Health risk assessment and source tracking of heavy metal exposure from indoor settled dust in an environmentally vulnerable area of the Republic of Korea

Accelerated urban and industrial expansion has intensified anthropogenic activities, increasing the emission and accumulation of hazardous substances in air, water, and soil. This study assessed health risks from heavy metals in indoor settled dust collected from Myodo-dong, Yeosu, Republic of Korea, by estimating exposure via inhalation, dermal contact, and ingestion, deriving protective exposure limits, and identifying emission sources using multivariate analysis. Indoor settled dust samples from 20 of 50 households showed elevated heavy metal concentrations, with zinc (Zn) having the highest mean level (4,912.01 µg/g). Ingestion was the dominant exposure route. Non-carcinogenic risks were within acceptable limits, while carcinogenic risks surpassed 1.0 × 10^{- 6} for cadmium (Cd) and nickel (Ni). Cd risk was mainly ingestion-driven, whereas Ni posed the greatest concern through ingestion and dermal exposure. Lead (Pb) showed consistently low risk. Source identifications were analyzed using Pearson correlation, principal component analysis (PCA), and hierarchical cluster analysis (HCA), which grouped metals into three clusters, suggesting shared industrial origins. Positive matrix factorization (PMF) resolved five sources, four of which matched industrial sectors in pollutant release and transfer register (PRTR) data, including battery manufacturing, plastics, non-ferrous metal processing, and ceramics. Source 1, dominated by Cd, was not identified due to inventory gaps, but fenceline regression showed a strong correlation (R² = 0.983, p < 0.01) between Cd in ambient air and indoor settled dust, implicating emissions from a nearby steel facility.