Occurrence and risks associated with chlormequat residues in a range of foodstuffs in the UK.

Trends in the usage pattern of chlormequat (a plant growth regulator) on cereal crops in the UK over the past 6 years are presented. The figures have been supplemented by monitoring of chlormequat residues in food commodities through the UK surveillance programme, and for cereals, the carry-through into a number of processed cereal-based foods has been followed. A downward trend of chlormequat residue levels in pears sampled between 1997 and 2002 was observed. This decline reflects changes that were introduced in European and national regulations and which have proven to be extremely effective in reducing both the frequency of detection and levels of chlormequat residues. Both acute and chronic risk assessments were undertaken based on aggregate dietary exposure data. Even when the highest residues observed were used in the calculations, the assessments showed that both the short- and long-term intakes for all consumer groups would be unlikely to cause adverse health effects and were therefore not of any cause for concern.

An example to illustrate the potential use of probabilistic modelling to estimate operator exposure to pesticides.

To illustrate the potential for probabilistic simulation modelling of operator exposure a probabilistic model was constructed using the draft EUROPOEM II database. The model also incorporated actual pesticide use data. Although the EUROPOEM II database is not complete, and the resulting simulation has to be regarded as only provisional, the data were sufficient to illustrate some of the principles involved. The model was constructed using non-parametric empirical input distributions. Associations were observed in the input exposure data and were reflected in the model. The exposure and usage data were all variable and showed highly negatively skewed distributions and the technique avoided concerns about having to define single representative values for point estimates. Increasing the number of iterations improved the stability of the output, but as expected, resulted in higher exposures being predicted due to a combination of rare events. Analysis of the inputs for individual iterations giving high results indicated that, in this example, these were due to unrepresentatively high input values for inhalation exposure. Simulations that excluded these values were more stable and showed lower exposures, illustrating the need to ensure the validity of the input distributions.

The need for appropriate use information to refine pesticide user exposure assessments.

Risk assessment compares hazard information with an exposure assessment (Report of the OECD workshop, 1995). To characterise the risk data on the level, duration and frequency of exposure are required. This paper illustrates how, in the absence of specific usage data, structural and other data may be used to provide some estimates of daily work rates. The usefulness of detailed pesticide usage data to refine the exposure assessment is also shown. Scientifically sound usage data are required, and to ensure a harmonised approach requires guidelines. The current OECD guidelines for the collection of usage statistics (Thomas for the Eurostat Pesticides Statistics Taskforce, 1999) are designed to collect usage data for environmental reasons, but are a good basis. The adaptation of the OECD guidelines to collect information for user exposure assessments is discussed.

A practical application of probabilistic modelling in assessment of dietary exposure of fruit consumers to pesticide residues.

In 1996, studies on a range of organophosphate and carbamate pesticide residues in fruit that may be eaten as single items reported variability. The usual point estimate exposure model did not take account of the variation in residue levels between items or variation in consumption patterns of individual consumers. Using only the highest residue levels and consumption values for each of the multiple sources (different fruit) could lead to overestimates of residue intakes which would indicate higher than actual levels of risk. Probabilistic simulation was identified as a tool that could utilize all the available information from the variability studies and fruit consumption data collected from dietary surveys. The estimation of exposure of toddlers to carbaryl is shown as an example. The number of samples representing some combinations of fruit in the toddler dietary survey was particularly low and the validity of extrapolating from these was unknown. Therefore, consumption values were simulated using the data for frequency and amount eaten from the whole database. The data indicated that there were some weak positive associations between consumption levels of the different fruit. However, inclusion of correlated sampling in the model simulation was considered too conservative. The profiles of carbaryl residues in different retail batches differed. Therefore a model was constructed that differentiated between different residue profiles and sampled separate residue levels for each item assumed to be eaten. Two simpler models, both ignoring the effect of re-sampling from the same batch, were also used to estimate exposure. All three models were considered to give realistic views of the likely short-term intakes and the outputs were useful as an aid to decision-making in terms of necessary regulatory action.

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

UNLABELLED: High levels of triazophos residues detected in carrots during routine monitoring led to the discovery of a wide variability between levels in individual roots. Conventional point estimates of consumer exposure were carried out. 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 similar levels of variability in a range of organophosphate and carbamate residues. Point estimate models that had previously been used for intake estimates 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 but also the variation in eating patterns in individual consumers. Probabilistic modeling was identified as a suitable way to produce multifactorial submodels and address some of the problems of combining distributions of consumption and residues. Consumption data from 1675 toddlers were linked with residue distributions from individual crop items not only to allow combinations of fruit consumed but also to allow for the variability in residue levels that occur between individual crop items. The model was also capable of taking account of the percentages of crops that did not contain any detectable residues; this information was available from initial screens of bulked samples and percentage of crop not treated in the case of carrots. The outputs from the models were given as percentages of consumers that could exceed 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 the output was used as an aid to decision making in terms of necessary regulatory action. BACKGROUND: As a result of high levels of triazophos detected in carrots during routine monitoring, studies were carried out to determine the variability 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 sufficient levels of organophosphate compounds can give rise to toxicological effects after a single exposure, it was considered necessary to carry out assessments of short-term or acute consumer risk. At that time, models available worldwide were designed only to carry out point estimates of long-term exposure. 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 to intakes that eroded margins of safety; these were not a cause for extreme regulatory action. Further studies were carried out on other crops that may be eaten whole, at one sitting, and without processing to consider whether the large variability of organophosphate residues was a phenomenon that was common to other fruits and vegetables.