Children Face Higher Risk from Metal Contamination in River Waters

Children face significantly higher cumulative non-carcinogenic risk than adults when exposed to trace metal contamination in river waters, according to a new study carried out with water samples from the Betwa–Yamuna confluence in Bundelkhand in Uttar Pradesh.

Traditionally, scientists test water, calculate an average contamination level, and compare it to safety limits. However, this system of investigation has its limitations, as risk can vary with exposure level and the affected population.

An earlier study last year had demonstrated that surficial sediments of the Ganga plain act as major sinks of contamination and secondary sources of toxic metals, with clear spatial variability linked to anthropogenic inputs and geomorphic controls.

It showed strong coupling between sediment geochemistry and riverine metal transport, emphasising that contaminants stored in sediments can be remobilised into the water column under changing hydrological conditions, thereby posing risks to aquatic systems and human populations.

Building on these findings, and recognising that rivers in the Ganga Plain are extensively used for domestic and agricultural purposes despite increasing pollution pressures, scientists extended the investigation beyond sediment contamination alone to evaluate the direct implications for water quality and human health.

Scientists from Birbal Sahni Institute of Palaeosciences (BSIP), Lucknow, an autonomous institution of the Department of Science and Technology (DST), focused on assessing dissolved metal contamination in river waters and associated human health risks  

Surface water samples were collected periodically from strategically selected locations in the Betwa–Yamuna confluence to capture spatial and seasonal variability, followed by standardised laboratory measurements of physicochemical parameters and trace metal concentrations.

Subsequently, quantitative risk assessment models were applied to estimate exposure levels and evaluate potential non-carcinogenic and carcinogenic risks using internationally accepted frameworks.

Using a technique called Monte Carlo simulation, the researchers ran 10,000 virtual scenarios simulating human exposure to metals such as arsenic, lead, and cadmium.

Each simulation tweaked variables such as how much water people drink, their body weight, and seasonal changes in pollution, covering a range of possibilities, enabling probabilistic characterisation of risk distributions and threshold exceedance probabilities.

This ensured robust data generation, reliable interpretation, and scientifically sound conclusions, thereby improving environmental monitoring and risk assessment.

The study published in Nature Scientific Reports showed that children face a significantly higher cumulative non-carcinogenic risk, with hazard index (HI, a measure of hazard probability) exceeding safety thresholds in approximately 67% of simulated scenarios, and that arsenic exposure poses a substantial carcinogenic risk under realistic exposure variability.

This integrated, uncertainty-aware approach establishes a new method for river health assessment in developing regions and delivers a robust scientific foundation for targeted mitigation, exposure management, and evidence-based water safety policy.

These results point to a combination of natural and anthropogenic (Human-related) inputs, such as agricultural runoff, untreated effluents and industrial discharges, thermal power generation, and urban sewage. Besides, it highlights chronic pollution risks that, if untreated, could compromise drinking water safety.

The amplified contaminant levels and health risks at the confluence are consistent with cumulative upstream loading and hydraulic mixing of two chemically contrasting river systems, which increases both metal mobilisation and exposure potential.

The study indicates the need for priority control of heavy metals at the Betwa–Yamuna confluence and can help develop effective mitigation and management strategies.