Abstract

Three types of mosquito repellent [two different mosquito coils containing allethrin 0.1% w/w and transfluthrin 0.03% w/w, an aerosol sample containing a combination of two pyrethroid molecules (deltamethrin 0.02% w/w + allethrin 0.13% w/w) and two different mosquito mats containing esbiothrin 2.0% w/w and prallethrin 1.5% w/w as active ingredients] were individually subjected to use in a closed room. Air samples from the room were drawn at different time intervals (15, 30 and 45 min, and 1, 2, 4, 6 and 8 h) uniformly from three different positions in the room (top, middle and bottom) with the pyrethroid contents analysed using gas chromatography-electron capture detection (GC-ECD). Analysis of air samples showed maximum concentrations of the pyrethroid residues allethrin (0.0120 ppm), transfluthrin (0.0134 ppm), deltamethrin (0.0057 ppm), allethrin (0.080 ppm), esbiothrin (0.015 ppm) and prallethrin (0.0138 ppm) within 30–45 min of use. The drop in residue content was significant with time. At the end of a 6 h period, most of the residues had dissipated to below 0.0001 ppm. Further significant differences were observed in the residue contents tested at different points within the room. Studies were compared with the experimental results obtained when the mosquito repellents were tested with air circulation in the room.