Probabilistic human health risk assessment of trace metal exposure in Australian homes: insights from a legacy industrial region

Urbanization and industrial activity contribute to environmental contamination, increasing potential health risks for residents via trace metal exposure. This study used a probabilistic human health risk assessment (PHHR) to evaluate trace metal exposure in Australian homes, using garden soil data from 9548 homes and indoor dust samples from 2341 homes. A focused assessment of 75 homes in the historically industrial Illawarra region was included to investigate possible legacy contamination. PHHR captures variability in exposure frequency, contaminant concentrations, and intake rates, unlike deterministic models. Exposure was assessed through ingestion, inhalation, and dermal contact pathways. In Illawarra, garden soils had significantly higher mean concentrations of Cr, Cu, Mn, Ni, and Zn compared to national levels (p < 0.05). Indoor dust from older homes and areas near former industrial sites also showed elevated levels of As, Cr, Cu, Mn, Pb, and Zn (p < 0.05). Children consistently showed greater health risks than adults, particularly from indoor dust ingestion. Nationally, non-carcinogenic risk (hazard index, HI) exceeded the threshold (HI > 1) above the 98th percentile in soil (HI max = 4.98 children; 3.05 adults) and above the 86th percentile in dust (HI max = 8.48 children; 7.02 adults). Carcinogenic risks (TCRs) exceeded 1 × 10⁻⁴ above the 95th percentile in dust. In Illawarra, exceedances were rare (< 0.5%), with HI > 1 observed only above the 99th percentile in dust. These findings highlight indoor dust is a critical trace metal source and the value of PHHR in identifying high-risk cases that may otherwise be overlooked.