Benzene
Environmental
Sources
Benzene is a colourless liquid with a sweet odour.
It evaporates into the air very quickly and dissolves slightly in water.
It is highly flammable and is formed from both natural processes and human
activities. It is a volatile organic compound.
Industrial processes (such as oil refineries) are the main source of benzene
in the environment. Benzene vapours from industrial process (e.g. oil
refineries) are released into the atmosphere as from leaking fuel pipes
(fugitive emissions).
Benzene is found in many commercial solvents and is used
to make other chemicals which are used to make plastics, resins, and nylon
and synthetic fibres. Benzene is also used to make some types of rubbers,
lubricants, dyes, detergents, drugs, and pesticides. Natural sources of
benzene include volcanoes and forest fires. Benzene is also a natural
part of crude oil, gasoline, and cigarette smoke.
Human Health
Effects
Benzene is a known human carcinogen. Long-term (365 days or longer) exposure
to high levels of benzene in the air can cause leukaemia, cancer of the
blood-forming organs. Benzene causes harmful effects on the bone marrow
and can cause a decrease in red blood cells leading to anaemia. It can
also cause excessive bleeding and can affect the immune system, increasing
the chance for infection.
Breathing very high levels of benzene can result in death, while high levels
can cause drowsiness, dizziness, rapid heart rate, headaches, tremors,
confusion, and unconsciousness. Eating or drinking foods containing high
levels of benzene can cause vomiting, irritation of the stomach, dizziness,
sleepiness, convulsions, rapid heart rate, and death. Central nervous
system depression results in decreased alertness, headaches, sleepiness,
loss of consciousness. Defatting of the dermatitis is also an effect of
benzene
Some women who breathed high levels of benzene for many months had irregular
menstrual periods and a decrease in the size of their ovaries. It is not
known whether benzene exposure affects the developing foetus in pregnant
women or fertility in men.
Exposure limits
- The Bay Area Air Quality Management
District in San Francisco, USA documented a background concentration level
of 1.0 ppb for benzene for the whole bay area in San Francisco.
- The US EPA has set the maximum permissible
level of benzene in drinking water at 0.005 milligrams per litre (0.005
mg/L).
- The US EPA requires that spills or accidental
releases into the environment of 10 pounds or more of benzene be reported
to the EPA.
- The US Occupational Safety and Health
Administration has set a limit of 200 parts benzene per billion of workplace
air (100 ppb) TWA and a 500 mg/m3 STEL.
- The ACGIH (American Conference of Governmental
Industrial Hygienist) has TWA for skin contact with benzene of 250 ppb.
- The US NIOSH (National Institute for
Occupational Safety and Health) has a benzene limit of 3000 ppm.
- According to the World Health Organization
(WHO), benzene is a known carcinogen and an ambient air concentration
of between 5 to 20 mg/m3 is allowed.
Links and sources:
www.epa.gov/oerrpage/superfund/programs/er/hazsubs/sources.htm
www.atsdr.cdc.gov/tfacts3.html
www.who.int/environmental_information/Air/Guidelines/Chapter3.htm#3.1
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