Smoke from wood fires has long been recognized as a significant health hazard. Our recent work has reported on the occurrence of waste timber previously treated by chromated copper arsenate (CCA) insecticide in the fuel supplies of informally operating caterers in the Cape Town region. The main objective of this paper is to report evidence that the burning of CCA-treated wood by informal caterers does lead to arsenic enrichment of the smoke.
Atmospheric particulate matter with aerodynamic diameter ≤ 10 μm (PM10) was collected using an Air Metrics MiniVol portable aerosol sampler onto quartz filters for durations varying from 1 h to 4 h, at 5 L/min. Smoke was first sampled under controlled conditions, in which CCA-treated samples (of hazard classes H5 and H2) and two untreated wood samples were burned. 18 field samples were collected, from Nyanga, Langa and Khayelitsha (Cape Town) and Kayamandi (Stellenbosch). The PM10 concentrations were calculated and the smoke samples were microwave-digested using nitric acid for metals analysis by ICP-AES.
Under controlled conditions, the concentrations of arsenic volatilised from (H2 and H5) were 19 and 52 μg/m3, and the As:Cu and As:Cr ratios strongly increased compared the ratios found in the timber. The lowest concentration of PM10 was found around the Nyanga taxi rank at a distance of ± 100 m from caterers, at 33 μg/m3, while the highest concentration was 8139 μg/m3 for a 1-hour sample representing occupational exposure close to wood burning fires. Arsenic was detected in 15 smoke samples. The average arsenic level of positive samples was 1.3 μg/m3. The arsenic levels measured exceed normal background levels, which have been reported by the WHO to be 0.02–4 ng/m3 in rural air and up to 30 ng/m3 in urban air.