Heavy Metals in Indoor Dust Across China: Occurrence, Sources and Health Risk Assessment

In this study, the occurrence of heavy metals including cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb), and zinc (Zn) was investigated in indoor dust samples collected from 33 urban and rural areas in 11 provinces, China. The concentrations of the selected heavy metals were determined by an inductively coupled plasma mass spectrometry. The mean concentrations of Zn (166 mg kg^-1), Pb (40.7 mg kg^-1), Cr (19.8 mg kg^-1), Cu (16.9 mg kg^-1), and Cd (2.29 mg kg^-1) in indoor dust are in low or moderate levels compared with other countries or regions. Cd was significantly enriched with the highest enrichment factor of 23.7, followed by Zn, Pb, Cu, and Cr, which were all lower than 3. The concentrations of Pb from Northern China (61.4 mg kg^-1) were significantly higher than those from Southern China (8.88 mg kg^-1). The concentrations of heavy metals in indoor dusts from rural areas were higher than those from urban areas except for Cu. The multivariate analysis of variance revealed that wall cover, fuel types, and air conditioning were dominant factors influencing the levels of heavy metals in indoor dust. Principal component analysis showed that outdoor dust and wall paint were main factors for the high concentrations of Cd, Pb, and Cr, accounting for 40.6% of the total contribution; traffic sources contributed to the high levels of Cu and Zn explained 20.6% of the total variance. The hazard indexes of selected heavy metals were less than 1 and carcinogenic risk value of Cr were between 1.01 × 10^-6 and 1 × 10^-4, indicating minor noncarcinogenic and carcinogenic risks from heavy metals in indoor dust for residents in China. Pb contributed 72.0% and 86.9% to the sum of noncarcinogenic risk values of selected heavy metals for adults and children, respectively. The carcinogenic risk value of Cr was approximately 13-fold higher than that of Cd for both adults and children. Children endured higher risks from heavy metals in indoor dust compared with adults.