Mercury Contamination in Water and Sediments and the Associated Health Risk: A Case Study of Artisanal Gold-mining

This study investigated mercury (Hg) contamination in the Gilgit-Baltistan, Pakistan. Water and sediment samples were collected from various sites having artisanal gold-mining along the Indus, Gilgit, and Hunza Rivers. Sediments were classified as wet sediment (WS, collected just after amalgamation), fresh dry sediment (FDS, collected after 1–2 h of amalgamation), and old dried sediment (ODS, collected after 1–2 days of amalgamation). Samples were analyzed for Hg by atomic absorption spectrophotometry with a mercury hydride system. Mercury mean concentrations were 2767 mg/kg in WS, 1917 mg/kg in FDS, and 191 mg/kg in ODS. These results revealed very high levels of Hg contamination in the WS and FDS. The Hg contamination of the spring (drinking water) did not exceed the permissible limits set by the World Health Organization (WHO) and Pakistan’s environmental protection agency (Pak-EPA); however, the stream water surpassed these limits. Therefore, the Hg levels in the drinking water was used to assess the potential human health risk via the average daily dose (ADD) and hazard quotient (HQ). The ADD values were 0.03 and 0.06 µg/kg-day and HQ value of 0.9 and 2.0 for adults and children, respectively. This level of Hg contamination level is alarming and could be hazardous in future.