Human health risk assessment (carcinogenic and non-carcinogenic) for heavy metals in groundwater: Case study of the Soummam Basin, Algeria

The contamination of groundwater by heavy metals poses a significant threat to public health, particularly in developing regions.This study evaluates the presence, sources, and health risks associated with six heavy metals (Pb, Cd, Cr, Ni, Zn, Fe) in 135 groundwater samples from the Soummam watershed, located in northeastern Algeria.A combination of multivariate analyses, pollution indices, and quantitative health risk assessment methods was used to identify contamination profiles and their implications.Principal component analysis revealed two major factors explaining 59.80% of the total variance.The first factor, dominated by Pb, Cd, Cr, Zn, and Fe, reflects a strong anthropogenic influence related to industrial discharges and urban pressures.The second factor, characterized by electrical conductivity, pH, and Ni, reflects geogenic processes, particularly the alteration or erosion of nickelrich geological formations, as well as localized contributions of agricultural origin (use of fertilizers containing nickel).Cluster analysis allowed the samples to be classified into two distinct groups: group 1 (66.67% of the samples), heavily contaminated with Pb and Cd, and group 2 (33.33% of the samples), showing moderate pollution dominated by Ni.The pollution indices (HEI and C deg ) confirmed this spatial heterogeneity in groundwater quality.The assessment of non-carcinogenic risks, based on HQ and HI indices for five age groups and three exposure pathways (ingestion, skin contact, inhalation), showed that ingestion is the most concerning pathway, while the other two present negligible risks.The assessment of carcinogenic risks revealed values exceeding the tolerable thresholds for all population groups.Finally, Monte Carlo simulations have reinforced these results, highlighting the persistence of significant health risks related to groundwater contamination in the studied region.These results highlight the need to implement appropriate management measures to ensure the protection of water resources and the health of exposed populations.