HEAVY METAL CONTAMINATION (PB, CD, AS, AND CR) IN GROUNDWATER FROM NATURAL AND ANTHROPOGENIC SOURCES: A SYSTEMATIC REVIEW COMPARING CONCENTRATIONS WITH WORLD HEALTH ORGANIZATION WATER QUALITY STANDARD

Groundwater is a critical freshwater resource for domestic, agricultural, and industrial use; however, it is
increasingly threatened by heavy metal contamination. This systematic review evaluates contamination by Lead
(Pb), Cadmium (Cd), Arsenic (As), and Chromium (Cr) in groundwater from both natural and anthropogenic
sources and compares reported concentrations with World Health Organization (WHO) drinking water standards.
Using the PRISMA framework, peer-reviewed studies published between 2016 and 2026 were screened, with ten
studies meeting the inclusion criteria. The results show distinct spatial and metal-specific contamination patterns.
High contributions were observed in Bangladesh for Pb (~47%), Zimbabwe for Cd (~44%), India for As (~84%),
and the Philippines for Cr (~65%). These patterns reflect the influence of industrial activities, mining, waste
mismanagement, and geogenic processes. Arsenic and Chromium are strongly associated with carcinogenic risks,
while Lead and Cadmium primarily contribute to neurological and renal health effects. Most study sites reported
concentrations exceeding WHO limits, with Hazard Quotient (HQ > 1) and Incremental Lifetime Cancer Risk
(ILCR > 10⁻⁴) indicating significant health risks. The findings highlight substantial spatial variability driven by
geological conditions and human activities. Continuous monitoring, improved regulatory enforcement, and
targeted remediation strategies are essential to protect public health and ensure sustainable groundwater
management.