The effect of wood burning on concentrations of arsenic in household dust in Auckland, New Zealand

Abstract

Ambient arsenic levels in some areas of Auckland have been found to exceed the New Zealand air quality guidelines for health. While arsenic levels outdoors have been well investigated in New Zealand, little is known about indoor concentrations. As modern populations spend most of their time indoors, it is important to understand the presence and characteristics of this toxic metalloid in indoor environments. The aim of this thesis was to measure indoor concentrations of arsenic and investigate the factors affecting concentrations, particularly the burning of treated timber. Samples of household dust were submitted from participants across Auckland via the citizen science programme DustSafe over both the summer and winter periods. The concentrations of As, Cr, Cu, Mn, Ni, Pb and Zn were then measured and used for further analysis. In addition, participants were asked to complete a questionnaire describing their household characteristics, behaviours and observations of wood burning in their neighbourhood which may contribute to indoor arsenic levels. Arsenic was higher in regions with greater numbers of wood burners and where participants more frequently detected woodsmoke. Interestingly, arsenic concentrations found did not differ significantly between seasons, suggesting a source of arsenic in the summer. Arsenic was not significantly associated with participant household characteristics (as determined from questionnaires), except for the presence of indoor pets. This could be due to the track-in of outdoor arsenic residue by household pets, originating from treated timber structures or outdoor soils. Multivariate receptor modelling of the data resulted in chemical profiles with high contributions from arsenic and were similar to those of a study carried out previously in New Zealand. These profiles were attributed to biomass burning in Auckland, suggesting that the burning of treated wood is a source of indoor arsenic. The results of this study suggest that levels of indoor arsenic in Auckland homes may exceed soil guidelines, and therefore negatively affect human health. Decreasing the amount of treated wood burned may reduce indoor arsenic levels. Future studies should further investigate presence of indoor pets on indoor arsenic levels, as this was the only non-wood-burning factor to significantly affect arsenic concentrations.