Agricultural pesticides, application practice

It is correct to note that the specific tolerance levels requested by the manufacturer are determined solely on the basis of agricultural practices and not upon potential human health considerations. As such, tolerances represent enforcement tools to determine whether pesticide applications were made in accordance with the law but should not be considered as safety standards. In the case where a pesticide is used properly, the resulting residue level should be below the tolerance level. Residues detected in excess of the established tolerance are likely encountered only in cases where applications are not made in accordance with the legal directions. Results obtained from federal and state monitoring programs demonstrate that the incidence of residues detected in excess of tolerances is very low and suggest that most pesticide applications are made legally. 

In addition to the need for scientific improvements to allow probabilistic risk assessments to be properly performed and interpreted, there also exists a need to educate stakeholders about what the US system for tolerance establishment and monitoring does and does not do. In simplest terms, the US system can be described as a food quality system but not necessarily a food safety system. This results from the fact that the pesticide tolerances are not safety standards but rather exist as enforcement tools that allow an assessment of how well pesticide application regulations are adhered to. Violative residues demonstrate the likelihood of pesticide misuse but should not be considered, in the vast majority of cases, to represent unsafe residues. Safety considerations govern whether or not the use of pesticides on specified commodities will be permitted tolerances, when granted, serve as indicators of good agricultural practices rather than as toxicological benchmarks. 

Occupational pesticide exposure holds a peculiar status within the field of occupational health and safety, both from a scientific and regulatory perspective. Methods for personal monitoring of dermal exposure first arose in the context of pesticide applications in agriculture, pioneered by scientists in the USA Public Health Service (Batchelor and Walker, 1954 Durham and Wolfe, 1962). These methods gained worldwide recognition in the early 1960s, and remain a component of exposure assessment practice today. This work pre-dated most personal monitoring methods that were developed for industrial workplaces. 

Details of the source of the plant, such as country and/or region (also state and province, if applicable) of origin, whether it was cultivated or collected from the wild and, where applicable, method of cultivation, dates and conditions of harvesting (e.g. whether there was extreme weather), collection procedures, collection area, and brand, quantity and date of pesticide application, as required by the WHO Guideline on good agricultural and collection practices (7). 

Paice, M.E.R., Miller, P.C.H. and Power, J.D. (1993) A practical pesticide injection metering system for agricultural sprayers. Proceedings, ANPP-BCPC Second International Symposium on Pesticide Application Techniques, Strasbourg, 1, 313-320. 

However, there is no general requirement that enforcement methods need to monitor all metabolites of an active ingredient. The primary purpose of enforcement methods is to detect violations of good agricultural practice. For this purpose, residue levels found in samples from the market (so-called Market Basket Surveys) have to be compared with MRLs, which are derived from residue concentrations found in supervised trials. It is not necessary for this comparison to be based on the total pesticide residue. Most often the choice of a single compound (e.g., parent or primary metabolite) as a marker of the total pesticide residue is more feasible. Method development and the later method application are much easier in that case. Only for intake calculation purposes, e.g., when the daily intake of pesticide residues (calculated from the results... 

Examples 3 and 4 illustrate a potential application of allelo-pathic chemicals in today s agricultural practices, as illustrated in Figure 3 to plant allelopathlc plants as a cover crop in the field, especially for tree crops such as peach and citrus. Such plants produce allelopathlc chemicals to control soil pests such as nematodes. This approach will be appreciated today, because there is no effective agent to control soil pests on a field scale and, as has been noted, there is no economic incentive for a chemical company to develop a minor-crop pesticide. 

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