Exposure and health risk assessment for farmers occupationally exposed to chlorpyrifos in Sri Lanka; and drinking water and house dust analysis for chlorpyrifos

This study was designed to assess chlorpyrifos exposure of a group of farmers by determining internal dose associated with a given application of this insecticide. This involved the monitoring of urinary levels of 3,5,6 trichloro-2-pyridinol (TCP), the major metabolite of chlorpyrifos. Incidental exposure was evaluated by determining the levels of chlorpyrifos and TCP in drinking water and house dust.; Nineteen full-time farmers from Kandy district, Sri Lanka, growing long-squash or bitter melon during the 2000 vegetable season (April–June) participated in the study. Information concerning their health history, agricultural practices, family background and pesticide-related issues were obtained using a questionnaire. All farmers used knapsack sprayers for applying a chlorpyrifos EC formulation. The amount of chemical applied, time required, and the safety precautions used were noted.; One urine sample was taken prior to application followed by three samples a day for 5 days post application from each farmer. Urine samples were extracted with hexane and analyzed for TCP using a gas chromatograph fitted with an electron capture detector. The limit of detection for TCP in urine was 6ng/mL.; TCP levels peaked within 24 hours post application and returned to the baseline after 5 days. Total TCP voided ranged from 71 to 299μg (average of 190.4ug) per 5g of creatinine, equivalent to a calculated internal dose of 0.002–0.0084mg/kg (average 0.0055mg/kg) chlorpyrifos. It was assumed that 90% of the internal dose was voided in urine in 5 days. The dermal dose ranged from 4.8 to 19.6μg/cm2 on exposed skin. The elimination half-life of the urinary TCP metabolite was 31.2 hours. The internal dose was correlated with the amount of active ingredient used (p < 5 × 10−7), the use of leaky tanks (p < 0.005), and the use of protective clothing (p < 0.005). Hazard quotient for cholinesterase inhibition based on the EPA reference dose for chlorpyrifos ranged from 0.8 to 2.7 and the margin of safety from 3.6 to 14.3 for the exposed farmers. None of the farmers were found to have symptoms of acute or sub-chronic poisoning in the medical examination carried out at the end of the season.; Drinking water was collected from three wells, and dust was collected as floor wipes from three houses located adjacent to treated areas. Chlorpyrifos was not detected in well water at levels that could be quantitated (minimum detection limit was 7ng/L). TCP was detected in well water 9 to 10ng/mL. Although some chromatograms suggest the presence of chlorpyrifos in some house dust samples (minimum detection limit 13ppb), a comparison of the responses on two different columns did not provide convincing evidence for the presence of chlorpyrifos. Failure to detect significant amount of chlorpyrifos in water and house dust was probably due to rapid break down due to high soil temperature and pH. Water and house dust did not add to the farmers' occupational exposure.