Characterization of Risk Associated with Occupational Exposure to Mevinphos. R. C. Cochran, Tareq A. Formoil, Marilyn H. Silva, Thomas P. Kellner, Carolyn Lewis, and Keith Pfeifer, Dept. of Pesticide Regulation, 1020 N St., Sacramento, CA 95814-5604
Monitoring data, and calculations from monitoring data for surrogate active ingredients with similar application rates and chemical properties, indicated mean work-related absorbed daily dosages (ADDs) ranged from negligible for some vegetable harvesters, to 11.0 ug/kg-day for apple harvesters. The 95th percentile of ADDs ranged from 1.1 ug/kg-day for helicopter pilots, to 33.8 ug/kg-day for mixer/loaders in helicopter operations. Potential chronic occupational exposure (average annual daily dosage--AADD) ranged from negligible for some vegetable harvesters to 0.63 ug/kg-day for apple harvesters. A 1-day NOEL for cholinergic signs in humans (0.025 mg/kg) was used to evaluate the risk of potential acute occupational exposures. A NOEL for brain cholinesterase inhibition in rats (0.025 mg/kg-day) was used for the assessment of potential chronic occupational exposure to mevinphos. The margins of safety (MOSs) for mean acute occupational exposures, based on the NOEL of 0.025 mg/kg for human cholinergic signs, ranged from 2 (apple harvesters) to 625 (flaggers in enclosed vehicles). When the 95th percentile of the short-term exposures were considered for each of the job categories, the MOSs ranged from less than 1 (mixer/loaders involved in helicopter applications) to 23 (helicopter pilots). MOSs for chronic occupational exposure, based on a NOEL of 0.025 mg/kg-day for inhibition of brain cholinesterase activity in rats, ranged from 40 (apple harvesters) to 8,333 (flaggers in enclosed vehicles).