Safety of malathion dusting powder for louse control.

Because some strains of body lice are resistant to DDT and gamma-BHC, there is need for other effective, safe chemicals to control them. Malathion is known to be effective at a concentration of 1%. To test its safety, the bodies and clothing of 39 men were dusted 5 times a week for 8-16 weeks with talcum powder containing 0, 1%, 5%, and 10% malathion. Complaints about odour and skin irritation were roughly proportional to dosage. No change in blood cholinesterase activity was found, except perhaps with 10% powder. Urinary excretion of malathion-derived material was proportional to dosage. No other changes attributable to malathion were observed and the compound is considered safe for control of head and body lice.