Household insecticide use in Amazonian riverine communities: a population-based cross-sectional survey in Belem, Brazil

Background: Household insecticides are widely used for domestic pest control, yet exposure patterns in traditionally underserved populations remain poorly characterized. In the Brazilian Amazon, data on use patterns among older adults living in riverine communities are particularly scarce. Objective: To describe the prevalence, frequency, duration, application practices, and types of household insecticides used by older adults living in near-urban riverine insular communities in the Brazilian Amazon. Methods: Cross-sectional, population-based door-to-door survey conducted from August 2022 to July 2025 in four islands (Cotijuba, Mosqueiro, Outeiro, and Combu) in the city of Belem, Brazil. All residents aged 60 years or more registered in the primary care system were invited to participate. Trained interviewers administered an in-person standardized questionnaire to participants on current household insecticide use, frequency, duration, self-application, protective equipment, insecticide types, and product brands. Results: Among 1,101 screened individuals, 1,084 were included (median age at evaluation: 68 years). Overall, 78.4% reported current use of household insecticides. Weekly or more frequent use was reported by 58.9%, and 33.4% reported use for more than 5 years. Self-application was common (57.5%), whereas use of protective equipment was rare (8.2%). Aerosol sprays were the most frequently reported type (39.4%). Commonly recalled aerosols contained pyrethroid mixtures including cypermethrin, imiprothrin, prallethrin, and transfluthrin. A substantial proportion of participants reported using unregulated products and veterinary-only insecticides for household purposes. Conclusions: Household insecticide use is highly prevalent and frequent in Amazonian riverine communities, with minimal use of protective equipment and substantial irregular practices, underscoring the need for targeted risk communication and surveillance.