Cytogenetic response without changes in peripheral cholinesterase enzymes following exposure to a sheep dip containing diazinon in vivo and in vitro

Occupational exposure to organophosphorus insecticides (OPs), such as diazi non, may be monitored by the measurement of the activity of peripheral chol inesterase enzymes, including erythrocyte acetylcholinesterase (EAChE) and plasma or serum cholinesterase (plasma or serum ChE). Exposures have also b een measured by the analysis of dialkyl phosphate metabolites of OPs in uri ne. The potential health risks associated with exposure, especially those o f a neurological nature, may then be estimated, and appropriate measures to reduce or eliminate exposures can be implemented. There is evidence that s ome OP pesticides may have in vivo genotoxic effects, suggesting a possible link with cancer with long term or repeated heavy exposures. This paper de scribes work performed in 17 subjects with a single or two exposures to a s heep dip containing diazinon. Urine samples revealed OP metabolites dimethy lphosphate (DMP), dimethylthiophosphate (DMTP), diethylphosphate (DEP) and diethylthiophosphate (DETP) in 37% of subjects at low levels which were not elevated after exposure. EAChE and plasma ChE were also unchanged before a nd after exposure, and were similar to those measured in unexposed control groups. Sister chromatid exchanges (SCE), a marker of chromosome damage, wa s significantly elevated in peripheral blood lymphocytes after exposure com pared with before. SCE were unchanged in a group of non-occupationally expo sed workers. In vitro studies with both authentic diazinon (98%) and diazin on in a sheep dip formulation (45%) showed increased SCE and decreased repl icative indices, suggesting toxic and genotoxic effects of diazinon. (C) 20 00 Published by Elsevier Science B.V.