Accreditation of analytical laboratories and proficiency testing: experiences from Thailand on the issues of pesticide analysis.

Thailand, the economic growth of which largely depends on agriculture-based industry, recognizes the importance of international standards for harmonization of international food trade and for protection of human health from chemicals used as food additives or those present as contaminants. Pesticides which are widely used in Thailand are the anticholinesterase pesticides, pyrethroids, coumarin derivatives, bipyridinium salts, and to some extent organochlorine compounds such as DDT in malaria control. Proficiency testing and accreditation of laboratories are recognized as effective means to ensure quality and validity of data and to enable adequate risk assessment of pesticide residues in food, work environment and environment in general.

Exposure evaluation is a crucial step for quantitative risk assessment of methomyl.

Methomyl, methyl N-[[(methylamino)carbonyl]oxy]ethanimidothioate is a carbamate insecticide with anticholinesterase activity. As a broad spectrum insecticide, it is one of the most frequently used pesticides in tangerine orchards in Thailand. Although methomyl is said to be rapidly eliminated from experimental animals (1) high incidence of acute poisonings was reported among patients occupationally exposed to a powder formulation of methomyl (2, 3).