DDT and HCH residues in indoor air arising from their use in malaria control programmes

Samples of air from rooms in a residential and rural environment, treated with either DDT or HCH at rates recommended for mosquito control under the National Malaria Eradication Programme of India, i.e. 2 and 3 g m-2, respectively, were analyzed for the residues of these insecticides. During the 8-month sampling period, DDT and HCH levels in indoor air ranged from 1.0 to 14.6 and 0.9 to 2000.1 micrograms m-3, respectively. After an initial fall, residues of DDT showed an increase again and were 5.9 micrograms m-3 in samples collected 240 days after the initial application. In contrast, HCH residues declined at a fast rate in a few days after application and remained low at the time of subsequent samplings. HCH residues were present chiefly in the vapour phase throughout the study. Thirty-four to seventy-eight percent of DDT residues were found in the particulate phase in the samples collected up to 64 days after its application and exclusively in the vapour phase at the time of later samplings. Apart from the contamination of food and feed commodities stored in premises treated for malaria control by absorption of insecticides present in the indoor atmosphere, the residues of these persistent compounds in air are also likely to result in low level pollution of the surrounding and distant environmental media by their dispersion in the global ecosystem.