| With the increasing population of the world, all government are facing the problem with how to solve food supply and food safety properly, and therein pesticide has been playing an important role in protecting crop and enhancing yield, however, all people concern pesticides residue in food and their toxicity. There are hundreds of pesticides, such as phosphate pesticide, chlorinated pesticide, etc. As a major food exporting country, China is frequently facing technical trade barrier with pesticide residues set up by some importing countries during international trade, therefore, based on scientific data, developing dietary exposure assessment for pesticides residues under general guideline to total exposure assessment and evaluating health risk from pesticides residue will provide powerful scientific basis for management department to take more effective measures in order to break down technical trade barrier from importing countries and protect domestic consumer benefit. This study does have important academic value and practical benefits.This study builds exposure assessment model for pesticides residue in food based on data from national pollutant monitoring network in 2000-2006, monitoring data for pesticides residue in export food in 2005-2006, monitoring data for pesticides residue in frozen spinach exported from Shandong Province to Japan in 2005, the data of national dietary survey in 2002. This model includes point estimation and probabilistic assessment model, etc. and this model is built on data available and analysis on variability and uncertainty. This paper takes chlorpyriofos as example to study exposure risk of chlorpyriofos in Chinese dietary structure, difference between point estimation and probabilistic assessment of pesticides residue in diet, difference of exposure assessment for cholorpyriofos residue in export vegetable and domestic market and analysis methods for variability and uncertainty by probabilistic assessment. Most important achievement as below:â… . Based on research on analysis method about pesticide residue in food and statistical analysis on pesticide residue data in food, conclusions are drawn as the following:1. The detection process for anilazine GC-MS has been established, which proves that multiple residual detection method of high flux for pesticide is as important as its validation method. The process has good performance in linear relationship, the range of recovery rate and detection limit can meet standard from anilazine detection method for import and export food in China2. The positive rate of pesticide is higher in animal food than in vegetable food. Therefore the pesticide residues in animal food should be paid more attention, namely the pesticide that is accumulated in animal body needs special attention. Meanwhile, concentrated pesticide has a relatively higher positive rate, whereas the positive rate of pesticide in food product that undergone deep processing is lower than that of the primary farm product. "Stem vegetable", "Berries fruit", "Beans", "Leafy vegetable", "Brassica vegetable", and "Tea" are rank 1 to 6 respectively in the list of positive rate of chlorpyrifos,. The fact that "Bulb vegetable", "Stem vegetable", "Leafy vegetable" and "Tuber vegetable" are all found on the list of non-conformity chlorpyrifos content in food category in 2003-2006. This shows that these vegetable categories should be highlight of vegetable safety supervision in China.3. The distribution of chlorpyrifos by region in 2003-2006 in China indicates that chlorpyrifos residue is higher in the southern area than that in the northern area in China. The top 4 at P97.5 by region are Zhuhai, Fujian, Zhejiang, Yunnan, respectively, which are all located in the South of China. The top list of the maximum chlorpyrifos residue are Chongqing, Hubei, Guangxi, Guangdong respectively. This result could be related to the climate difference between southern and northern part of China.4. As per monitoring data we collected in all groups of food, due to different objectives and different methods and different sample size may lead to different lowest detection limit. Therefore given the case of 98% residue is non-detectable, the lowest detection limit of the non-detected will be extremely important, especially when the sample size is relatively limited and this may lead to outliers. This shows that quality of data will have direct impact on assessment result and therefore assessment results will be much more reliable if data are representative and collected with clear objective.â…¡. Through point estimation of dietary exposure assessment for chlorpyrifos residue in spinach for export and for domestic consumption, conclusions are drawn as below:1. As per acute exposure assessment for chlorpyrifos:â… . the %PAD of chlorpyrifos is relatively higher in the group aged 1-6, amongst the %aPAD of the rural group aged 1-3 is 115.74 and the %PAD of the rural group aged 4-6 is 110.43 which is above 100, it shows that this group is high risk population and probably due to higher dietary intake per Kg body weight by children;â…¡. The %aPAD in male groups is relatively lower than that in female groups, and this could be that vegetable consumption in female groups is higher than in male group;â…¢. Based on assessment by region, the results show that the %aPAD of rural population in the children and adolescent group under 18 is apparently higher than urban group, and the figures in adult aged above 18 in rural group is also a bit higher than in urban group. The conclusion is related to the total vegetable consumption, differences in diet structure and body weight;â…£. Based on assessment by total population, the %aPAD of chlorpyrifos is 43.09<100 which is safe..2. As per chronic exposure assessment of chlorpyrifos:â… . The max %cPAD in urban children is 6.59 which is far below than 100 when non-detected chlorpyrifos residue replaced by LOQ, therefore it is not necessary to put the chronic assessment of chlorpyrifos under highlight;â…¡. The %cPAD of chlorpyrifos in spinach is relatively higher in female group than in male group and this is aligned with the result from acute assessment;â…¢. For children aged 1-3 and 7-10, the %cPAD in urban group is higher than in rural group, however, for people in other age group, the %cPAD in rural group has higher figure than in urban group;â…£. For different age group, if non-detected chlorpyrifos residue is replaced by LOQ and 0, the %cPAD from point estimation varies from 5-9 times.3. Comparison of assessment results from the acute and chronic exposure assessment of chlorpyrifos:acute and chronic exposure point estimation shows that the %aPAD of any group is much higher than the %cPAD. The %aPAD of the total population is 43.05 and while the %cPAD is 2.94. The risk from acute exposure assessment is 15 times higher than chronic exposure assessment. Therefore, acute toxicology of chlorpyrifos should be highlight of research and management in upcoming works.4. Difference between spinach exported to Japan and spinach for domestic consumption:results show that main difference is from process factors due to variability in China dietary structure. If Chinese consumer can follow the procedure to wash and bleach vegetable carefully, the %aPAD is 17.22 and the %cPAD is 0.69 for domestic consumer and %aPAD is 16.2 and %cPAD is 0.4 for export spinach for Japan, all data is within safe range.