Brian Barton
Chloroform is a clear, colourless liquid with a sweet odour. It is a chlorinated volatile organic compound (Cl-VOC) that can exist naturally in the environment, such as in mineral water and soil. It is also released into the environment through various human activities, including manufacturing processes, disinfection procedures, and chemical reactions involving chlorine and organic compounds. Chloroform has been linked to adverse health effects, including liver damage and potential carcinogenic properties. The presence of chloroform in the environment raises concerns about its impact on human health, particularly through exposure via contaminated air, water, food, and skin contact. This raises the question: Is chloroform considered a primary pollutant?
| Characteristics | Values |
|---|---|
| Chloroform Flux | 660 +/-220 Gg yr-1 |
| Natural Emissions % | 90% |
| Largest Single Source | Offshore sea water |
| Soil Processes | 220 +/-100 Gg yr-1 |
| Other Natural Sources | Volcanic and geological |
| Non-natural Sources | 66 +/-23 Gg yr-1 |
| Occupational Settings | Chloroform manufacturing plants, Fluorocarbon-22 manufacturing plants, etc. |
| Health Effects | Affects the central nervous system, liver, and kidneys |
| Short-term Exposure Effects | Tiredness, dizziness, and headache |
| Long-term Exposure Effects | Affects liver and kidney function |
| Toxic Effects | Jaundice and burning urination |
| Carcinogenic | Yes |
| Entry Points | Breathing, eating, drinking, skin penetration |
| Risk of Cancer | High in Philadelphia due to drinking water |
| Chlorination Benefits | Decreased incidence of waterborne diseases |
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What You'll Learn
Chloroform is a carcinogen
Chloroform is a chemical compound with a variety of industrial applications. It is used in manufacturing processes, as a solvent for many materials, and is formed during chlorination processes. Chlorinated water, such as that found in swimming pools, may contain chloroform. It is also present in some consumer products.
Chloroform has been identified as a potential carcinogen. The US Food and Drug Administration banned its use in drugs and cosmetics in the 1970s due to its carcinogenicity. Studies in experimental animals have provided sufficient evidence of carcinogenicity, with oral exposure causing tumours in two rodent species. Administration of chloroform caused liver cancer in mice of both sexes and kidney tumours in male mice and rats.
The US Department of Health and Human Services has determined that chloroform may reasonably be anticipated to be a carcinogen. This is supported by observations in animals exposed to chloroform through oral and inhalation pathways, which indicate that sustained or repeated cytotoxicity with secondary regenerative hyperplasia may lead to hepatic and renal neoplasia.
The weight of evidence suggests that chloroform is likely to be carcinogenic to humans by all routes of exposure under high-exposure conditions that lead to cytotoxicity and regenerative hyperplasia. However, it is not likely to be carcinogenic under exposure conditions that do not cause these cellular changes.
While chlorinated drinking water may pose a risk of chloroform exposure, the benefits of chlorination in terms of reducing waterborne diseases are considered to outweigh this risk. Nevertheless, it is important to recognise chloroform as a potential carcinogen and take steps to minimise exposure, especially in occupational settings where exposure may be more likely or occur at higher concentrations.
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Chloroform in drinking water
Chloroform is a chemical compound that can be found in a variety of occupational settings, including manufacturing plants and various industries. The general population may be exposed to chloroform through contaminated air, drinking water, and food. Chloroform can also enter the body through skin contact with chlorinated waters, such as during bathing or swimming, or through the use of consumer products containing this compound.
The presence of chloroform in drinking water is a significant concern due to its potential health risks. Short-term exposure to high concentrations of chloroform in water can cause tiredness, dizziness, and headaches. More worryingly, long-term exposure to chloroform in drinking water can lead to more severe health issues. Chloroform affects the central nervous system, liver, and kidneys, and prolonged exposure can impact their function. Toxic effects may include jaundice and painful urination.
The US Department of Health and Human Services has determined that chloroform is anticipated to be a carcinogen. This means that consuming drinking water contaminated with chloroform may increase the risk of cancer. In Philadelphia, for example, it has been reported that a significant portion of the excess environmental risk of cancer is attributed to chloroform-contaminated drinking water.
However, it is important to note that the risks associated with low-level exposures to chloroform in drinking water due to chlorination are generally outweighed by the benefits of chlorination. Chlorination significantly reduces the incidence of waterborne diseases, which pose a much more immediate and severe threat to public health. Nevertheless, ongoing monitoring and regulation of chloroform levels in drinking water are crucial to ensure that the potential health risks are minimised.
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Chloroform's impact on human health
Chloroform, also known as trichloromethane or methyltrichloride, is a colourless liquid with a slightly sweet taste and a pleasant, non-irritating odour. It is a human-made chemical compound that has been widely used in various industrial and manufacturing processes.
Chloroform has significant impacts on human health, primarily affecting the central nervous system, liver, and kidneys. Short-term exposure to high concentrations of chloroform in air, water, or food can cause tiredness, dizziness, and headaches. Longer-term exposure to high levels of chloroform can lead to more severe health issues, including potential damage to liver and kidney function. Toxic effects may include jaundice and painful urination. It is rapidly eliminated from the body, but the cumulative effects of prolonged exposure can be harmful.
