Formaldehyde
Formaldehyde is a colorless, flammable gas with a strong odor, commonly found in a 37% aqueous solution known as formalin, which also contains methanol to prevent polymerization. It is widely utilized in the manufacturing of plastics and serves important roles in biomedical applications as a disinfectant and preservative due to its ability to link proteins and nucleic acids. Despite its useful properties, formaldehyde is recognized as a human carcinogen, with exposure linked to various cancers, particularly squamous cell carcinomas of the upper respiratory tract. High inhalation levels can lead to tissue damage and mutations, increasing the risk of malignancy. Affected groups include workers in tissue fixation, plastic manufacturing, and occupants of prefabricated homes. The carcinogenic nature of formaldehyde was established through extensive studies, culminating in its classification as a known human carcinogen in 2011. Recent evaluations by the U.S. Environmental Protection Agency have reinforced concerns about its health risks, prompting stricter regulations regarding products containing formaldehyde. Awareness of its potential dangers has led to ongoing monitoring and varied exposure limits across different regions.
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Formaldehyde
ROC STATUS:Known to be a human carcinogen since 2011
ALSO KNOWN AS: Formalin, formic aldehyde, methaldehyde, methanol, methyl aldehyde, methylene glycol, methylene oxide
RELATED CANCERS:Squamous cell carcinomas of the upper respiratory tract
DEFINITION: Formaldehyde is a flammable, colorless gas at standard temperature and pressure with a strong, irritating odor. It is highly soluble in water and is most commonly encountered as a 37 percent aqueous solution known as formalin, which usually also contains 10 to 15 percent methanol to prevent formaldehyde polymerization. Because of its simple molecular structure and reactivity, formaldehyde is widely used as a starting material in plastics manufacturing. Because it irreversibly links proteins and nucleic acids to one another, it is useful as a disinfectant and a fixative/preservative in biomedical applications.
Exposure routes: Inhalation
Where found: Manufacturing plants, prefabricated homes and buildings, hospitals, mortuaries, smog
At risk: Workers involved in tissue fixation (morticians) and in manufacturing plastics, particleboard, wood paneling, and furniture; occupants of prefabricated homes; aestheticians; pregnant women; fetuses
ETIOLOGY AND SYMPTOMS OF ASSOCIATED CANCERS: When formaldehyde reacts with adjacent primary amine groups in proteins or other biomolecules, the resulting covalent bond prevents normal mobility and functioning of the joined molecules. Repeated or sustained exposure to high concentrations (greater than 15 parts per million) of inhaled formaldehyde is sufficient to cause tissue damage, mutations, and increased cell turnover, which can result in malignant transformation. Cells in the upper respiratory tract (the nasopharynx) are especially liable to formalin-induced cancers, which take the form of squamous cell carcinomas. Formaldehyde’s carcinogenicity has been demonstrated only in rodents exposed to very high gas concentrations over long periods of time, and extrapolation to human carcinogenicity was speculative as of 1981, when it was listed in the Second Annual Report on Carcinogens as "reasonably anticipated to be a human carcinogen." Between 1981 and 2011, studies in humans were conducted, and formaldehyde was listed as a known human carcinogen for the first time in the Twelfth Report on Carcinogens (2011).
History: Formaldehyde was first described and chemically synthesized in the 1800s, although it exists in small quantities in the atmosphere naturally and is a product of amino acid metabolism in the body. Its widespread adoption in the chemical industry prompted several large studies to search for diseases associated with exposure. According to the Report on Carcinogens, Fifteenth Edition (2021), consistent findings in epidemiological studies have shown a causal relationship between formaldehyde exposure and human cancer, including myeloid leukemia, nasopharyngeal cancer, and sinonasal cancer. Because of its many other adverse health effects, formaldehyde is subject to occupational and residential monitoring, with variable exposure limits in different jurisdictions.
In 2022 an updated analysis published by the United States Environmental Protection Agency (EPA) confirmed the carcinogenic properties of formaldehyde and highlighted that its risk to human health may be higher than previously thought. In particular, the EPA identified an increased risk of rare head and neck tumors, leukemia, and other life-threatening conditions. This report paved the way for the establishment of new regulations surrounding the manufacture, distribution, and labeling of products containing formaldehyde, such as pesticides, composite wood products, and other hazardous sources.
Bibliography
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