ASSESSMENT OF EXPOSURE TO MALATHION AND MALAOXON DUE TO AERIAL APPLICATION OVER URBAN AREAS OF SOUTHERN CALIFORNIA

The state of California conducted aerial applications of malathion (MA ) bait over urban areas in the southern California air basin in order to eradicate the Mediterranean Fruit Fly (Ceratitis capitata). Concern about the potential human health effects of this activity prompted a risk assessment conducted by the California Department of Health Servi ces. Estimates of potential human exposures to MA and its primary brea kdown product, malaoxon, (MO) are based on assumptions of daily human activities which influence the rate of contact with MA and MO. Several exposure scenarios, representing a range of activity levels from sede ntary to very active, are used as surrogates for a variety of human ac tivities. For each exposure scenario, acute dose rates are calculated using both the mean and the mean plus 2 standard deviations (SD) (98% upper confidence limit (UCL)) of measured environmental values. Chroni c dose rates are calculated using long-term averages incorporating deg radation and multiple applications at 14 day intervals, and the estima ted 98% UCL for these averages. Based on this model, estimated adult d ermal doses (1-246 mug/kg-d) are up to about 2000-fold higher than the estimated inhalation doses (0.01-0.1 mug/kg-d) but are comparable to the doses from ingestion of contaminated unwashed backyard vegetables (30-80 mug/kg-d) . For the individual who does not consume backyard ve getables, therefore, almost the whole dose of MA or MO would be due to contacting contaminated surfaces with skin.