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The Wikipedia article on carbon tetrachloride portrays it as a dangerous chemical that is a known carcinogen and "potent" hepatogen.

I don't really understand this. In the old days carbon tetrachloride was widely used as dry cleaning fluid and many thousands of dry cleaning workers breathed carbon tetrachloride vapors literally all day long. If the Wikipedia article is to be believed all those people would have been dropping dead from liver failure or cancer, yet that did not happen. In fact, carbon tetrachloride was used in dry cleaners for decades, which obviously would not have happened if people were dropping dead left and right.

Is this just a case of scare mongering or is there some legitimate factual basis for not using carbon tetrachloride?

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Carbon tetrachloride (CCl4) is very toxic. It can cause both serious acute and chronic effects. The severity of effects depends on several factors such as:

  • dose
  • length of exposure
  • frequency of exposure
  • exposure route
  • other toxic substances present
  • factors related to the exposed person (age, weight, physiological susceptibility) etc.

CCl4 is toxic via all 3 routes of exposure (oral, dermal and inhalation) and can cause a range of detrimental effects, including (but not limited to):

Oral and inhalation exposure to high concentrations of carbon tetrachloride results in acute central nervous system effects including dizziness, vertigo, headache, depression, confusion, incoordination and, in severe cases, respiratory failure, coma and death. Gastrointestinal problems including nausea, abdominal pain and diarrhea, often accompany these narcotic effects. Liver and kidney damage can appear after the acute symptoms subside. All symptoms can occur following a single oral or inhalation exposure. Milder narcotic effects followed by liver and kidney damage have been reported following dermal exposure. Although an inhalation exposure of about 1000 ppm for a few minutes to hours will cause the narcotic effects in 100% of the population, large variations in sensitivity are seen. Alcohol intake greatly increases human sensitivity to carbon tetrachloride; consequently, exposure to 250 ppm for 15 minutes can be life threatening to an alcoholic.

(RAIS, emphasis mine)

It is also characterised as a group 2B carcinogen (possibly carcinogenic to humans). There have been many epidemiological studies to confirm these effects, such as this one:

Ott et al. (1985) conducted a cohort mortality study of 1919 men employed for one or more years between 1940 and 1969 at a chemical manufacturing facility in the United States. This cohort included 226 workers assigned to a unit which produced chlorinated methanes (methyl chloride (see this volume), dichloromethane (see this volume), chloro- form (IARC, 1987b), and carbon tetrachloride) and, recently, tetrachloroethylene (IARC,1995). Exposure levels were not reported.[...] There were 42 deaths observed among the 226 workers (standardized mortality ratio (SMR), 0.6, based on national rates) [SMR, 0.8, based on company rates]. Nine cancers were observed [SMR, 0.8; 95% confidence interval (CI), 0.4–1.5, based on company rates], including three pancreatic cancers [SMR, 3.3; 95% CI, 0.7–9.7, based on company rates]. Two of the three workers who died of pancreatic cancer had been employed for less than five years.

(from IARC, emphasis mine)

Furthermore, it takes time for liver damage to be noticed. Even more so mid- 20th century, when the solvent was mostly used. Still, the toxicity of CCl4 is such, that it has been gradually replaced in dry cleaning from 1940s and 1950s and since 1960s it is no longer in use. The use of CCl4 as a pesticide was stopped in 1986.

Finally, one can experience severe health damage without actually "dropping dead" . It took time (as many things in science do) to establish and prove the connection between CCl4 and its detrimental health effects, but once this was done the old ways from the old days were abandoned.


References:

  1. Condensed Toxicity Summary for CARBON TETRACHLORIDE - RAIS, The Risk Assessment Information System
  2. Public Health Statement for Carbon Tetrachloride, Agency for Toxic Substances and Disease Registry (ATSDR), CDC
  3. International Hazard Datasheets on Occupation. Dry cleaners, ILO
  4. Malaguarnera G, Cataudella E, Giordano M, Nunnari G, Chisari G, Malaguarnera M. Toxic hepatitis in occupational exposure to solvents. World J Gastroenterol.2012; 18(22):2756–2766
  5. Control of Health and Safety Hazards in Commercial Drycleaners: Chemical Exposures, Fire Hazards, and Ergonomic Risk Factors Centers for Disease Control and Prevention (CDC)
  6. Carbon tetrachloride IARC Monographs, International Agency for Research on Cancer (IARC)
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