VOLUME 19 (Supplement)

Radiological assessment of groundwater resources: Implications for public health and regulatory compliance

This study presents the first systematic radiological assessment of raw groundwater resources in Metro Manila, Philippines, establishing a baseline for public health protection and regulatory compliance. In response to increasing reliance on groundwater following drought-induced surface water shortages, 24 untreated groundwater samples were analyzed for gross alpha, gross beta, and dissolved ²²²Rn activity concentrations. Gross alpha activities were low (<0.04–0.18 Bq/L), remaining below the Philippine National Standards for Drinking Water (PNSDW) screening level of 0.5 Bq/L. In contrast, gross beta activities ranged from <0.2 to 1.8 Bq/L, with three wells exceeding the national screening level of 1.0 Bq/L. Dissolved 222Rn activities ranged from 2 to 140 Bq/L, with 19 samples exceeding the PNSDW screening level of 11 Bq/L and three exceeding the World Health Organization reference level of 100 Bq/L. Elevated gross beta and ²²²Rn activities were associated with the volcanic deposits of the Guadalupe Formation and longer groundwater residence times. Age-dependent dose assessment showed that ingestion was the dominant exposure pathway. Mean total annual effective doses (AED_tot) were 1.298, 0.801, and 0.727 mSv/y for infants, children, and adults, respectively, all exceeding the WHO individual dose criterion of 0.1 mSv/y. Mean excess lifetime cancer risks were 2.94 × 10⁻³ for females and 2.63 × 10⁻³ for males, exceeding the reported global average value of 1.45 × 10⁻³. These findings indicate a non-negligible radiological health risk from untreated groundwater consumption and underscore the need for routine radiological monitoring in groundwater management.