Can toxins persist in house dust and soil years after an episodic fire event?

Objective Communities exposed to smoke and ash from severe industrial fires often express concern that chemicals from the fire episode pose an ongoing risk to their health by persisting in and around the home environment. While previous studies have utilised house dust and soil samples to estimate exposure to contaminants resulting from fire and industrial emissions up to five years post-event, the evidence for persistence is limited. This study aimed to investigate if evidence of contamination attributable to a mine fire episode (Latrobe Valley, Victoria, Australia) could be observed in those medium three years later. Methods In 2017, eighty-five participants in a birth cohort study established post-fire in the Latrobe Valley provided indoor vacuum dust and garden soil samples. The samples were analysed for a suite of polycyclic aromatic hydrocarbons and chemical elements, including barium and magnesium, which had been previously identified as markers of fire emissions in roof cavity dust. The spatial distribution of these elements and compounds was compared with the distribution of smoke and ash from the 2014 fire, after accounting for housing characteristics. Results There was no evidence of persistent contamination of soil or indoor dust samples that could be attributable to this severe fire and pollution episode three years previously. These findings can be helpful in reassuring affected communities about the risk of long-term persistence of potentially harmful substances. Conclusions Household soil and dust may be more useful for understanding exposures from contemporaneous or persistent pollution sources such as road networks or industrial facilities.