Hydrogen Sulfide

  • Hydrogen sulfide is a gas with a strong rotten egg odor.
  • Hydrogen sulfide is part of the natural environment, but it also can be released from industrial processes and landfills.
  • At low levels, hydrogen sulfide can be a nuisance and can cause symptoms associated with its foul odor.
  • There is limited information on the health effects of long-term exposure to hydrogen sulfide at low levels.

What is Hydrogen Sulfide?

Hydrogen sulfide is a colorless gas with a rotten egg odor. Hydrogen sulfide can be smelled at very low concentrations in air. Hydrogen sulfide is slightly heavier than air and can accumulate in enclosed, poorly ventilated, and low-lying areas.

Where Does Hydrogen Sulfide Come From?

Much of the hydrogen sulfide in the air comes from natural sources. It is produced when bacteria break down plant and animal material. This often happens in stagnant waters with low oxygen content, such as bogs and swamps. Hot springs and volcanoes are other natural sources of hydrogen sulfide.

Hydrogen sulfide can also be produced from human, agricultural, and industrial activities. Landfills, sewers, septic systems, wastewater treatment plants, animal manure, field fertilizers, and concentrated animal feeding operations are all sources of hydrogen sulfide. Industrial processes that release hydrogen sulfide include petroleum and natural gas extraction and refining, pulp and paper manufacturing, rayon textile production, and chemical manufacturing.

Landfills are a common source of hydrogen sulfide which can particularly affect nearby communities. Construction and demolition debris in a landfill often contains wallboard (gypsum); large amounts of hydrogen sulfide can be produced as it degrades. Production of hydrogen sulfide from wallboard is greatest when the wallboard is finely crushed and there is little oxygen, such as when the debris is buried or soaked with water.

What Happens to Hydrogen Sulfide in the Environment?

Hydrogen sulfide breaks down in the air and goes away if there is no ongoing source. It is converted to sulfur dioxide, then sulfates that are absorbed into plants and soil or removed through precipitation, such as rain or snow. This process takes 1-2 days in warm weather or up to several weeks in cold weather since colder temperatures allow hydrogen sulfide and its breakdown products to remain in outdoor air longer.

How Can I be Exposed to Hydrogen Sulfide?

Most people are exposed to low levels of hydrogen sulfide that occur naturally. People can also be exposed if they breathe air contaminated with hydrogen sulfide that is produced from a significant source, such as a swamp or a landfill.

What Happens to Hydrogen Sulfide Once It Is In My Body?

Once absorbed through the lungs, hydrogen sulfide does not accumulate in the body because it is rapidly metabolized (changed) in the liver and then excreted in the urine.

How Can Hydrogen Sulfide Affect my Health?

Exposure to high levels of hydrogen sulfide can result in health effects ranging from mild discomfort to more serious symptoms. Because the odor is so strong and offensive, hydrogen sulfide can be a nuisance at low levels and can cause symptoms that might be expected from a foul odor, such as nausea or headaches. People can have different sensitivities to hydrogen sulfide odors; some might experience symptoms while others are unaffected. People who have been exposed to hydrogen sulfide also report symptoms such as burning and tearing of eyes, coughing, and shortness of breath. If hydrogen sulfide levels increase or exposure occurs for many days or weeks, people can have more severe eye and respiratory irritation, as well as headaches, dizziness, nausea, and vomiting. Exposure to hydrogen sulfide may also worsen asthma symptoms. Most of the health effects caused by hydrogen sulfide typically diminish once people get to fresh air, or the source of the hydrogen sulfide is removed.

There is limited information on the health effects of long-term (months to years) exposure to low levels of hydrogen sulfide. This could result from living near water treatment plants, landfills, or other facilities that release the gas. Studies have reported higher incidences of eye irritation, cough, headache, nasal blockage, and impaired neurological function in people living near industries that emit hydrogen sulfide compared to people who do not live near such industries. (Neurological function impairment may be affect reaction time, balance, color discrimination, short-term memory, and mood) A limitation of these studies is that the people may have had exposure to other chemicals that could also have contributed to some of the observed health effects.

How Can I Reduce My Exposure?

If you smell strong hydrogen sulfide odors you can reduce your exposure by:

  • Avoiding areas that have known sources of hydrogen sulfide.
  • Keeping windows closed when outdoor odors are noticeable, or if the source is indoors, increasing ventilation to outdoor air.
  • Avoiding outdoor exercise when the smell is present.
  • Report the odor issue to the New York State Department of Environmental Conservation hotline below.

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