seasons. The results suggested that endosulfan residues decreased with household processing operations; however, the sample size was too small to calculate dietary risk assessment. These studies are of little practical use to the consumer who wants to know what effect household preparation has upon the field incurred residues of endosulfan in vegetables. This article describes the dietary intake/risk assessment of endosulfan residues from vegetable samples procured directly from the farmer's field. Furthermore, effect of household processing on field incurred endosulfan residues will also be taken into account.

MATERIALS AND METHODS

Vegetable Sampling from the Farmer's Field

The growers[10–12] of both winter vegetables—spinach (Spinacia oleracea L.), cauliflower (Brassica oleracea L.), and potato (Solanum tuberosum L.) and summer vegetables—brinjal/egg plant (Solanum melongena L.), tomato (Lycopersicon esculentum L.), and okra (Abelmoschus esculentus L.), near the city of Faisalabad, Pakistan were selected in each season. They were allowed to grow these vegetables with their normal routine practices. The endosulfan insecticide was used by growers as their usual requirement. At the time of harvest, all of the vegetable samples (3 kg) were collected from the field, brought to laboratory, and analyzed on the same day or if necessary stored at −18°C after necessary processing as given below till analysis.

Processing of Vegetables, Extraction, and Determination of Endosulfan Residues

The vegetable samples were cleaned with a paper towel to remove soil contamination, then they were washed by placing them in a plastic tub and rinsing under normal tap water for 30 s with gentle rotation by hand and again dried with a paper towel. One portion was analyzed as such. The eggplant and potato were subjected to peeling and divided into two lots: one for analysis and the other one for further processing. The rest of the vegetables, potato and eggplant, were further sliced and cooked by placing 3/4 cup of water in the saucepan and adding 1/2 teaspoon of salt. The water was brought to a boil and 50 g of vegetable was added immediately. The vegetable was covered and cooked for 10–12 min and the contents were analyzed for endusulfan residues.[7] Endosulfan residues were extracted from raw and processed vegetables and determined by HPLC as given in Randhawa et al.[8]

Dietary Intake Assessment

The dietary intake assessment of endosulfan residues was determined by first calculating the maximum permissible intake (MPI) of endosulfan through the consumption of vegetables. The prescribed acceptable daily intake (ADI) of endosulfan is 0.006 mg/kg body weight/day[10] and weight of an average Pakistani adult is 64 kg.[11] By multiplying the upper limits of ADI with the body weight of an average adult, the MPIs were found to be 0.384 mg/person/day. Then, the values of dietary exposure were calculated by multiplying the residue levels with average per capita daily consumption (134 g) of vegetables.[12]

Statistical Analysis

Three parameters were used to report residue levels: range, mean value, and standard deviation at each sampling point, expressed as mg kg⁻¹. The data was analyzed through one way ANOVA. Mean values and standard deviations were calculated and analyzed by Minitab Software Package Version 14.0 (Minitab Inc., State College, PA, USA).

RESULTS AND DISCUSSION

Endosulfan recovery (mean of five replicates) in vegetables was as follows: spinach, 103 ± 2.5%; cauliflower, 95 ± 1.2%; potato, 98 ± 0.68%; eggplant, 92 ± 4.5%; tomato, 101 ± 2.8%; and okra, 100 ± 0.25%. The method used was pre-validated in our previous findings and given in Randhawa et al.[8] The results of endosulfan residue detected in vegetable samples collected from the farmer's field are presented in Table 1. The results indicated that at the raw stage the highest endosulfan residue was found in okra (0.691 to 3.10 mg kg⁻¹) followed by brinjal (0.087 to 2.81 mg kg⁻¹) and spinach (0.061 to 2.31 mg kg⁻¹). The residues were relatively low in potato samples (0.068 to 0.185 mg kg⁻¹) and were lower than the maximum residue limits (MRLs) specified by USEPA.[13] The endosulfan residues were lower in potato as compared to other vegetables because it is a tuber and there is no direct spray on the potato. The vegetables from the farmer's field further delineated that at the raw stage all the spinach samples contained endosulfan residue but one sample out of 10 exceeded MRLs. In the case of cauliflower, 2 out of 11, brinjal, 4 out of 12, tomato, 3 out of 11, and okra, 3 out of 12 samples exceeded MRLs. The frequent use of the pesticide in the field, especially prior to harvest, significantly (P < 0.05) contributes toward higher residues.[14]

Table 1  Endosulfan residues (mg kg⁻¹) in vegetables of farmers fields

	Raw			Washed			Peeled			Cooked
Vegetables	Range	Mean	Positive samples (%)	Range	Mean	Positive samples (%)	Range	Mean	Positive samples (%)	Range	Mean	Positive samples (%)
Spinach (n = 10)	0.061–2.31	1.16	10	0.048–1.61	0.845	0	NA	NA	NA	0.035–1.22	0.594	0
		(0.628)			(0.397)						(0.293)
Cauliflower (n = 11)	0.119–0.628	0.329	20	0.076–0.509	0.236	0	NA	NA	NA	0.055–0.315	0.163	0
		(0.152)			(0.119)						(0.079)
Potato (n = 10)	0.068–0.185	0.131	0	0.056–0.145	0.102	0	0.013–0.114	0.041	0	0.013–0.114	0.033	0
		(0.044)			(0.031)			(0.028)			(0.025)
Brinjal (n = 12)	0.087–2.81	1.50	33.33	0.068–2.46	1.27	16.16	0.052–0.706	0.412	0	0.052–0.706	0.339	0
		(0.822)			(0.728)			(0.198)			(0.164)
Tomato (n = 11)	0.073–0.779	0.388	30	0.063–0.554	0.285	20	NA	NA	NA	0.046–0.508	0.216	0
		(0.218)			(0.163)						(0.136)
Okra (n = 12)	0.691–3.10	1.71	27.27	0.479–2.38	1.33	9.09	NA	NA	NA	0.267–1.67	0.928	0
		(0.680)			(0.534)						(0.398)
NA means peeling was not done. Values in parentheses indicate standard deviation.

