Kanpur is a major leather-processing centre in Uttar Pradesh in North India, with an estimated 20,000 tannery workers.

Kanpur is a major leather-processing centre in Uttar Pradesh in North India, with an estimated 20,000 tannery workers. Leather production includes many operations with different exposures that can be harmful to the health of the workers, and particularly be carcinogenic. Some compounds in the tanning process are considered as probably being carcinogenic to humans.
(ZUMA Press, Inc. / Alamy Stock Photo)

Formalin, an aqueous solution of formaldehyde (40% formaldehyde by volume or 37% formaldehyde by weight) combined with a stabilizer, is used to preserve biological specimens and tissue samples, as an embalming fluid, and in dilute form as a disinfectant or antibacterial wash.


Formaldehyde under ordinary conditions is a colorless flammable gas with a pungent and irritating odor. It dissolves easily in water but readily escapes from the water in its gaseous form. It occurs in the environment as an intermediate byproduct of the combustion of methane gas, of forest fires, of automobile exhaust, and of tobacco smoke. When formaldehyde is produced in the upper atmosphere as the result of the action of sunlight and oxygen on atmospheric methane, it becomes part of smog. In 1969, interstellar formaldehyde was first detected by a team of radio astronomers at the National Radio Astronomy Observatory. In 2014, astronomers at the Llano de Chajnantor Observatory in the Atacama Desert in Chile detected the presence of formaldehyde in the comae (envelopes surrounding the comets' nuclei) of two comets.

In living organisms, formaldehyde is produced in minute amounts during the metabolism of amino acids and can be detected in human blood. Formaldehyde does not, however, remain in the environment for long periods of time; it is readily broken down by sunlight or by bacteria in the soil or water. It does not accumulate in aquatic organisms or in the mammalian food chain. In humans, formaldehyde is quickly metabolized and converted into formic acid. The greatest danger that formaldehyde poses to human health is chronic (long-term) inhalation of its vapor.

Pure formaldehyde is a colorless gas at room temperature. It freezes at -134°F (-92°C) and boils at -6°F (-21°C) but can become explosive at temperatures above 122°F (50°C). Formalin boils at a temperature of 205°F (96°C). Most people can begin to detect the smell of formaldehyde at a concentration of 0.05 parts per million (ppm); eye irritation begins at levels of 0.5 ppm and higher. Occupational exposure is limited to 0.3 ppm, according to standards set by the National Institute for Occupational Safety and Health (NIOSH). The U.S. Environmental Protection Agency (EPA) has set an upper limit of 0.016 ppm formaldehyde in the air in any of the agency's new buildings.


Formaldehyde was first discovered in 1859 by Alexander Butlerov (1828–1886), a Russian chemist. It was first produced by August Wilhelm von Hofmann (1818–1892), a German chemist, by passing methanol vapor over a heated platinum wire. A metal catalyst is still used in the commercial production of formaldehyde by the formox process.

Formaldehyde was first produced commercially in Germany in the 1880s and then in France, Belgium, and the United States by the early 1900s. Early production was in small lots, usually between 10 and 45 pounds and was used primarily to make formalin for embalming and preserving medical specimens.

The use of formaldehyde in the manufacture of plastics began in 1907, when Belgian chemist Leo Baekeland (1863–1944) used a resin made with formaldehyde to produce Bakelite, the first hard moldable plastic. In the 1940s, German manufacturers produced the first commercial-grade particleboard using formaldehyde, which led to its widespread use in the furniture and construction industries and a vastly increased demand for formaldehyde. Almost all formaldehyde produced as of 2018 was used in industrial applications.


Formaldehyde is present in low levels in the human body itself as well as in the natural environment, which means that all people worldwide have modest levels of exposure to it. In the developed countries, formaldehyde is rarely encountered in its pure form except in factories in which it is produced as a precursor to manufacturing synthetic resins and other chemical compounds. As of 2002, at least 8.7 million tons of formaldehyde were manufactured worldwide each year, and the amount has increased since then, although exact figures for the rate of production were not available as of 2018.

Most people do not suffer serious health effects from exposure to formaldehyde vapor in the home or office environment, although infants, the elderly, and people with asthma or other respiratory disorders may feel uncomfortable. Workers in industries that produce or use formaldehyde, particularly those in the particleboard and synthetic coatings industries, are at greatest risk of serious health effects. As of 2018, about 4 million people worked in the 12,000 plants located across Canada and the United States that either produced or used formaldehyde.


