Removal of Trace Pesticide Residues from Produce

AC003 (10/00)

Removal of Trace Pesticide Residues from Produce

By Dr. Walter J. Krol

Department of Analytical Chemistry

The Connecticut Agricultural Experiment Station

123 Huntington Street

P.O. Box 1106

New Haven, CT 06504-1106

Telephone: (203) 974-8456 Fax: (203) 974-8502

E-mail: Walter.Krol@ct.gov

Background

The Department of Analytical Chemistry at the Connecticut Agricultural Experiment Station (CAES) has established a program in conjunction the Department of Consumer Protection (DCP) to examine fruits and vegetables sold in the state for pesticide residues. The primary goal of this program is to determine if the amounts and types of pesticides found on fruits and vegetables are in accordance with the tolerances set by the EPA. Violations of the law occur when pesticides are not used in accordance with label registration and are applied in excessive amounts, or when pesticides are applied to crops on which they are not allowed

Over the past ten years more residues have consistently been found on raw produce than on the corresponding processed commodities. This led to the hypothesis that certain types of processing or household preparation may serve to reduce pesticide residues. Hypothesizing that rinsing during the processing procedure may play some role in reducing residue levels, we initiated a study to examine the effects that rinsing produce under tap water has upon pesticide residue levels. The results of this study are presented below.

Numerous fruit and vegetable wash products recently appeared in the marketplace. Four fruit and vegetable wash products, FIT®, Fruit & Vegetable WashÔ , OrganicleanÔ , and Vegi-CleanÔ , were compared to a one-percent Palmolive® solution and to rinsing alone to gauge the effectiveness of these products at removing pesticide residues from produce. These results are also presented.

Rinsing with Tap Water

Although it has been assumed for many years that rinsing fruits and vegetable prior to consumption reduces the amounts of pesticide residues, this anecdotal approach needed laboratory confirmation. There are numerous studies in the scientific literature that have examined the effect of washing produce to remove pesticide residues as a step in commercial crop processing. These studies are of little practical use to the consumer who wants to know what effect household preparation has upon reducing pesticide residue levels. There are also a handful of studies that examine the effects of washing as part of larger household preparation studies. In most cases, however the sample sizes were too small to apply statistical analysis (1).

In 1997 we initiated a research program whose objective was to examine the effect that the simple household technique of rinsing with tap water would have upon reducing pesticide residues in produce. A wide variety of crops that contained residues were examined.

Residues of DDE, a metabolite of DDT, were also studied. Although many persistent organohalogen pesticides (POPs), such as DDT, were banned for use on food crops between 1972 and 1978 in the United States, they have remained in the environment where they continue to be incorporated into plant biomass (1).

Data presented in this study show that a short rinse in tap water reduces pesticide residues on many types of produce (Table 1). Residues of vinclozolin, bifenthrin and chlorpyrifos were not reduced. This study also shows that the water solubility of pesticides does not play a significant role in the observed decrease. The majority of pesticide residue appears to reside on the surface of produce where it is removed by the mechanical action of rinsing (1).

Table 1. Results of tap water rinsing in reducing residues across all commodities.

Pesticides Pairs of Data Significantly Reduced Water Solubility (mg/L @ 20 ° C) Insecticides Endosulfan 60 Yes 0.32 Permethrin 37 Yes 0.2 Diazinon 22 Yes 40 DDE 21 Yes <1 Chlorpyrifos 13 No 2 Methoxychlor 12 Yes 0.1 Malathion 7 Yes 130 Bifenthrin 7 No 0.1 Fungicides Captan 34 Yes 3.3 Vinclozolin 23 No 3.4 Iprodione 13 Yes 13 Chlorothalonil 9 Yes 0.6

Fruit and Vegetable Wash Rinsing

In the Spring and Summer of 2000, the effectiveness of four commercially available fruit and vegetable wash products at removing pesticide residues from produce was compared to a 1% solution of Palmolive® and to rinsing with tap water alone. The nine pesticides examined in this study included many of those from our previous study. The three fungicides chlorothalonil, iprodione, and vinclozolin were examined as was the herbicide DCNA, and the insecticides bifenthrin, diazinon, endosulfan, malathion and permethrin.

A total of twenty-eight harvests were made including sixteen of lettuce, four of strawberry, four of tomatoes, and four control lettuce batches. Each batch was divided into seven treatment groups. One group was analyzed in an unrinsed state as received from the field; one group was rinsed under tap water for one minute. The five remaining groups were individually treated with either FIT®, Fruit & Vegetable WashÔ , OrganicleanÔ , Vegi-CleanÔ , or a 1% solution of Palmolive® and then rinsed under tap water for one minute. In the case of the control lettuce batches all seven-treatment groups were processed in an unrinsed state to ensure that each group contained statistically equivalent pesticide residue levels.

A total of 196 samples were processed. Detailed statistical analysis showed that in all cases at least one group was different from the rest. Pairwise comparison showed that the group that was different was the unrinsed produce. There is little or no difference between tap water rinsing or using a fruit and vegetable wash in reducing residues of the nine pesticides studied. The removal of waxes and/or dirt from the produce was not examined as part of this study.

Suggestions

Data from our annual market basket survey (2) continue to show that residues of pesticides on fruits and vegetables in Connecticut are generally well within the tolerances set by the EPA. To minimize the dietary intake of pesticide residues on food we suggest that the consumer take the following steps based upon our studies to date.

At a minimum rinse all fresh produce under tap water for at least thirty seconds.

The mechanical action of rubbing the produce under tap water is likely responsible for removing pesticide residues. Mild detergents or fruit and vegetable washes do not enhance the removal of pesticide residues from produce above that of rinsing with tap water alone.

References

1. W.J. Krol, T.L. Arsenault, H.M. Pylypiw, M.J.I. Mattina. J. Argic. Food Chem. 2000, 48, 4666-4670.

2. W.J. Krol, T.L. Arsenault, M.J.I. Mattina "Pesticide Residues in Food Sold in Connecticut 1999"; Connecticut Agricultural Experiment Station Bulletin 964, April, 2000.

Summary

A three-year study showed that rinsing under tap water significantly reduced residues of nine of the twelve pesticides examined across fourteen commodities. Four fruit and vegetable wash products were found to be no more effective at removing eight of nine pesticide residues from produce than either a 1% solution of dishwashing liquid or rinsing under tap water alone for three commodities studied.