HYDROGEN SULFIDE 

CAS # 7783-06-4 

Division of Toxicology and Environmental Medicine ToxFAQsTM July 2006 

This fact sheet answers the most frequently asked health questions (FAQs) about hydrogen sulfide. 

For more information, call the ATSDR Information Center at 1-888-422-8737. This fact sheet is one in 

a series of summaries about hazardous substances and their health effects. It is important you 

understand this information because this substance may harm you. The effects of exposure to any 

hazardous substance depend on the dose, the duration, how you are exposed, personal traits and 

habits, and whether other chemicals are present. 

HIGHLIGHTS: Hydrogen sulfide occurs naturally and is also produced by human 

activities. Just a few breaths of air containing high levels of hydrogen sulfide gas 

can cause death. Lower, longer-term exposure can cause eye irritation, headache, 

and fatigue. Hydrogen sulfide has been found in at least 35 of the 1,689 National 

Priorities List sites identified by the U.S. Environmental Protection Agency (EPA). 

What is hydrogen sulfide? 

Hydrogen sulfide (H2S) occurs naturally in crude petroleum, 

natural gas, volcanic gases, and hot springs. It can also result 

from bacterial breakdown of organic matter. It is also produced 

by human and animal wastes. Bacteria found in your mouth and 

gastrointestinal tract produce hydrogen sulfide from bacteria 

decomposing materials that contain vegetable or animal proteins. 

Hydrogen sulfide can also result from industrial activities, such 

as food processing, coke ovens, kraft paper mills, tanneries, and 

petroleum refineries. 

Hydrogen sulfide is a flammable, colorless gas with a 

characteristic odor of rotten eggs. It is commonly known as 

hydrosulfuric acid, sewer gas, and stink damp. People can smell 

it at low levels. 

What happens to hydrogen sulfide when it enters 

the environment? 

‘ Hydrogen sulfide is released primarily as a gas and spreads 

in the air. 

‘ Hydrogen sulfide remains in the atmosphere for about 18 

hours. 

‘ When released as a gas, it will change into sulfur dioxide and 

sulfuric acid. 

‘ In some instances, it may be released as a liquid waste from 

an industrial facility. 

How might I be exposed to hydrogen sulfide? 

‘ You may be exposed to hydrogen sulfide from breathing 

contaminated air or drinking contaminated water. 

‘ Individuals living near a wastewater treatment plant, a gas 

and oil drilling operation, a farm with manure storage or livestock 

confinement facilities, or a landfill may be exposed to higher 

levels of hydrogen sulfide.

 ‘ You can be exposed at work if you work in the rayon textiles, 

petroleum and natural gas drilling and refining, or wastewater 

treatment industries. Workers on farms with manure storage 

pits or landfills can be exposed to higher levels of hydrogen 

sulfide. 

‘ A small amount of hydrogen sulfide is produced by bacteria 

in your mouth and gastrointestinal tract. 

How can hydrogen sulfide affect my health? 

Exposure to low concentrations of hydrogen sulfide may cause 

irritation to the eyes, nose, or throat. It may also cause difficulty 

in breathing for some asthmatics. Brief exposures to high 

concentrations of hydrogen sulfide (greater than 500 ppm) can 

cause a loss of consciousness and possibly death. In most 

cases, the person appears to regain consciousness without any 

other effects. However, in many individuals, there may be 

permanent or long-term effects such as headaches, poor attention 

span, poor memory, and poor motor function. No health effects 

have been found in humans exposed to typical environmental 

concentrations of hydrogen sulfide (0.00011–0.00033 ppm). 

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES, Public Health Service 

Agency for Toxic Substances and Disease Registry 
 

 

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ToxFAQsTM Internet address is http://www.atsdr.cdc.gov/toxfaq.html 

Where can I get more information? For more information, contact the Agency for Toxic Substances and Disease 

Registry, Division of Toxicology and Environmental Medicine, 1600 Clifton Road NE, Mailstop F-32, Atlanta, GA 30333. Phone: 

1-888-422-8737, FAX: 770-488-4178. ToxFAQs Internet address via WWW is http://www.atsdr.cdc.gov/toxfaq.html. ATSDR 

can tell you where to find occupational and environmental health clinics. Their specialists can recognize, evaluate, and treat 

illnesses resulting from exposure to hazardous substances. You can also contact your community or state health or environmental 

quality department if you have any more questions or concerns. 

Scientists have no reports of people poisoned by ingesting 

hydrogen sulfide. Pigs that ate feed containing hydrogen sulfide 

experienced diarrhea for a few days and lost weight after about 

105 days. 

Scientists have little information about what happens when you 

are exposed to hydrogen sulfide by getting it on your skin, 

although they know that care must be taken with the compressed 

liquefied product to avoid frost bite. 

How likely is hydrogen sulfide to cause cancer? 

Hydrogen sulfide has not been shown to cause cancer in humans, 

and its possible ability to cause cancer in animals has not been 

studied thoroughly. The Department of Health and Human 

Services (DHHS), the International Agency for Research on 

Cancer (IARC), and the EPA have not classified hydrogen sulfide 

for carcinogenicity. 

How can hydrogen sulfide affect children? 

Children are likely to be exposed to hydrogen sulfide in the same 

manner as adults, except for adults at work. However, because 

hydrogen sulfide is heavier than air and because children are 

shorter than adults, children sometimes are exposed to more 

hydrogen sulfide than adults. Health problems in children who 

have been exposed to hydrogen sulfide have not been studied 

much. Exposed children probably will experience effects similar 

to those experienced by exposed adults. Whether children are 

more sensitive to hydrogen sulfide than adults or whether 

hydrogen sulfide causes birth defects in people is not known. 

How can families reduce the risk of exposure to 

hydrogen sulfide? 

Families can be exposed if they live near natural or industrial 

sources of hydrogen sulfide, such as hot springs, manure holding 

tanks, or pulp and paper mills. Families may want to restrict 

visits to these places. 

Is there a medical test to show whether I’ve been 

exposed to hydrogen sulfide? 

Hydrogen sulfide can be measured in exhaled air, but samples 

must be taken within 2 hours after exposure to be useful. A more 

reliable test to determine if you have been exposed to hydrogen 

sulfide is the measurement of thiosulfate levels in urine. This 

test must be done within 12 hours of exposure. Both tests require 

special equipment, which is not routinely available in a doctor’s 

office. Samples can be sent to a special laboratory for the tests. 

These tests can tell whether you have been exposed to hydrogen 

sulfide, but they can not determine exactly how much hydrogen 

sulfide you have been exposed to or whether harmful effects will 

occur. 

Has the federal government made recommendations 

to protect human health? 

The Occupational Safety and Health Administration (OSHA) has 

set an acceptable ceiling limit for hydrogen sulfide of 20 parts 

hydrogen sulfide per 1 million parts of air (20 ppm) in the 

workplace. 

The National Institute for Occupational Safety and Health 

(NIOSH) recommends a 10-minute ceiling limit of 10 ppm in the 

workplace. 

Reference 

Agency for Toxic Substances and Disease Registry (ATSDR). 

2006. Toxicological Profile for Hydrogen Sulfide (Update). 

Atlanta, GA: U.S. Department of Health and Human Services, 

Public Health Service. 

HYDROGEN SULFIDE 

CAS # 7783-06-4