An estimated 700 million people suffer from mosquito-borne diseases worldwide. Various types of mosquito repellents are widely used to prevent mosquito bites. The objectives of this study were (1) to measure the indoor levels of particulate matter < 2.5 μm in mean aerodynamic diameter (PM2.5) and carbon monoxide (CO) during the burning of mosquito coils (MCs) and study the impact of indoor ventilation patterns; and (2) to study and compare the prevalence of respiratory ailments in homes using different types of mosquito repellents.
Indoor PM2.5 and CO levels were measured inside a bedroom during the burning of MCs keeping the window and/or door open/closed over a 6-h duration. A cross-sectional survey was conducted in three villages where 465 individuals were administered a questionnaire that captured demographic details, type and duration of mosquito repellents used, and prevalence of respiratory symptoms and diseases.
Fifty-three percent of the subjects burned MCs on most days of the week, and 63% did so with their doors and windows closed. Burning of MCs produced very high levels of PM2.5 (1,031 μg/m3 mean, 1,613 μg/m3 peak) and CO (6.50 parts per million (ppm) mean, 10.27 ppm peak) when both the door and window were closed. These levels reduced by around 50% when the window was opened and > 95% when both the window and the door were opened. The prevalence rates of respiratory symptoms and diseases were higher in subjects using MCs, although not statistically significant. Those living in smaller homes and using MCs had significantly greater morbidity.
Burning of MCs produces indoor levels of PM2.5 and CO that are higher than those reported during the burning of biomass fuels for cooking purposes and may be associated with respiratory morbidity.