Journal of Exposure Science & Environmental Epidemiology https://doi.org/10.1038/s41370-019-0132-7 ARTICLE Persistence of indoor permethrin and estimation of dermal and non-dietary exposure Lia Emi Nakagawa 1 ● Cristiane Mazarin do Nascimento 1 ● Alan Roberto Costa 1 ● Ricardo Polatto 1 ● Solange Papini 2 Received: 26 July 2018 / Revised: 7 January 2019 / Accepted: 15 February 2019 © Springer Nature America, Inc. 2019 Abstract Pesticides applied indoors may persist longer than they would in outdoor environments, making people more vulnerable to the risk of exposure. Permethrin is a pyrethroid insecticide used in agricultural, residential, and public health sites, and is commonly detected in indoor environments. The objectives of this study were to evaluate the persistence of permethrin indoors and to estimate the levels of possible dermal and non-dietary exposure to this insecticide. Permethrin was applied on aluminum foil and kept in a glass chamber and a test house for 112 days; its concentration was measured at application and after 28, 56, and 112 days. Permethrin persisted for the entire 112 days in concentrations equal to a maximum of 89.6% of the initial concentration. We observed low levels of human dermal and non-dietary exposure to permethrin. Keywords Pesticide residue ● Indoor pesticide level ● Indoor pesticide exposure ● Pyrethroids ● Endocrine disruptors Introduction Pyrethroids are currently the most prevalent household insecticides [1]. They have exceptionally low vapor pres- sure, show high absorption onto materials such as textiles and dust, and are persistent indoors with half-lives of up to 10 years [2]. Insecticides applied in indoor environments, such as residences and schools, may persist for far longer than they would in outdoor environments. The longer persistence of insecticides indoors is ascribed to diminished or filtered sunlight, reduced moisture and air movement, and lack of soil microorganisms [3]. Pesticides can accumulate on indoor surfaces, in dust, and in or on children’s toys [4]. As people spend up to 95% of their time indoors [5], the home environment could be a potential source of passive or active exposure to toxicants for residents, particularly children and other vulnerable subgroups [6]. Permethrin is a pyrethroid registered for use in agri- cultural areas and in non-agricultural sites, such as resi- dences, buildings, and by public health programs (e.g., as a mosquito adulticide) [7]. Approximately 900,000 kg of permethrin is applied annually in the United States, of which most (~600,000 kg) is used in non-agricultural areas; 55% is applied by professionals, 41% by homeowners in residential areas, and 4% by public health programs [7]. Permethrin is persistent in the environment [7] and several studies have indicated that permethrin is one of the most commonly detected pesticides in homes [8–14]. Permethrin is classified as a Category III chemical for acute oral and dermal toxicity, is a potential endocrine disruptor [15, 16], and is classified as “likely to be carcinogenic to humans” through the oral route [7]. The objectives of this study were to evaluate permethrin persistence indoors and to estimate levels of possible dermal and non-dietary exposure to the insecticide when applied in a glass chamber and a test house. Materials and methods Permethrin persistence This experiment was conducted between August 2014 and December 2015 in São Paulo, Brazil. The persistence of permethrin was evaluated in two situations: in a glass * Lia Emi Nakagawa nakagawa@biologico.sp.gov.br 1 Biological Institute, São Paulo, São Paulo, Brazil 2 Municipal Secretariat of Health, São Paulo, SP, Brazil Supplementary information The online version of this article (https:// doi.org/10.1038/s41370-019-0132-7) contains supplementary material, which is available to authorized users. 1234567890();,: 1234567890();,: