Human Health Risk Assessment of Heavy Metal Contaminated Groundwater: Implications for Drinking Water Treatment and Policy Design

Abstract

Groundwater provides drinking water to billions of people around the world. However, in many areas, the resource is quietly poisoned. Heavy metals such as arsenic (As), lead (Pb), cadmium (Cd), chromium (Cr), and mercury (Hg) enter water bodies through natural geological weather, mining operations, industrial emissions, and unregulated agricultural inputs. The consequences are severe and often irreversible. This paper provides a systematic assessment of the human health risks (HHRA) of groundwater contaminated with heavy metals, using the U.S. Environmental Protection Agency's (USEPA) four-step framework as a methodology. We evaluate carcinogenic and non-carcinogenic risks through food, urine absorption, and respiratory tracts. Based on field studies and experimental datasets from South Asia, Sub-Saharan Africa, and Southeast Asia, the analysis shows that hazard ratio (HQ) and cancer risk (CR) values in affected communities are routinely above acceptable ranges. We evaluate the performance of traditional and modern drinking water treatment techniques such as freezing, absorption, membrane filtration, and electrocogulation, especially in terms of extraction efficiency, cost, and contextual application. Finally, we examine the governance landscape related to groundwater quality and identify critical gaps in monitoring, regulation, and justice. Six evidence-based policy recommendations have been made to bridge the gap between scientific knowledge and preventive measures. The findings confirm that heavy metal contamination in drinking water is not just a technical challenge but a profound structural and ethical challenge, requiring an urgent and coordinated response from governments, engineers, scientists, and communities.