The Hg-methylating ability of dissimilatory iron-reducing bacteria in the genera Geobacter, Desulfuromonas, and Shewanella was examined. All of the Geobacter and Desulfuromonas strains tested methylated mercury while reducing Fe(III), nitrate, or fumarate. In contrast, none of the Shewanella strains produced methylmercury at higher levels than abiotic controls under similar culture conditions. Geobacter and Desulfuromonas are closely related to known Hg-methylating sulfate-reducing bacteria within the Deltaproteobacteria.

Fugitive dust from the Red Dog Mine is a potential source of exposure to heavy metals for residents of the surrounding area. Possible pathways of exposure include direct inhalation of particles, dermal contact with or ingestion of contaminated soils, residential exposure of individuals who have close association with mine workers, and subsistence activities. Study results indicate that soils and mosses close to the haul road are contaminated with dust and metals from hauling activities. However, investigations of exposure from subsistence activities performed near Red Dog Mine do not indicate that human health has been negatively affected by metal contamination. Epidemiological studies of nearby village residents do not show blood lead levels that exceed the CDC level of concern for children. The mine currently uses several control practices to reduce dust and control human dust and metal exposure. Nonetheless, the potential for human health impairment will persist throughout the life of the mine and beyond. Sound environmental management and monitoring of human health should remain a priority for the Red Dog Mine and for agencies that provide regulatory oversight to the mine.