Comparative analysis of metal contaminants and environmentally persistent free radicals in indoor dust from urban and rural households

Abstract

Indoor dust is recognized as a reservoir of chemical toxicants owing to its high surface area and propensity for contact transfer and resuspension. It is an indicator of indoor pollutants and a potential source for exposure from ingestion and inhalation. To identify health-risks, house dust samples collected from urban (New York City, NY) and rural (West Lafayette, IN) residences were analyzed for two toxicant classes – toxic metals and environmentally persistent free radicals (EPFRs). Elemental composition and concentrations were quantified by X-ray fluorescence (XRF) spectroscopy and inductively coupled plasma-mass spectrometry (ICP-MS). Higher levels of crustal mineral elements (Na, Al, Si, Mg, P, S, Cl, K, Ca, Ti, Fe, and Mn) were observed in the rural dust samples (typically 2–5× higher in concentration), whereas several toxic metals were concentrated in the urban dust samples (Zn ≈ 430 ppm_m, Pb ≈ 100 ppm_m, Cu ≈ 70 ppm_m), corresponding to 2–3× higher concentrations. Analysis of elemental enrichment factors (EFs) indicated enhancement of several industrially relevant metals. Geospatial autocorrelation using Moran's Index revealed significant spatial clustering of several toxicologically relevant elements in the rural area, whereas most toxic elements in the urban area were randomly distributed, consistent with distinct source profiles. EPFR type and abundance were evaluated by electron paramagnetic resonance spectroscopy. Despite overlapping signals, several source-consistent components were identified through comparison with previous studies. The EPFR concentrations in these house dust samples spanned a wide range of 10⁹–10¹⁶ radicals µg⁻¹ dust. This systematic screening framework enables source apportionment of indoor dust contaminants and supports evaluation of potential health impacts.