The variation of pesticide residues in fruits and vegetables and the associated assessment of risk

High levels of triazophos residues detected in carrots during routine monit oring led to the discovery of a wide variability between levels in individu al roots, Conventional point estimates of consumer exposure were carried ou t. Due to the assumptions used, these calculations were likely to give rise to gross overestimates. In 1997, data were obtained for individual apples, pears, peaches, nectarines, oranges, bananas, and tomatoes that showed sim ilar levels of variability in a range of organophosphate and carbamate resi dues. Point estimate models that had previously been used for intake estima tes for carrots were not appropriate since it was necessary to take account of not only the variation of residue levels from crop item to crop item bu t also the variation in eating patterns in individual consumers. Probabilis tic modeling was identified as a suitable way to produce multifactorial sub models and address some of the problems of combining distributions of consu mption and residues. Consumption data from 1675 toddlers were linked with r esidue distributions from individual crop items not only to allow combinati ons of fruit consumed but also to allow for the variability in residue leve ls that occur between individual crop items. The model was also capable? of taking account of the percentages of crops that did not contain any detect able residues; this information was available from initial screens of bulke d samples and percentage of crop not treated in the case of carrots. The ou tputs from the models were given as percentages of consumers that could exc eed a toxicological end point; this could be the acute reference dose or a factor of the no-observable-adverse-effect level. Modeling in this way was considered to give a realistic view of the likely short-term exposure and t he output was used as an aid to decision malting in terms of necessary regu latory action. Background. As a result of high levels of triazophos detected in carrots du ring routine monitoring, studies were carried out to determine the variabil ity of organophosphate residue levels in individual roots. Results obtained indicated that the highest residue levels could be 25 times the mean level in bulked samples (which were used in routine monitoring). Since sufficien t levels of organophosphate compounds can give rise to toxicological effect s after a single exposure, it was considered necessary to carry out assessm ents of short-term or acute consumer risk. At that time, models available w orldwide were designed only to carry out point estimates of long-term expos ure. From consumption data, it was possible to derive the levels of carrot consumption during a single day and calculations were carried out assuming all carrots contained the highest levels of residues found in trials. This led to a gross overestimate of likely exposure but was considered to give t o intakes that eroded margins of safety; these were not a cause for extreme regulatory action. Further studies were carried out on other crops that ma y be eaten whole, at one sitting, and without processing to consider whethe r the large variability of organophosphate residues was a phenomenon that w as common to other fruits and vegetables.