More than 99% of the formaldehyde produced industrially is used to make different types of resins and other industrial chemicals; it is a useful compound for this purpose because it is a stable molecule that binds tightly with other substances and thus links them together. Phenolic, urea, and melamine resins are used as adhesives and binders in the manufacture of paper and pulp, furniture, and synthetic fibers; in textile finishing; and in making plastics and coatings. Polyacetal resins are also used in the manufacture of plastics. In addition to its role in the manufacture of resins, formaldehyde is used as an intermediate step in the production of such chemicals as 1,4 butanediol (used as a solvent and to make certain types of plastics) and methylene diphenyl diisocyanate (used to make polyurethane paints and foams).

Slightly less than 1% of manufactured formaldehyde is used for embalming or for medical and forensic purposes. It can be used as a tissue fixative and preservative; as an antibacterial and antifungal agent to treat aquarium fish infected by parasites; to prevent contamination of vaccines by viruses and bacteria during the production process; as a topical application for removing skin warts; and as a source of compounds used to prevent the growth of bacteria in cosmetics, creams, and other personal care products. Last, formaldehyde is added to animal feeds to keep the feed free of Salmonella bacteria, which can cause severe digestive disorders in farm animals.

Interstellar formaldehyde has attracted growing interest on the part of astronomers and astrochemists because of its usefulness as a probe for studying dust particles in interstellar clouds.

Causes and symptoms


Formaldehyde can enter the human or natural environment in several ways:


Exposure to formaldehyde can produce the following symptoms:

Any of a group of organic compounds in which a carbon atom shares a double bond with an oxygen atom; a single bond with a hydrogen atom; and a single bond with another atom or group of atoms. Formaldehyde is the simplest of the aldehydes.
Any substance, form of radiation, or radioactive material that promotes the development of cancer.
An abnormal accumulation of fluid in the space between the skin and body organs or in body cavities. Inhaling high levels of formaldehyde vapor can cause edema of the lungs.
Food chain—
An arrangement of the organisms in an ecological community with food producers at the bottom and predators above them, in the order in which each organism uses the next lower member as a food source.
Related to or dealing with the application of scientific or medical information to legal problems, usually criminal cases.
An aqueous solution of formaldehyde used to preserve biological specimens, as an embalming fluid, and in dilute form as a disinfectant and bactericide.
Formox process—
A trademarked method for manufacturing formaldehyde by oxidizing methanol (wood alcohol) on the surface of a silver-based catalyst or iron oxide mixed with either molybdenum or vanadium.
A chemical compound consisting of four atoms of hydrogen and one atom of carbon. It is the main component of natural gas.
A simple alcohol commonly known as wood alcohol because it used to be derived from the distillation of wood.
A molecule of low molecular weight capable of reacting with other molecules of low molecular weight to form very large molecules called polymers. Formaldehyde in its simplest form is a monomer.
Pertaining to the nose and the upper part of the throat. Inhalation of formaldehyde is associated with nasopharyngeal cancer.
Any of a class of very large natural or synthetic molecules formed from multiples of monomers.
A solid or sticky (viscous) substance of either plant-derived or synthetic origin that can be converted into polymers. Many plants secrete resins in response to injury to protect themselves from insect invasion.
Referring to any medication applied to the outside of the body (skin, hair, nails, or eyes). Topical formaldehyde preparations are used to remove warts.
The tendency of a liquid to evaporate rapidly; to pass off readily in the form of vapor.

In regard to the risk of cancer, formaldehyde has been considered a suspected or known carcinogen since the early 2000s. The International Agency on Research for Cancer (IARC) classified formaldehyde as a cause of nasopharyngeal cancer in 2004 and a cause of myeloid leukemia in 2012, based on data from animal studies and European workers exposed to formaldehyde. In June 2011, the twelfth edition of the National Toxicology Program (NTP) report on carcinogens changed the status of formaldehyde from “reasonably anticipated to be a human carcinogen” to “known to be a human carcinogen”.

In 2018, however, a U.S. study that summarizes investigations carried out since 2011 reported that “new findings are consistently negative, and integration of all available evidence challenges the earlier conclusions that formaldehyde causes leukemia.” A Korean study, also published in 2018, stated that “additional evidence is needed to confirm the relationship between formaldehyde exposure and nasopharyngeal cancer.” One reason for the ongoing debate about formaldehyde as a carcinogen is that many industrial workers exposed to it are exposed to a mixture of other chemicals as well. In addition, the mechanisms by which formaldehyde is thought to cause cancer were not completely understood as of 2018.

There is some evidence from European researchers that occupational exposure to formaldehyde may be associated with an increased risk of amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease. A group of Danish physicians reported in 2017 that formaldehyde exposure is associated with a 1.3-fold increase in the rate of ALS among male workers. Further studies were under way as of 2018.