â…¢. Conclusions are drawn based on the probabilistic assessment for exposure of chlorpyrifos in diet:1. When non-detected data for chlorpyrifos in spinach are replaced with 0, 1/2LOQ or LOQ, probabilistic assessment shows the younger the age is, the higher for exposure of chlorpyrifos as per Kg body weight, group aged 1-6 has the highest exposure, and group aged 4-6 has the maximum exposure at percentile of 99.99. The exposure of chlorpyrifos in spinach also varies from region to region, as a result, the rural group has a relatively higher exposure than urban group and this indicates that a higher chlorpyrifos residue in food in rural area. However, the daily exposure of chlorpyrifos by age and region is below the limit and far less than ARfD.2. The distribution of exposure of chlorpyrifos in spinach is a left skew distribution. The quartile range P75-P25 shows that 50% of the population in the middle has less variability. Different exposure of chlorpyrifos by region indicates that rural group has higher level of exposure than urban group at percentile of P99, P99.9, P99.99. Where exposure level of rural group higher than urban group, there is high level of percentile (e.g. P99), there is nearly 18 times of exposure level than where percentile is low (e.g. P25). Exposure is a left skew distribution and chlorpyfrifos residue in rural area is much more serious than in urban area.3. The uncertainty analysis from probabilistic assessment on chlorpyrifos residue in spinach and in food shows that all percentiles of variability are within the 95% confidence interval. It shows 1 million sample size is sufficient to stablize the exposure percentiles and the Monte Carlo simulation has quantified the variability. If we put aside the uncertainty issue, the Monet Carlo percentiles are sufficiently stable for actual application. Meanwhile, the uncertainty analysis also shows that the higher the percentile is, the broader 95% confidence interval is and the higher the uncertainty is.4. If non-detected data is replaced with LOQ in the probabilistic assessment of chlorpyrifos in all food, the result shows the variability of the exposure in total population groups at P99.99 is 11.139 which is lower than ARfD (ARfD=100). Subgroup aged 1-3 and 4-6 has the highest exposure as 17.544 which is lower than ARfD. From the variability of exposure of chlorpyrifos in urban and rural area, it concludes that exposure in rural area is higher than in urban area and maximum exposure in rural is 30.02 which is less than ARfD.5. The food contribution analysis in the acute probabilistic assessment shows that, based on food types, the top 3 of chlorpyrifos intake in total population, urban group and rural group are:vegetable and its product, fruit and its product, potato starch and its product. In order to describe the specific contribution of chlorpyrifos intake by subgroup of food, the top 3 contributors of chlorpyrifos intake in the total population are:"young stem, leaves and flower vegetables"; "solanaceous fruit vegetable, and cucurbit"; "fresh bean". And their contribution is 81.75%,5.94% and 2.75% respectively with a sum of 90.44%. Food contribution from all group and subgroup with high exposure is same than that in total population, and this is aligned with the left skew distribution of exposure of chlorpyrifos in diet.6. Due to food processing factors and the half life of chlorpyrifos are not considered during chronic dietary exposure assessment, results show that variability at each percentile in chlorpyrifos are all less than the ADI value, however, if the FQPA coefficient is taken into account, variablity will be close to alerting limit, and this is not in accord with chronic toxicology and symptoms of chronic toxicity of chlorpyrifos. Thus we concluded that chronic toxicology probabilistic assessment needs more data support.7. When non-detected data of chlorpyrifos residue is replaced with 0,1/2LOQ or LOQ respectively, we found that it has significant effect on the mean value, however difference becomes smaller and smaller at high percentiles such as P99.9 or even P99.99. â…¥. Comparison between the results of point estimation and probabilistic assessment1. Risk assessment of chlorpyrifos in spinach and in all food shows that point estimation result from total population is that rural group aged 1-3 and 4-6, which the %aPAD is 115.74 and 110.43 respectively. The %aPAD at 99.9% percentile is 24.3 and 22.2 respectively in probabilistic assessment, and the %aPAD at 99% percentile is as small as 1.449 and 1.320 respectively. The figure shows that results from probabilistic assessment is reasonable and high risk population from acute toxicology assessment is still safe.2. The point estimation has the same result than probabilistic assessment, namely the rural group aged 1-3 and 4-6 are high risk population, and the urban group aged 1-3 and 4-6 next to it. Result of point estimation is 2-160 times higher than that of probabilistic assessment, so point estimation is quite conservative. From the point of protecting as much people as we can, result could be used as primary reference or as criteria for judging whether probabilistic assessment is necessary. Across the assessment process, we can clearly see that probabilistic assessment requires more data, software and hardware, time and resource than the point estimation. Those two methods are very important for dietary exposure assessment and can not replace each other. The probabilistic assessment is not necessary when the point estimation shows relatively little risk.3. According to risk assessment from the probabilistic assessment of acute dietary exposure assessment of chlorpyrifos in all food in China, the sub-groups with highest risk are the urban group aged 1-3, rural group aged 1-3 and 4-6, and the %aPAD is 91.197,82.895 and 83.255 respectively and all are close but less than 100. Safety factors are not taken into account for this case, therefore we concluded that exposure of chlorpyrifos for each group is within safety range. Meanwhile children aged 1-6 either in rural or urban area should be highlight in research of chlorpyrifos residue. Given research on processing factors provided in the chapter 1, we suggest consumers wash and bleach before have it and this enables great reduction of chlorpyrifos residue in food.
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