An investigation of the safety of cotton reentry after organophosphate application.

Twelve cotton insect scouts were monitored during an entire pesticide application season by weekly determinations of para-nitrophenol excretion and biweekly cholinesterase measurements. These data were compared to weekly reentry intervals and pesticide application rates to study the validity of a 48-hr minimum reentry interval for methyl parathion-treated cotton. Methyl parathion represented 54.2% of the total amount of pesticide used with toxaphene 35.3%, ethyl parathion 4.1%, and other 6.4%. A significant decrease in erythrocyte and plasma cholinesterase was observed during initial exposure but during peak exposure the cholinesterase levels had returned to normal. The maximum mean amount of methyl and ethyl parathion absorbed by calculation from PNP excretion was 0.95 mg/24hr (n = 12). Twelve percent of all reentries were within two days and during one week 48% occurred during the first two days after pesticide application.