The National Institute of Occupational Safety and Health (NIOSH) recommends the following measures to prevent health problems from exposure to formaldehyde:


NIOSH recommends the following treatments for exposure to formaldehyde:


Most people exposed to formaldehyde vapor in homes or offices do not suffer lasting ill effects, although people with asthma or chronic obstructive pulmonary disease may experience increased wheezing or difficulty breathing. There were at least six known cases of human suicides resulting from ingesting formalin as of 2018, with lethal doses ranging between four and five ounces.


Additional precautions for safety in regard to formaldehyde include the following:

See also Agency for Toxic Substances and Disease Registry ; Sick building syndrome ; Smog .



Board on Environmental Studies and Toxicology, Division on Earth and Life Studies, National Research Council. Review of the Formaldehyde Assessment in the National Toxicology Program 12th Report on Carcinogens. Washington, DC: National Academies Press, 2014.

IARC Working Group on the Evaluation of Carcinogenic Risks to Humans. Some Chemicals Present in Industrial and Consumer Products, Food and Drinking-water. Lyon: IARC, 2013.

Lippmann, Morton, and Richard B. Schlesinger. Environmental Health Science: Recognition, Evaluation, and Control of Chemical Health Hazards, 2nd ed. New York: Oxford University Press, 2018.

Patton, Amy, editor. Formaldehyde: Synthesis, Applications, and Potential Health Effects. New York: Nova, 2015.


Amiri, A., and A. Turner-Henson. “The Roles of Formaldehyde Exposure and Oxidative Stress in Fetal Growth in the Second Trimester.” Journal of Obstetric, Gynecologic, and Neonatal Nursing 46 (January-February 2017): 51–62.

Dahlgren, J. G., and P. J. Talbott. “Asthma from Hair Straightening Treatment Containing Formaldehyde: Two Cases and a Review of the Literature.” Toxicology and Industrial Health 34 (April 2018): 262–69.

Fagan, P., et al. “Sugar and Aldehyde Content in Flavored Electronic Cigarette Liquids.” Nicotine and Tobacco Research. Published electronically November 22, 2017. doi: 10.1093/ntr/ntx234.

Kwon, S. C., et al. “Does Formaldehyde Have a Causal Association with Nasopharyngeal Cancer and Leukaemia?” Annals of Occupational and Environmental Medicine 30 (January 31, 2018): 5.

Mendel, J. R., et al. “Brand Switching and Toxic Chemicals in Cigarette Smoke: A National Study.” PLoS One 13 (January 11, 2018): e0189928.

Mundt, K. A., et al. “Six Years after the NRC Review of EPA's Draft IRIS Toxicological Review of Formaldehyde: Regulatory Implications of New Science in Evaluating Formaldehyde Leukemogenicity.” Regulatory Toxicology and Pharmacology 92 (February 2018): 472–90.

Seals, R. M., et al. “Occupational Formaldehyde and Amyotrophic Lateral Sclerosis.” European Journal of Epidemiology 32 (October 2017): 893–99.


American Chemistry Council. “Formaldehyde.” (accessed April 16, 2018).

International Agency for Research on Cancer (IARC). “Formaldehyde.” IARC Monographs on the Evaluation of Carcinogenic Risks to Humans. (accessed April 15, 2018).

National Institute for Occupational Safety and Health (NIOSH). “International Chemical Safety Cards (ICSC): Formaldehyde.” (accessed April 15, 2018).

National Library of Medicine PubChem Open Chemistry Database. “Formaldehyde.” (accessed April 15, 2018).

National Library of Medicine TOXNET. “HSDB: Formaldehyde.” (accessed April 15, 2018).


Agency for Toxic Substances and Disease Registry (ATSDR), 4770 Buford Hwy. NE, Atlanta, GA, 30341, (800) 232-4636, , .

American Chemistry Council, 700 Second St. NE, Washington, DC, (202) 249-7000, Fax: (202) 249-6100, .

Centers for Disease Control and Prevention (CDC), 1600 Clifton Rd., Atlanta, GA, 30329, (800) CDC-INFO, .

International Agency for Research on Cancer (IARC), 150 Cours Albert Thomas, Lyon, France, 69372 Lyon CEDEX 08, +33 04 72 73 84 85, .

International Programme on Chemical Safety (IPCS), Avenue Appia 20, Geneva, Switzerland, 1202 Geneva, +41 22 791211, .

National Institute of Environmental Health Sciences (NIEHS), 111 T. W. Alexander Dr., Durham, NC, 27709, (919) 541-3345, Fax: (301) 480-2978,, .

U.S. Environmental Protection Agency (EPA), 1200 Pennsylvania Ave. NW, Washington, DC, 20460, (202) 564-4700, .

Rebecca J. Frey, PhD

  This information is not a tool for self-diagnosis or a substitute for professional care.