Vol. 22, No. 2
Books and Publications
Publication from the World Health Organization
Carbon Tetrachloride, Environmental Health Criteria
1999, xviii + 177 pages (English with summaries in French and Spanish),
ISBN 92-4-157208-6, CHF 42.-/USD 37.80; In developing countries: CHF
29.40, Order No. 1160208.
This book evaluates the risks to human health and the environment posed
by exposure to carbon tetrachloride, a volatile liquid previously used
in the production of chlorofluorocarbons and other chlorinated hydrocarbons.
Production and use have declined considerably following the Montreal
Protocol on Substances that Deplete the Ozone Layer. Additional former
applications that have also been phased out include use as a grain fumigant,
pesticide, vent for oils and fats, metal degreaser, fire extinguisher,
and flame retardant.
A review of data on the environmental behavior of this volatile chemical
concludes that almost all carbon tetrachloride released to the environment
is ultimately present in the atmosphere. Although estimates of atmospheric
lifetime vary considerably, 45-50 years is accepted as the most reasonable
range. Studies indicate significant global transportation and ubiquitous
presence in air. The main degradation site is the stratosphere, where
the chemical is photolytically degraded by ultraviolet radiation. Abundant
evidence indicates that carbon tetrachloride contributes to both global
warming and ozone depletion.
Concerning sources of exposure, studies of concentrations detected
in a wide range of indoor and outdoor samples indicate that the general
population can be exposed to carbon tetrachloride via air, food, and
drinking-water. A review of studies of kinetics and metabolism in laboratory
animals and humans cites evidence that carbon tetrachloride is well
absorbed from the gastrointestinal and respiratory tracts and distributed
throughout the body, with the highest concentrations detected in the
liver, brain, kidney, muscle, fat, and blood.
A review of toxicity studies conducted in laboratory mammals and in
vitro test systems indicates that the liver and kidney are the principal
targets of toxic action. The severity of these toxic effects depends
on a number of factors, including diet. Studies show that other compounds,
including ethanol, can potentiate the hepatotoxicity of carbon tetrachloride.
Long-term toxicity studies were judged inadequate to assess the chemical's
carcinogenic potential. Carbon tetrachloride produced moderate irritation
following skin application in animals.
An assessment of health effects in humans draws on findings from studies
in human volunteers and case reports of accidental and suicidal poisoning.
These findings confirm toxic effects on the liver and kidney. Acute
symptoms of exposure include nausea, vomiting, headache, dizziness,
dyspnea, and death. Liver damage appears after 24 hours or more, while
kidney damage becomes evident only 2 to 3 weeks following acute exposure.
Studies indicate that hepatic and renal damage can arise from long-term
exposure to low concentrations. Available epidemiological studies have
failed to establish an association between exposure to carbon tetrachloride
and increased risk of mortality, neoplasia, or liver disease.
On the basis of this review, the report established a tolerable daily
intake for carbon tetrachloride of 1.42 mg/kg body weight, and a tolerable
daily concentration in air of 6.1 mg/m3.