Three types of closely related cresols exist: ortho-cresol (o-cresol), meta-cresol (m-cresol), and para-cresol (p-cresol). Pure cresols are colorless chemicals, but they may be found in brown mixtures such as creosote and cresylic acids (e.g., wood preservatives). Because these three types of cresols are manufactured separately and as mixtures, they can be found both separately and together. Cresols can be either solid or liquid, depending on how pure they are; pure cresols are solid, while mixtures tend to be liquid. Cresols have a medicinal smell (odor) and when dissolved in water, they give it a medicinal smell and taste. Cresols do not evaporate quickly from water, but in rivers and lakes, they can be removed quickly by bacteria. Dissolved cresols can pass through soil into underground water sources. This may be a problem at hazardous waste sites where cresols are buried. Once cresols are in the water table, they may stay there for months without changing. Cresols in air quickly change and break down into smaller chemicals, some of which irritate the eyes. Cresols can also irritate the eyes.
Cresols are natural products that are present in many foods and in animal and human urine. They are also present in wood and tobacco smoke, crude oil, and coal tar. In addition, cresols also are man-made and used as disinfectants and deodorizers, to dissolve substances, and as starting chemicals for making other chemicals.
Exposure to cresols
People are most likely to be exposed to cresols by breathing, eating, or drinking them. You can breathe cresols from the air. We do not have enough information to know the background levels of cresols in air, water, or soil, but we do know where they are released. Cresols in the air can come from car exhaust. People are likely to be exposed to cresols in cities and crowded neighborhoods where traffic is heavy. Houses that are heated with coal or wood also may send cresols into the air through chimneys. People who live near factories that burn trash and garbage may breathe cresols from the smokestacks. Smokestacks of factories, electrical power plants, and oil refineries may send cresols into the air, and people who live close to these places may breathe in cresols. People who work in places that use or make cresols may breathe cresols in the air or get cresols on their skin. Cigarette smoke contains cresols, so people who smoke cigarettes are likely to breathe in more cresols than people who do not smoke. Nonsmokers may also breathe in cresols from the cigarette smoke of nearby smokers.
You may eat cresols in your food. Some foods that contain cresols are tomatoes, tomato ketchup, asparagus, cheeses, butter, bacon, and smoked foods. Drinks can also contain cresols. Coffee, black tea, wine, Scotch whiskey, whiskey, brandy, and rum can contain small amounts of cresols. People who live near garbage dumps or places where chemicals are stored or were buried, including hazardous waste sites, may have large amounts of cresols in their well water. They may drink some cresols in the tap water. At work places where cresols are produced or used, people may be exposed to large amounts of cresols.
Pathways for cresols in the body
Cresols can enter your body tissues quickly if you breathe air containing cresol gas or mist (droplets of cresol-containing liquid in the air), drink water or eat food that contains cresols, or allow your skin to come into contact with substances that contain cresols. If you live near a hazardous waste site, you might come into contact with cresols by drinking water, touching substances, or breathing in air that contains cresols. Cresols may also be formed in your body from other compounds, such as toluene and the amino acid tyrosine, which is present in most proteins. Most of the cresols that enter your body are quickly changed to other substances and leave your body in the urine within 1 day.
Health effects of cresols
If you were to eat food or drink water contaminated with very high levels of cresols, you might feel a burning in the mouth and throat as well as stomach pains. If your skin were in contact with a substance containing high cresol levels, you might develop a rash or severe irritation. In some cases, a severe chemical burn might result. If you came into contact with high enough levels of cresols, for example, by drinking or spilling on your skin a substance containing large amounts of cresols, you might become anemic, experience kidney problems, become unconscious, or even die.
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).
Studies in animals have not found any additional effects that would occur after long-term exposure to lower levels of cresols. It is possible that some of the effects in humans listed above, such as kidney problems and anemia, might occur at lower levels if exposure occurs over a longer time period. Effects on the nervous system, such as loss of coordination and twitching of muscles, are produced by low levels of cresols in animals, but we do not know whether low levels also cause such effects in humans. Cresols may enhance the ability of carcinogenic chemicals to produce tumors in animals, and they have some ability to interact with mammalian genetic material in the test tube, but they have not been shown to produce cancer in humans or animals. The EPA has determined that cresols are possible human carcinogens. Animal studies suggest that cresols probably would not produce birth defects or affect reproduction in humans.
Medical tests for exposure to cresols
Samples of your urine can be tested for the presence of cresols, although this test is not routinely available in hospitals and clinics. This test will not tell you whether or not you will have any adverse health effects. The urine sample would have to be taken within 1 day of your exposure to be valid. Because cresols occur naturally in people, and at levels that vary from one individual to the next, results from tests for cresol exposure should be compared to values obtained from the same individual either before exposure or several days after exposure. Small changes might be caused by variation in daily diet. You should also be aware that an increased presence of cresols in the urine could indicate exposure to toluene, a related compound, rather than cresols. However, toluene exposure would also result in elevated urinary levels of hippuric acid; cresol exposure would not.
Disclaimer: This article is taken wholly from, or contains information that was originally published by, the Agency for Toxic Substances and Disease Registry. Topic editors and authors for the Encyclopedia of Earth may have edited its content or added new information. The use of information from the Agency for Toxic Substances and Disease Registry should not be construed as support for or endorsement by that organization for any new information added by EoE personnel, or for any editing of the original content.