Pseudo-total metal loads in dusts and soils of the steel city and coal capital of India: source apportionment and assessment of human health and ecological risks

The study examined metal concentrations in indoor dust, street dust, and soils of Bokaro, known as the ‘Steel City,’ and Dhanbad, recognized as the ‘Coal Capital’ of India, across summer, monsoon, and winter seasons in 2019. In Bokaro, the highest concentrations (mg/kg) of metals including Al (7755.12), Mg (8525), Mn (370.26), Fe (27882.75), Cu (738.83), Cr (44.57), Ni (31.33), Pb (29.67), and Zn (683.42) were observed during winter, whereas in Dhanbad, higher concentrations were noted during summer and monsoon months. Among the metals, Zn concentrations exceeded the World Health Organisation permissible limit (50 mg/kg) in both cities across all seasons. During summer, monsoon, and winter, concentrations (mg/kg) in Bokaro were 77.07, 102.53, 683.42, and in Dhanbad were 139.69, 541.36, and 361.39, respectively. Indoor dust generally exhibited higher metal concentrations than street dust and soil, indicating either its indoor origin or accumulation over time. Moderate contaminations, according to geo-accumulation index values, were contributed by Cu (1.21–1.24), Pb (1.06–1.21), and Zn (1.07–1.80). Ecological risk indices were highest in Bokaro's street dust during summer (33.66 ± 27.27) and Dhanbad's soils during monsoons (46.06 ± 10.90), but no significant ecological danger detected. However, carcinogenic risks were evident for children in Dhanbad due to Cr, in both street dust (1.18E-06) and soils (1.25E-06) during summers. The principal component analysis identified the metals originating from mixed sources in different matrices and seasons. Seasonal variations in indoor dust, street dust, and soil demonstrated the dominance of anthropogenic activities, such as coal/metal mining and traffic load. Overall, the study underscores the necessity for ongoing monitoring and mitigation of anthropogenic environmental impacts to safeguard human health.