This study was carried out to evaluate the heavy metals (Lead (Pb), Nickel (Ni), Chromium (Cr), Copper (Cu), Cadmium (Cd) and Zinc (Zn)) pollution in the Noyyal River of South India by collecting 130 river water samples (65 each in pre- and post-monsoon). The heavy metals were measured using Atomic Absorption Spectrophotometer (AAS). The data were used to calculate the associated health hazards for the inhabitants consume river water. Correlation analyses and average concentration of heavy metals denoted that post-monsoon metal concentrations were lesser compared to the pre-monsoon due to dilution effect. Modified Contamination Degree (MCD) indicated that 45% of pre-monsoon and 25% of post-monsoon samples were classified under extremely polluted category. Heavy metal pollution index (HPI) showed that all the regions fall under highly polluted category except ‘Region I′ where 20% of samples were under safe category during the pre-monsoon, whereas 9%,28%, 17% and 26% of samples in Regions I, II, III and IV were highly polluted during the post-monsoon season, respectively. Ecological Risk Index (ERI) revealed that high risks attained in Regions II (78%) and III (82%) during pre-monsoon, and reduced risks found in Regions II (28%) and III (45%) during post-monsoon season due to dilution by monsoon rainfall. Non-carcinogenic risks as inferred by the Hazard Index (HI) indicated that 78% and 52% of samples for infants, 75% and 49% of samples for teens and 71% and 45% of samples for adults exceeded the threshold limits of USEPA (HI > 1) and possessed risks during pre- and post-monsoon, respectively. The cancer risk assessment based on ingestion of heavy metals indicated that the order of risk is Ni > Cr > Cu. The HI for infants and teens was notably high to that of adults in both the seasons. This study will be useful to develop effective strategies for improving river water quality and to reduce human health hazards.

本研究旨在评估南印度 Noyyal 河中的重金属（铅 (Pb)、镍 (Ni)、铬 (Cr)、铜 (Cu)、镉 (Cd) 和锌 (Zn)）污染情况。收集 130 个河水样本（季风前后各 65 个）。使用原子吸收分光光度计（AAS）测量重金属。这些数据用于计算居民饮用河水的相关健康危害。相关性分析和重金属平均浓度表明，由于稀释效应，季风后金属浓度低于季风前。修正污染度 (MCD) 表明 45% 的季风前样本和 25% 的季风后样本被归类为极度污染类别。重金属污染指数 (HPI) 显示，除“I 区”外，所有地区都属于重污染类别，其中 20% 的样本在季风前处于安全类别，而 9%、28%、17% 和 26% 的样本在I、II、III 和 IV 区的样本分别在季风后季节受到高度污染。生态风险指数 (ERI) 显示，季风前二区 (78%) 和三区 (82%) 的风险较高，季风后二区 (28%) 和三区 (45%) 的风险降低由于季风降雨的稀释而形成的季节。危险指数 (HI) 推断的非致癌风险表明，78% 和 52% 的婴儿样本、75% 和 49% 的青少年样本以及 71% 和 45% 的成人样本超过了 USEPA 的阈值限制(HI > 1) 并且分别在季风前和季风后具有风险。基于摄入重金属的癌症风险评估表明，风险的顺序是 Ni > Cr > Cu。在这两个季节，婴儿和青少年的 HI 明显高于成人。这项研究将有助于制定改善河流水质和减少人类健康危害的有效策略。