Seasonal influence on urban dust PAH profile and toxicity in Sydney, Australia

Road dust is one of the major threats to the urban environment due to wash-off of dust to the surrounding catchments during wet weather period. The dust contains wide range of toxic contaminants such as heavy metals, polycyclic aromatic hydrocarbons (PAHS) and endocrine disrupting chemicals. Among the toxic contaminants, PAHs are of environmental concern due to their potential carcinogenic and mutagenic effect besides endocrine disruptive behaviour. Eighteen road dust samples from Sydney were collected in different time periods for a year and analysed for 16 US EPA PAHS. Total PAHs content range in the dust was 9-105 pg/g. Total and individual PAH contents were highest in the finest size fraction (<75 microm) and in winter compared to the other seasons. The PAH profiles in the different particle sizes were similar but different between the four seasons. The concentrations of higher molecular weight PAHS (4- and 5-rings) were much greater than the concentrations of lower molecular weight PAHs (2- and 3-rings). Toxicity equivalency factor application showed that the longer the dry weather period the higher the total PAHs content and toxicity in the dust.