Pyriproxyfen is a pyridine insecticide that mimics juvenile growth hormone, which prevents larvae from developing into reproduction-capable adults. The LD50 of pyriproxyfen in rats is >5,000 mg/kg, >1,300 mg/cubic meter/4 hours, and >2,000 mg/kg through oral, inhalation, or percutaneous dosing, respectively.1 It is used as a larvicide in the drinking water of 11 municipalities in Brazil and rumors suggested it may be correlated with the increase in cases of microcephaly in Brazil.2 The acceptable daily intake determined by the World Health Organization is 0.3 mg/L.3 The prevalence of microcephaly in Brazil is not higher in municipalities that use pyriproxyfen in the water supply, compared with municipalities that use the larvicide Bti.2 In addition, in zebrafish, even very high doses (0.1 ?g/ml, compared with 0.01 ?g/ml used in practice for pest control) pyriproxyfen does not induce microcephaly or other brain malformations.4 Formulations containing pyriproxyfen are used for flea control in dogs and as an insecticide for ants.5,6
1.Tomlin, C.D.S.The pesticide manual: A world compendium: Incorporating the agrochemicals handbook(1995) 2.de Alburquerque, M.P.M., de Souza, W.V., Mendes, A.d.C.G., et al.Pyriproxyfen and the microcephaly epidemic in Brazil - an ecological approach to explore the hypothesis of their associationMem. Inst. Oswaldo Cruz111(12)774-776(2016) 3.Pyriproxyfen in drinking-water: Background document for development of WHO guidelines for drinking-water qualityWHO/SDE/WSH/07.01/10(2007) 4.Dzieciolowska, S., Larroque, A.-L., Kranjec, E.-A., et al.The larvicide pyriproxyfen blamed during the Zika virus outbreak does not cause microcephaly in zebrafish embryosSci. Rep.740067(2017) 5.Ross, D.H., Arther, R.G., von Simson, C., et al.Evaluation of the efficacy of topically administered imidacloprid?+?pyriproxyfen and orally administered spinosad against cat fleas (Ctenocephalides felis): Impact of treated dogs on flea life stages in a simulated home environmentParasit. Vectors.5192(2012) 6.Vail, K.M., and Williams, D.F.Pharaoh ant (Hymenoptera: Formicidae) colony development after consumption of pyriproxyfen baitsJ. Econ. Entomol.88(6)1695-1702(1995)