Source apportionment and non-carcinogenic health risk assessment of selected heavy metals in the Turag river area of Gazipur District, Bangladesh

INTRODUCTION: Rapid industrialization in Bangladesh, especially in Gazipur District, has raised concern over heavy metal contamination of soil and water and the associated health risks to nearby residents. This study compared the concentration, spatial distribution, probable sources, and non-carcinogenic health risk of five heavy metals (Hg, Ni, Mn, Zn, and Co) in soil and water in the Turag River areas in Gazipur District. METHODS: Soil and water samples were collected from 18 sites in the Turag River (including both industrial and non-industrial zones) and analyzed for five heavy metal concentrations (Hg, Ni, Mn, Zn, and Co) using inductively coupled plasma-mass spectrometry (ICP-MS). Statistical analyses included principal component analysis (PCA), hierarchical cluster analysis (HCA), and Pearson correlation analysis, while non-carcinogenic human health risks were evaluated using the USEPA-based chronic daily intake (CDI), hazard quotient (HQ), and hazard index (HI) models for both adults and children. RESULTS: Mean soil metal concentrations followed the order Mn > Zn > Ni > Co > Hg in both zones, with markedly higher and more spatially concentrated Ni and Zn levels in the industrial zone near the Turag River areas. Spatial mapping, PCA, HCA, and correlation analyses consistently suggested a common anthropogenic influence on soil and water contamination in the industrial zone, with the strongest spatial concentrations observed near its northern boundary, compared with patterns consistent with multiple diffuse influences in the non-industrial zone. The modeled soil CDI values were generally higher for children than adults. Soil-based screening estimates indicated potential non-carcinogenic concern for children, including an Ni HQ of 1.66 in the industrial zone and cumulative hazard index values above the screening benchmark of 1 for children in both the industrial (HI = 2.32) and non-industrial (HI = 1.31) zones, while all modeled HQ and HI values for water remained below the screening benchmark of 1. CONCLUSION: These soil-based screening estimates suggest potential non-carcinogenic concern for children, particularly regarding Ni in the industrial zone, but are based on the < 0.5 mm fraction of soil collected at 15-20 cm depth and may not represent actual exposure to ground-surface soil or airborne particles. The study highlighted the need for targeted control of potential industrial sources and child-focused environmental health monitoring in industrializing peri-urban districts of Bangladesh.