Evaluation of potential adverse health effects resulting from chronic domestic exposure to the organophosphate insecticide methyl parathion

Methyl parathion (MP) was used illegally to spray homes for insect control over approximately an 8-yr period. In an attempt to determine if there were any adverse health effects from this, health-screening evaluations were performed on 353 individuals living in homes that were illegally sprayed. The average subject spent 15.5 h a day in the home. Subjects from homes with high levels of MP (exposure group) were compared to controls that lived in homes with minimal or no MP. Subjects were aware of the levels of MP found in their homes and recall bias was likely. There were no significant differences in the symptoms reported or by the physician assessment of subacute or chronic toxicity between those in the exposure group and controls. No significant differences were found in growth and developmental evaluations. Three subjects were identified who most likely suffered acute toxicity from the initial exposure and were not appropriately diagnosed and treated. Cholinesterase determinations also did not differ between those in the exposure group and controls. When subjects from the exposure group were stratified by the level of MP in their home, those from homes with the highest levels appeared to have an increased likelihood of subacute toxicity and reported an increased number of neuropsychiatric symptoms (OR 2 for both evaluations).