Odors in Conimicut: Hydrogen Sulfide (H2S) Background Info

Hydrogen sulfide is a gas with a foul odor of rotten eggs.

• Some individuals are sensitive to odors of hydrogen sulfide at levels of just a few parts per billion (ppb).
• Most people find hydrogen sulfide odors objectionable at 10 ppb, the RI DEM secondary standard.
• The odor of hydrogen sulfide can be nauseating, causing those exposed to feel sick to their stomachs.

Communities impacted by hydrogen sulfide are primarily affected by its foul odor.

• Although high levels of hydrogen sulfide can be irritating and cause a variety of health effects, irritation and respiratory effects are not excepted to occur at levels below 30 ppb, the Minimum Risk Level established by the US Agency for Toxic Substances and Disease Registry.
• Some individuals are extremely sensitive to the odors of hydrogen sulfide. Health effects associated with individual sensitivity to odors are relieved once the individuals leave the area affected by the odors.
• Occupational standards for hydrogen sulfide of 10,000 ppb are not appropriate for evaluating community exposures.

Environmental levels of hydrogen sulfide are normally quite low.

• Hydrogen sulfide is produced during the decay of sewage, garbage, or other material. Normally, only very small amounts are present in the air.
• In Rhode Island, communities adjacent to landfills, sewage treatment plants and composting facilities have been impacted by hydrogen sulfide.
• Hydrogen sulfide levels in air usually decline within a day, once sources have been removed.