Assessment of mercury contamination and human exposure associated with coastal disposal of waste from a cinnabar mining operation, Palawan, Philippines

An integrated geochemical and toxicological assessment of environmental mer cury contamination and attendant human exposure in Honda Bay, Palawan was u ndertaken in 1995 following a nationally reported pollution scare centered on a coastal jetty, Sitio Honda Bay, constructed using approximately 1 mill ion tons of tailings and beneficiation waste from a cinnabar mine. Mercury (Hg) data for marine and fluvial sediments, fish tissues and human hair ind icate that the toxicological hazard is considerably lower than initially re ported by state environment and health officials. Typical Hg concentrations in surficial Honda Bay sediments were found to lie within the global backg round range (<60 mu g/kg). Downcore profiles provide no evidence of enhance d Hg fluxes coincident with the onset of mining and/or coastal tailings dis posal. The mean and median Hg concentrations recorded in tissues of six spe cies of Honda Bay fish are compliant with thresholds established by the US Environmental Protection Agency (US-EPA) for marketable stocks. Earlier rep orts of 'Minamata range' Hg concentrations in fish and shellfish from Honda Bay remain unsubstantiated. Geochemical analyses of samples of the Sitio H onda Bay substrate have confirmed the prevalence of solid-phase Hg concentr ations to ca. 340 mg/kg. The speciation of Hg is, however, dominated by sec ondary oxides of low bioavailability. The mean Hg concentration in hair fro m Sitio Honda Bay residents (4.41 mg/kg) was found to be statistically anal ogous to that for a neighbouring coastal community unimpacted by the coasta l disposal of mine waste. A negligible residential exposure factor is thus inferred for the former. Relatively high hair Hg burdens prevail throughout the coastal Honda Bay population, consistent wit significant methyl Hg ing estion through daily fish consumption. The data presented provide no enviro nmental or toxicological justification for immediate remedial action.