Contributions of inhalation and dermal exposure to chlorpyrifos dose in Egyptian cotton field workers

Objective: Chlorpyrifos exposures were assessed in 12 Egyptian cotton field workers. Methods: 3,5,6-trichloro-2-pyridinol (TCPy) was measured in 24-hour urine samples to estimate absorbed dose. Workshift air samples were used to calculate chlorpyrifos inhalation dose. Results: Patches on legs had the highest chlorpyrifos loading rates among body regions sampled. Geometric mean chlorpyrifos air concentrations were 5.1, 8.2, and 45.0 mu g/m(3) for engineers, technicians, and applicators, respectively; peak TCPy urinary concentrations were 75-129, 78-261, and 487-1659 mu g/l, respectively; geometric mean doses were 5.2-5.4, 8.6-9.7, and 50-57 mu g/kg, respectively, considering TCPy excretion half-life values of 27 and 41 hours. All worker doses exceeded the acceptable operator exposure level of 1.5 mu g/kg/day. An estimated 94-96% of the dose was attributed to dermal exposure, calculated as the difference between total dose and inhalation dose. Discussion: Interventions to reduce dermal exposure are warranted in this population, particularly for the hands, feet, and legs.