Hydrogen sulphide
Environmental Sources
Hydrogen sulphide 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. Hydrogen
sulphide can also result from industrial activities, such as food processing,
coke ovens, paper mills, tanneries, and petroleum refineries. It is released
primarily as a gas and will spread in the air and may remain in the air
for about 18 hours. When released as a gas, it will form sulphur dioxide
and sulphuric acid in the atmosphere.
Hydrogen sulphide is a colourless, flammable gas under normal conditions.
It is commonly known as stink damp, and sewer gas because it smells like
rotten eggs. People can smell it at low levels.
Human Health effects
Hydrogen sulphide is considered a broad-spectrum poison, meaning it can poison
several different systems in the body. Breathing very high levels of hydrogen
sulphide can cause death within just a few breaths. There could be loss
of consciousness after one or more breaths.
Exposure to lower concentrations can result in eye irritation, a sore throat
and cough, shortness of breath, and fluid in the lungs. These symptoms
usually go away in a few weeks. Long-term, low-level exposure may result
in fatigue, loss of appetite, headaches, irritability, poor memory, and
dizziness. Hydrogen sulphide has not been shown to cause cancer in humans.
Exposure limits
- The US EPA has established that hydrogen sulphide is a regulated toxic
substance and is a hazardous substance as defined under the Federal Water
Pollution Control Act.
- The US Occupational Safety and Health Administration (OSHA) has established
an acceptable ceiling concentration of 20 parts per million (20 ppm) in
the workplace, with a maximum level of 50 ppm allowed for 10 minutes if
no other measurable exposure occurs.
- The US National Institute for Occupational Safety and Health (NIOSH)
recommends a maximum exposure level of 10 ppm.
Sources & Links:
www.atsdr.cdc.gov/tfacts114.html
www.agius.com/hew/resource/h2s.htm
www.gulf.ca/ehs/msds/msds_condensate_sour.html
www.aquatreatment.ie/inindex.htm
www.mfe.govt.nz/monitoring/epi/air_quality/aqwork2.htm
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