Carbon tetrachloride
Environmental Sources
Carbon tetrachloride is a manufactured compound that does not occur naturally.
It's a clear liquid with a sweet smell that can be detected at low levels.
It's also called carbon chloride, methane tetrachloride, perchloromethane,
tetrachloroethane, or benziform. Carbon tetrachloride is most often found
as a colourless gas. It's not flammable and doesn't dissolve in water very
easily. It was used in the production of refrigeration fluid and propellants
for aerosol cans, as a pesticide, as a cleaning fluid and degreasing agent,
in fire extinguishers, and in spot removers. Because of its harmful effects,
these uses are now banned and it is only used in some industrial processes.
Human Health effects
High exposure to carbon tetrachloride can cause liver, kidney, and central
nervous system damage. These effects result from either eating, drinking,
or breathing it, and possibly from exposure to the skin. The liver is
especially sensitive to carbon tetrachloride because it swells and cells
are damaged or destroyed. Kidneys are also damaged, causing a build up
of wastes in the blood. If exposure is low and then stops, the liver and
kidneys can repair the damaged cells and function normally again.
If exposure is very high, the nervous system, including the brain, is affected.
People may feel intoxicated and experience headaches, dizziness, sleepiness,
and nausea and vomiting. These effects may subside if exposure is stopped,
but in severe cases, coma and even death can occur. Carbon tetrachloride
may reasonably be anticipated to be a carcinogen as animals that ingested
carbon tetrachloride over a long time developed liver cancer.
Exposure limits
- The Bay Area Air Quality Management
District in San Francisco, USA documented a background concentration level
of 0.11 ppb for carbon Tetrachloride for the whole bay area in San Francisco.
- According to PollutionWatch
Canada, carbon tetrachloride accumulates to contribute to a global background
concentration, which is estimated to be between 0.69 and 0.94 µg/m3.
- The US Environmental Protection Agency
(EPA) has set a limit of 0.005 parts of carbon tetrachloride per million
parts of drinking water (0.005ppm). The EPA recommends that drinking water
exposures should not exceed 0.3 ppm for adults and 0.07 ppm for children
for long periods of time (7 years).
- The US EPA has also set limits on how
much carbon tetrachloride can be released from an industrial plant into
waste-water and is preparing to set limits on how much can be released
into outside air.
- The US Occupational Safety and Health
Administration (OSHA) set a maximum concentration limit in workplace air
of 10 ppm for an 8-hour workday over a 40-hour workweek.
Sources & links:
www.atsdr.cdc.gov/tfacts30.html
www.greenpeace.org/~toxics/reports/primex9april.pdf
www.osha-slc.gov/SLTC/pel/
www.jtbaker.com/msds/c0979.htm
www.scorecard.org/env-releases/def/hap_drivers.html#71-43-2
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