The findings revealed that washing showed a significant (P < 0.05) effect on the declining of endosulfan residue in different vegetables. The results (Table 1) indicated that after washing the highest mean endosulfan residue (mg kg⁻¹) was found in okra (1.33) followed by brinjal (1.27) and spinach (0.845), while the lowest residues were found in potato samples (0.102 mg kg⁻¹). The percent reduction of endosulfan residue after washing of vegetable samples is shown in Fig. 1. The vegetables from the farmer's field further delineated that after washing all the spinach and brinjal samples contained endosulfan residues. In the case of brinjal, 2 out of 12, tomato, 2 out of 11, and okra, 1 out of 12 samples exceeded MRLs (Table 1). The process of washing decreased endosulfan residue 28% in cauliflower, 27% in spinach, 26% in tomato, and 15% in brinjal. A significant (P < 0.05) reduction (15 to 28%) in endosulfan residue was observed during washing of the vegetables. Pesticide residues were partially removed by the washing operation and the results from the current study are consistent with earlier findings, which showed that residues of six pesticides on olives decreased after washing.[15]

Figure 1 Percent reduction of endosulfan residues in vegetables. (Color figure available online.)

The results indicated that the peeling significantly reduced the endosulfan residues from vegetables. The mean residues of endosulfan in potato and brinjal after peeling were 0.041 and 0.412 mg kg⁻¹, respectively (Table 1). All the brinjal samples were contaminated with endosulfan residues after washing but the process of peeling decreased endosulfan residue below MRL. Peeling decreased endosulfan residue 60 and 67% in brinjal and potato, respectively. The data clearly indicated that the peeling process had a significant (P < 0.05) effect on the removal of endosulfan residue and it confirms the presence of endosulfan residue in the skin of potato and brinjal. Thus, by removing the peel, greater amounts of pesticide residue were removed. These results are consistent with those reported in previous studies in potatoes with the nonsystemic phenylcarbamate insecticide chlorpropham, where the amount of residue removed by peeling was >90%.[16]

The results of endosulfan residue percentage detected in vegetable samples after cooking are presented in Table 1. The results indicated that after cooking the highest mean endosulfan residue was found in okra (0.928 mg kg⁻¹) followed by spinach (0.594 mg kg⁻¹) and brinjal (0.339 mg kg⁻¹), while the lowest residues were found in potato samples (0.033 mg kg⁻¹). The effect of cooking was higher on cauliflower followed by okra and spinach. The endosulfan residue decreased by 31% in cauliflower and 30% in okra. The least effect of cooking was found in the case of brinjal and potato by 17 and 19%, respectively. The results also showed that the heat treatment during cooking had a significant (P < 0.05) effect on decomposition of the pesticides in all the tested vegetable samples. The decrease ranged from 18 to 31% (Fig. 1). Overall, the present results agree fairly with those obtained by Yadav and Dashad,[17] Ramesh and Balasubramanian,[4] and Randhawa et al.[8] They reported that home cooking removed most of the pesticide residues from the produce.

The results of endosulfan residues dietary intake assessment in cooked vegetables are presented in Table 2. The results indicated that although one spinach sample exceeded the MRLs limit, dietary intake assessment revealed that the sample was well below the MPI value of 0.384 mg/person/day. The maximum dietary intake assessment indicated that the maximum residue taken by a person was with spinach (0.163 mg/person/day) after cooking. In cauliflower, 2 samples out of 11 were above the MRLs values but the dietary intake assessment indicated that they were well below the safe limit. Similarly, in brinjal and tomato, 4 and 3 samples exceeded MRLs values, but the result of dietary intake assessment showed that they are not injurious to health. In the case of okra, 3 samples out of 12 exceeded the MRLs, but the dietary intake assessment showed that out of 3, only 1 sample exceeded MPI limit and was alarming to the health of the masses. The dietary intake assessment result showed that most of the samples were well below the MPI limit and out the samples that exceeded MPI limit, the process of washing, peeling, and cooking cut down the pesticide residues to well below the MPI limit.

Table 2  Dietary intake assessment of endosulfan residues (mg/person/day) in vegetable samples after processing (cooking)

	MPI (%)		Cooked
Vegetables	Range	Mean	Range	Mean
Spinach (n = 10)	1.30–42.44	20.83	0.005–0.163	0.080
Cauliflower (n = 11)	1.82–10.93	5.72	0.007–0.042	0.022
Potato (n = 10)	0.52–3.90	1.04	0.002–0.015	0.004
Brinjal (n = 12)	1.82–24.73	11.71	0.007–0.095	0.045
Tomato (n = 11)	1.56–17.70	7.55	0.006–0.068	0.029
Okra (n = 12)	9.37–58.33	32.29	0.036–0.224	0.124

CONCLUSION

Pesticides are essential in vegetable production and their side effects must be weighed in comparison to boosting crop yield and ensuring availability of crops for consumption of mankind. But, there is a need to educate the farmer about the judicious use of pesticides. Although higher residue of endosulfan was observed in some vegetables, their levels dropped below MRL values by food processing like washing, peeling, and cooking. The result of dietary intake assessment reveled that almost all of the samples were well below the safe limit even though some exceeded the MRLs values.