2. Relevance to Public Health 2.1 Background and Environmental Exposures to Hydrogen Sulfide and Carbonyl Sulfide in the United States

Hydrogen Sulfide. Hydrogen sulfide (H2S) is a colorless gas with a characteristic odor of rotten eggs. It naturally occurs in the gases from volcanoes, sulfur springs, undersea vents, swamps, stagnant bodies of water, and in crude petroleum and natural gas. Additionally, bacteria, fungi, and actinomycetes release hydrogen sulfide during the decomposition of sulfur-containing proteins and by the direct reduction of sulfate (SO4). Hydrogen sulfide is frequently encountered in various industries and may be released to the environment as a result of their operations. Some of these industries include natural gas production, municipal sewage pumping and treatment plants, landfilling, swine containment and manure handling, pulp and paper production, construction in wetlands, asphalt roofing, pelt processing, animal slaughter facilities, tanneries, petroleum refining, petrochemical synthesis, coke production plants, viscose rayon manufacture, sulfur production, iron smelting, and food processing.