One of the most concerning aspects of chloroform's impact on human health is its potential carcinogenicity. The US Department of Health and Human Services has determined, based on animal studies, that chloroform may be reasonably anticipated to cause cancer. This is particularly relevant to drinking water contaminated by chloroform, which accounts for a significant portion of the excess environmental risk of cancer in certain areas, such as Philadelphia. However, it is important to note that the risks of cancer from low-level exposure to chlorinated drinking water are generally outweighed by the benefits of chlorination in reducing waterborne diseases.
Occupational exposure to chloroform is a significant concern. Individuals working in various industries, including chloroform manufacturing, fluorocarbon-22 manufacturing, ethylene dichloride manufacturing, internal combustion engine production, pesticide manufacturing, pulp and paper mills, food processing, and paint stores, may be at risk of chloroform exposure. The use of personal protective equipment and adequate ventilation in these settings is crucial to minimising health risks.
The general population may also be exposed to chloroform through contaminated air, drinking water, food, and consumer products. Skin contact during bathing or swimming in chlorinated water is another potential source of exposure. Age, sex, diet, family traits, lifestyle, and overall health status can all influence the impact of chloroform exposure on an individual's health. By understanding the effects of chloroform, we can make informed decisions and implement measures to protect public health and minimise the harmful consequences of this pollutant.
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Chloroform's presence in the environment
Chloroform, or trichloromethane (CHCl3), has been observed in the environment for many years. It is present in the air, water, and soil. Chloroform is a pollutant that affects the central nervous system, liver, and kidneys. Its presence in the environment is a result of human activity and natural processes.
Human activities that release chloroform into the environment include its use in manufacturing processes, as a solvent, and during chlorination. Occupational settings where chloroform exposure may occur include chloroform manufacturing plants, fluorocarbon-22 manufacturing plants, ethylene dichloride manufacturing plants, internal combustion engine industries, pesticide manufacturing plants, pulp and paper mills, food processing industries, and paint stores. The use of chlorinated water, such as in swimming pools, can also lead to chloroform exposure through skin contact.
Natural processes also contribute to chloroform's presence in the environment. It is formed through the use of strong oxidizing agents on organic material in the presence of chloride ions, similar to processes occurring in soils. Offshore seawater is the largest single source of natural chloroform emissions, followed by soil processes.
The average global atmospheric concentration of chloroform has been calculated to be 18.5 pmol mol-1, with more than 90% of emissions being natural in origin. Chloroform partitions preferentially into the atmosphere, and it is widely dispersed in the aquatic environment, even being naturally present in some mineral waters.
While chloroform has been found to contaminate drinking water, current environmental concentrations do not present an ecotoxicological risk. Studies have shown that even fish in their embryonic and larval stages, when they are most susceptible, are not significantly affected. However, the US Department of Health and Human Services has determined that chloroform may be anticipated to be a carcinogen, and high levels of exposure can cause adverse health effects such as tiredness, dizziness, headaches, and liver and kidney problems.
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Chloroform's use in manufacturing
Chloroform is a colourless, dense liquid with a sweet smell. It is produced on a large scale as a precursor to refrigerants and polytetrafluoroethylene (PTFE). Chloroform is also used in the manufacturing of pesticides, as well as being a solvent for lipids, rubber, alkaloids, waxes, gutta-percha, and resins. It is also used as a cleaning agent, a grain fumigant, and in fire extinguishers.
Industrially, chloroform is produced by heating a mixture of chlorine and either methyl chloride (CH4). At 400–500 °C, free radical halogenation occurs, which converts these precursors to progressively more chlorinated compounds. The output of this process is a mixture of the four chloromethanes: chloromethane, methylene chloride (dichloromethane), trichloromethane (chloroform), and tetrachloromethane (carbon tetrachloride). These can then be separated by distillation.
Before the Montreal Protocol was enforced, most of the chloroform produced in the United States was used in the production of chlorodifluoromethane (R-22). This is done by reacting chloroform with hydrofluoric acid (HF), which fluorinates the CHCl3 molecule and releases hydrochloric acid as a byproduct. However, its production remains high, as it is a key precursor of PTFE.
Chloroform was once used as an inhalational anaesthetic between the 19th century and the first half of the 20th century. It was first demonstrated by Scottish obstetrician James Y. Simpson in 1847, who helped to popularise the drug for use in medicine. By 1895, about 750,000 doses a week were being produced in Britain. However, the application of chloroform remained dangerous, and many deaths occurred through accidental overdose.
Today, chloroform is recognised as a pollutant, affecting the central nervous system, liver, and kidneys. Short-term exposure to high concentrations of chloroform in the air causes tiredness, dizziness, and headaches. Longer-term exposure to high levels of chloroform in the air, or in food and drinking water, can affect liver and kidney function, and may include toxic effects such as jaundice and burning urination. The US Department of Health and Human Services has determined that chloroform may reasonably be anticipated to be a carcinogen.
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Frequently asked questions
Chloroform is a compound that can be found in a variety of occupational settings, such as manufacturing plants and food processing industries. It is also present in some natural sources, including offshore seawater and soil processes.
Chloroform can affect the central nervous system, liver, and kidneys. Short-term exposure to high concentrations of chloroform can cause tiredness, dizziness, and headaches. Longer-term exposure or ingestion through contaminated water or food can lead to more severe liver and kidney issues, and it is also anticipated to be a carcinogen.
While chloroform is considered a pollutant, it is not clear whether it is a primary pollutant. It is found in the environment due to both natural and human-induced processes. Natural sources, such as offshore seawater and soil, contribute to around 90% of chloroform emissions. However, human activities, including manufacturing and chlorination processes, also release chloroform into the environment.
