Chloroform is also known as trichloromethane, methane chloride, or methyltrichloride. It is a colorless liquid with a pleasant, non-irritating odor and slightly sweet taste. Most of the chloroform found in the environment comes from industry. It will only burn when it reaches very high temperatures. Chloroform was one of the first inhaled anesthetics to be used during surgery, but it is not used for anesthesia today. Nearly all the chloroform made in the United States today is used to make other chemicals, but some is sold or traded to other countries. We also import chloroform.

Chloroform enters the environment from chemical companies, paper mills, waste water from sewage treatment plants, and drinking water that contains chlorine. Chloroform can enter the air directly from factories that make or use it, and by evaporating from water and soil that contain it. It can enter water and soil when waste water that contains chlorine is released into water or soil. It may enter water and soil from spills and by leaks from storage and waste sites. In addition to its industrial production and use, small amounts of chloroform are formed as an unwanted product during the process of adding chlorine to water. Chlorine is added to most drinking water and many waste waters to destroy bacteria. There are many ways for chloroform to enter the environment, so small amounts of it are likely to be found almost everywhere.

Structural diagram: National Institutes of Health

Fate & Transport

Chloroform evaporates very quickly when exposed to air. Chloroform also dissolves easily in water, but does not stick to the soil very well. This means that it can travel down through soil to ground water where it can enter a water supply. Chloroform lasts for a long time in both the air and in the ground water. Most chloroform in the air eventually breaks down, but this process is slow. The breakdown products in air include phosgene, which is more toxi than chloroform, and hydrogen chloride, which is also toxic. Some chloroform may break down in soil. Chloroform does not appear to build up in great amounts in plants and animals, but we find some small amounts of chloroform in foods.

Exposure Pathways

You are probably exposed to small amounts of chloroform by drinking water and beverages (such as soft drinks) made using water that contains it. You can also get chloroform in your body by eating food, by breathing air, and by skin contact with water that contains it. You are most likely to be exposed to chloroform by drinking water and breathing indoor or outdoor air containing it. The amount of chloroform normally expected to be present in air ranges from 0.02 to 0.05 parts of chloroform per billion parts of air (ppb) and from 2 to 44 ppb in treated drinking water. However, in some places, chloroform concentrations may be higher than 44 ppb. It is estimated that the concentration of chloroform in surface water is 0.1 ppb, the concentration in untreated ground water is 0.1 ppb, and the amount in soil is 0.1 ppb. Even though these levels seem low, much higher levels have been recorded. As much as 610 ppb was found in air at a municipal landfill and up to 88 ppb was found in treated municipal drinking water. Drinking water derived from well water near a hazardous waste site contained 1,900 ppb, and ground water taken near a hazardous waste site also contained 1,900 ppb. Surface water containing 394 ppb has been found, and more than 0.13 ppb has been found in soil at hazardous waste sites. Chloroform has been found in the air from all areas of the United States and nearly all of the public drinking water supplies. We do not know how many areas have surface water, ground water, or soil that contains chloroform.

The average amount of chloroform that you might be exposed to on a typical day by breathing air in various places ranges from 2 to 5 micrograms per day (ug/day) in rural areas, 6 to 200 ug/day in cities, and 80 to 2,200 ug/day in areas near major sources of the chemical. The estimated amount of chloroform you probably are exposed to in drinking water ranges from 4 to 88 ug/day. We cannot estimate the amounts that you may be exposed to by eating food and coming into contact with water that has chloroform in it. Swimming in swimming pools allows chloroform to be absorbed through a person's skin. People who work at or near chemical plants and factories that make or use chloroform can be exposed to higher than normal amounts of chloroform. Higher exposures might occur in workers at drinking water treatment plants, waste water treatment plants, and paper and pulp mills. People who operate waste-burning equipment may also be exposed to higher than normal levels. The National Institute for Occupational Safety and Health (NIOSH) estimated that 95,778 individuals in the United States have had the potential for occupational exposure to chloroform.


Chloroform can enter your body if you breathe air, eat food, or drink water that contains chloroform. Chloroform easily enters your body through the skin. Therefore, chloroform may also enter your body if you take a bath or shower in water containing chloroform. In addition, you can breathe in chloroform if the shower water is hot enough for chloroform to evaporate. Studies in people and in animals show that after you breathe air or eat food that has chloroform in it, the chloroform can quickly enter your bloodstream from your lungs or intestines. Inside your body, chloroform is carried by the blood to all parts of your body, such as your liver and kidneys. Chloroform usually collects in body fat. Some of the chloroform that enters your body leaves unchanged in the air that you breathe out, and some chloroform in your body is broken down into other chemicals. These chemicals are known as breakdown products, and some of them can attach to other chemicals inside the cells of your body and may cause harmful effects if they collect in high enough amounts in your body. Some of the breakdown products also leave the body in the air you breathe out. Only a small amount of the breakdown products leaves the body in the urine and stool.

Health Effects

In humans, chloroform affects the central nervous system (brain), liver, and kidneys after a person breaths air or drinks liquids that contain large amounts of chloroform. Chloroform was used as an anesthetic during surgery for many years before its harmful effects on the liver and kidneys were recognized. Breathing about 900 parts of chloroform in a million parts of air (900 ppm or 900,000 ppb) for a short time causes fatigue, dizziness, and headache. If you breathe air, eat food, or drink water that has small amounts of chloroform, over a long period of time the chloroform may damage your liver and kidneys. Large amounts of chloroform can cause sores when the chloroform touches your skin.

We do not know whether chloroform causes harmful reproductive effects or birth defects in people. Miscarriages occurred in rats and mice that breathed smaller amounts of chloroform during pregnancy and in rats that ate chloroform during pregnancy. Abnormal sperm were found in mice that breathed small amounts of chloroform for a few days. Offspring of rats and mice that breathed chloroform during pregnancy had birth defects.

Results of studies of people who drank chlorinated water showed a possible link between the chloroform in chlorinated water and the occurrence of cancer of the colon and urinary bladder. Cancer of the liver and kidneys developed in rats and mice that ate food or drank water for a long time that had large amounts of chloroform in it. We do not know whether liver and kidney cancer would develop in people after long-term exposure to chloroform in drinking water. Based on animal studies, the Department of Health and Human Services has determined that chloroform may reasonably be anticipated to be a carcinogen (a substance that causes cancer). The International Agency for Research on Cancer has determined that chloroform is possibly carcinogenic to humans. The EPA has determined that chloroform is a probably human carcinogen.

Information excerpted from:

Toxicological Profile for Chloroform August 1995 Update

Agency for Toxic Substances and Disease Registry
U.S. Dept. of Health and Human Services