2-Hexanone, also known as methyl n-butyl ketone or MBK, is a clear, colorless liquid with a somewhat sharp odor. The liquid form can easily evaporate into the air as a vapor. It is a waste product of wood pulping, coal gasification, and oil shale operations. 2-Hexanone was formerly used in paint and paint thinner and in various chemical substances. However, since it was found to have harmful health effects, it is no longer made in the United States, and its uses have been restricted. There are no known major natural sources of 2-hexanone in the environment. When 2-hexanone is released to rivers or lakes, it dissolves very easily, and it may evaporate into the air in a few days. We do not know if 2-hexanone binds to soil. When 2-hexanone is released to the water, air, or soil, it is probably broken down into smaller products, possibly within a few days.
Exposure to 2-hexanon
You can be exposed to 2-hexanone if you live near an industry or hazardous waste site that releases the liquid into wastewater or the gas form into the surrounding air. These industries include coal gasification plants, oil shale operations, and wood pulping mills. We have no information on background levels of 2-hexanone in the environment.
2-Hexanone has been found as a natural substance in foods such as cheese, nectarines, nuts, bread, and chicken muscle. We do not know the levels of 2-hexanone in these foods. 2-Hexanone has been found in milk and cream at levels up to 0.018 ppm (0.018 parts of 2-hexanone in one million parts of liquid). These levels are far below the levels that have caused harmful effects in animals. It has also been found in drinking water and soil near hazardous waste sites. Exposures at these sites may take place if you drink the contaminated water or bathe in it, if you get contaminated soil on your skin, or if you breathe the contaminated air.
Pathways for 2-hexanone in the body
2-Hexanone can enter your body when you breathe its vapors, eat food or drink water that contains it, or when you come in contact with it through your skin. When 2-hexanone is breathed in, about 75% of it is taken up and remains in the body unchanged or as a breakdown product for an unknown length of time. If it enters the body by mouth, about 65% of the chemical leaves the body slowly (in about a week), either unchanged or as breakdown products, in the breath and urine. The rest may either stay in the body or may leave the body slowly through the breath or urine. One of the breakdown products, called 2,5-hexanedione, may be responsible for the harmful effects on the nervous system. When 2-hexanone gets in through the skin, some leaves the body through the lungs and urine within a few hours. We have no information on how much stays in the body or for how long. If you live or work near a hazardous waste site, you may be exposed to 2-hexanone in the air that you breathe or in the water you drink or bathe in, if it contains small amounts of this chemical.
Health effects of 2-hexanone
The most important health concern for humans from exposure to 2-hexanone is its harmful effects on the nervous system. These effects were seen in workers who were exposed to 2-hexanone for almost a year. The major effects were weakness, numbness, and tingling in the skin of the hands and feet. Similar effects were seen in animals that ate or breathed high levels of 2-hexanone; these effects included weakness, clumsiness, and paralysis.
You should know that one way to learn whether a chemical will harm people is to determine how the body absorbs, uses, and releases the chemical. For some chemicals, animal testing may be necessary. Animal testing may also help identify such health effects as cancer or birth defects. Without laboratory animals, scientists would lose a basic method for getting information needed to make wise decisions that protect public health. Scientists have the responsibility to treat research animals with care and compassion. Scientists must comply with strict animal care guidelines because laws today protect the welfare of research animals.
Additionally, there are vigorous national and international efforts to develop alternatives to animal testing. The efforts focus on both in vitro and in silico approaches and methods. For example, the National Toxicology Program (NTP) at the National Institute of Environmental Health Sciences (NIEHS) created the NTP Interagency Center for the Evaluation of Alternative Toxicological Methods (NICEATM) in 1998. The role of NICEATM is to serve the needs of high quality, credible science by facilitating development and validation—and regulatory and public acceptance—of innovative, revised test methods that reduce, refine, and replace the use of animals in testing while strengthening protection of human health, animal health and welfare, and the environment. In Europe, similar efforts at developing alternatives to animal based testing are taking place under the aegis of the European Centre for the Validation of Alternative Methods (ECVAM).
We do not know whether 2-hexanone can cause cancer or birth defects. In one study, when pregnant rats were exposed to 2-hexanone in the air, fewer offspring lived after birth, and those that did survive had low birth weights.
Many of the studies in which the health effects of 2-hexanone in humans or animals were reported did not use pure 2-hexanone. Therefore, we do not know whether the results were caused by 2-hexanone itself or by the other chemicals in the mixture.
Medical tests for exposure to 2-hexanone
Tests can be used to find out whether you have recently been exposed to 2-hexanone. The tests measure levels of 2-hexanone or its breakdown products in blood or urine. These tests require special equipment and are done in a special laboratory, so they are usually not available in a doctor's office. However, these tests cannot be used to predict whether harmful effects will occur.
- The Agency for Toxic Substances and Disease Registry
- Interagency Coordinating Committee on the Validation of Alternative Methods
- European Centre for the Validation of Alternative Methods
- Institute for Laboratory Animal Research
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