Determination of emission characteristics of volatile compounds from mosquito repellents (MRs) by headspace and chamber methods, and indoor levels related to use of MRs

Abstract

Although the use of mosquito repellents (MRs) may lead to several adverse health effects, very limited information is available on exposure to their emissions. As such, the present study evaluated the emission characteristics of volatile pollutants from three different types of MRs (coil, mat, and liquid-vaporiser types) by headspace and/or chamber methods and measured apartment bedroom levels associated with the use of the MRs. By means of a headspace test, 18 to 22 compounds were tentatively identified from mat and liquid MRs. Six toxic/hazardous compounds identified in this headspace test were chosen as target compounds for a further chamber-emission test. An empirical equation was well fitted with time-series concentration levels in a small-scale chamber for all test MRs. Based on the chamber study, the coil MR exhibited the highest emission rate for the target compounds, with the exception of naphthalene, followed by liquid and mat MRs. It is noteworthy that naphthalene was emitted from the liquid MR only at a high emission rate (2.4 mg h−1). A comparison of apartment bedroom levels with predicted values, which were estimated by using the calculated emission data and the one-compartment mass balance equation, suggested that predictions obtained from the chamber study were similar to, or larger than, the measured bedroom levels. Furthermore, the apartment bedroom measurements suggested that the use of coil MR could significantly elevate the indoor levels of four compounds (benzene, ethyl benzene, and m, p-xylene) by up to 1.8 to 1.9 times, while the use of liquid MR could significantly increase the indoor levels of naphthalene by up to 4.2 times. The current findings can provide valuable information for the estimation of the population inhalation exposure to these emissions in indoor environments, and enhance the selection of safer MRs.