The Palawan Quicksilver Mine (PQM), Philippines, is located on Palawan Island near several villages where approximately 2,000 residents live, and within about 3 km of important regional fisheries and recreational areas in Honda Bay. From 1953 to 1976, the PQM produced about 2,900 t of Hg, a moderate sized Hg mine on an international scale. More than 2,000,000 t of mine-waste calcines (roasted ore) was generated during mining and about half of this waste was dumped into Honda Bay to construct a jetty, which was used as a mining port . Since 1995, high Hg levels have been observed in 21 people living near the mine, who also experienced symptoms of Hg poisoning and were subsequently detoxified with chelating drugs. Mercury is a heavy metal of environmental concern because elevated concentrations are toxic to all living organisms. Mercury is one of the few pollutants where ingestion of contaminated food (primarily fish) has led to human deaths. Mine-waste calcines can be especially hazardous because they contain highly elevated Hg concentrations and soluble Hg salts and Hgo, which under certain conditions, can oxidize to Hg(II) and subsequently transform into methyl-Hg (CH3Hg+) through microbial processes, primarily by the action of sulfate reducing bacteria. Methyl-Hg is highly toxic, water soluble, and can biologically magnify with increasing trophic position in the food chain. Mercury contamination of fish and seafood is a common problem worldwide that can lead to Hg exposure to humans consuming such food sources. Mercury contaminated sediment and water from the PQM are potentially hazardous to residents and wildlife when they enter local surface water and food webs, especially in Honda Bay. To evaluate Hg contamination and Hg methylation in this area, total Hg and methyl-Hg concentrations were measured in mine wastes and mine water from the PQM, stream sediment and water from a pit lake and a local stream (Tagburos Creek), mine-waste calcines and water in Honda Bay, and water from local domestic wells. In and around the PQM, several adverse factors have contributed to local environmental Hg contamination, one of the most unfortunate was the placement of Hg-rich mine wastes into Honda Bay. Much of the methyl-Hg generated in the PQM calcines or in Honda Bay is transferred to water, and then to higher trophic levels such as marine fish and seafood that are human food sources. The PQM is a unique example of significant methyl-Hg formation near a Hg mine, Hg contamination of local marine seafood, and subsequent uptake of high levels of methyl-Hg by local residents consuming such seafood.
Biochemical-analysis; Biochemistry; Biohazards; Biological-effects; Biological-systems; Chemical-deposition; Chemical-hypersensitivity; Dose-response; Environmental-contamination; Environmental-exposure; Environmental-factors; Environmental-hazards; Environmental-pollution; Epidemiology; Exposure-assessment; Exposure-levels; Exposure-methods; Families; Fishing-industry; Mine-workers; Mining-industry; Poisons; Pollution; Quantitative-analysis; Risk-analysis; Statistical-analysis; Toxic-effects; Toxicology; Toxicopathology; Waste-disposal