Risk assessment of the use of deltamethrin on bednets for the prevention of malaria

Risk assessments covering the use of the pyrethroid, deltamethrin, on bedne ts for the prevention of malaria have been conducted The toxicity of deltam ethrin in humans and animals is reviewed following both dermal and oral exp osure. The no-adverse-effect level (NOEL) for exposure via the dermal route was 1000 mg/kg body weight/day. From this an acceptable exposure level (AE L) of 10 mg/kg body weight/day has been derived. The NOEL for exposure via the oral route was 1 mg/kg body weight/day, with exposures above this causi ng neurotoxic effects in animals. This NOEL has been used to derive margins of safety compared with predicted exposures. While direct skin contact doe s not seem to cause systemic toxicity in humans, it can cause burning, numb ness and tingling of the skin, which is a local effect. This too is taken i nto account in the risk assessments. The risk assessments cover those treat ing bednets, on an intermittent or regular basis, the washing of treated ne ts, sleeping under treated nets (infants, children and adults). Worst case scenarios for each of these situations show that dermal exposures are low ( one-tenth or less of the AEL) and the margins of safety for systemic exposu re derived from oral data are acceptable, ranging from 10 to 3300. The bene fits of the use of treated bednets in reducing morbidity and mortality from malaria are considerable and it can be concluded that the risk:benefit rat io is very favourable. (C) 2001 Elsevier Science Ltd. All rights reserved.