Neurologic function among termiticide applicators exposed to chlorpyrifos

Chlorpyrifos is a moderately toxic organophosphate pesticide. Houses and la wns in the United States receive a total of approximately 20 million annual chlorpyrifos treatments, and 82% of U.S. adults have detectable levels of a chlorpyrifos metabolite (3,5,6-trichloro-2-pyridinol; TCP) in the urine. The U.S. Environmental Protection Agency has estimated that there are 5,000 yearly reported cases of accidental chlorpyrifos poisoning, and approximat ely one-fourth of these cases exhibit symptoms. Organophosphates affect the nervous system, but there are few epidemiologic data on chlorpyrifos neuro toxicity. We studied neurologic function in 191 current and former termitic ide applicators who had an average of 2.4 years applying chlorpyrifos and 2 .5 years applying other pesticides, and we compared them to 189 nonexposed controls. The average urinary TCP level for 65 recently exposed applicators was 629.5 mu g/L, as compared to 4.5 mu g/L for the general U.S. populatio n. The exposed group did not differ significantly from the nonexposed group for any test in the clinical examination. Few significant differences were found in nerve conduction velocity, arm/hand tremor, vibrotactile sensitiv ity, vision, smell, visual/motor skills, or neurobehavioral skills. The exp osed group did not perform as well as the nonexposed group in pegboard turn ing tests and some postural sway tests. The exposed subjects also reported significantly more symptoms, including memory problems, emotional scares, f atigue, and loss of muscle strength; our more quantitative tests may not ha ve been adequate to detect these symptoms. Eight men who reported past chlo rpyrifos poisoning had a pattern of low performance on a number of tests, w hich is consistent with prior reports of chronic effects of organophosphate poisoning. Overall, the lack of exposure effects on the clinical examinati on was reassuring. The findings for self-reported symptoms raise some conce rn, as does the Ending of low performance For those reporting prior poisoni ng. Although this was a relatively large study based on a well-defined targ et population, the workers we studied may not be representative of all expo sed workers, and caution should be exercised in generalizing our results.