Toxicity of Formaldehyde
Formaldehyde is a high-production-volume chemical with a wide array of uses. Formaldehyde (gas) is listed in the Eleventh Report on Carcinogens (RoC) as reasonably anticipated to be a human carcinogen based on limited evidence of carcinogenicity in humans and sufficient evidence of carcinogenicity in laboratory animals; it was first listed in the 2nd RoC (NTP 1981). Formaldehyde (all physical forms) was nominated by NIEHS for possible reclassification in the 12th RoC based on the 2004 review by the International Agency for Research on Cancer, which concluded that there was sufficient evidence for the carcinogenicity of formaldehyde in humans.
The human exposure to Formaldehyde is enormous and Formaldehyde is produced in very large amounts (billions of pounds per year in the United States) by catalytic oxidation of methanol. Formaldehyde is produced in humans and animals as Formaldehyde is a simple, one-carbon molecule that is rapidly metabolized, is endogenously produced, and is also formed through the metabolism of many xenobiotic agents. Because of these issues, typical biological indices of exposure, such as levels of formaldehyde or its metabolites in blood or urine, have proven to be ineffective measures of exposure. Formaldehyde can bind covalently to single-stranded DNA and protein to form crosslinks, or with human serum albumin or the N-terminal valine of hemoglobin to form molecular adducts, and these reaction products of formaldehyde might serve as biomarkers for exposure to formaldehyde.
Occupational exposure to formaldehyde is highly variable and can occur in numerous industries, including the manufacture of formaldehyde and formaldehyde-based resins, wood-composite and furniture production, plastics production, histology and pathology, embalming and biology laboratories, foundries, fiberglass production, construction, agriculture, and firefighting, among others. In fact, because formaldehyde is ubiquitous, it has been suggested that occupational exposure to formaldehyde occurs in all work places. Formaldehyde is also ubiquitous in the environment and has been detected in indoor and outdoor air; in treated drinking water, bottled drinking water, surface water, and groundwater; on land and in the soil; and in numerous types of food. The primary source of exposure is from inhalation of formaldehyde gas in indoor settings (both residential and occupational); however, formaldehyde also may adsorb to respirable particles, providing a source of additional exposure. Major sources of formaldehyde exposure for the general public have included combustion sources (both indoor and outdoor sources including industrial and automobile emissions, home cooking and heating, and cigarette smoke), off-gassing from numerous construction and home furnishing products, and off-gassing from numerous consumer goods. Ingestion of food and water can also be a significant source of exposure to formaldehyde.
Numerous agencies, including the Department of Homeland Security, CPSC, DOT, EPA, FDA, HUD, the Mine Safety and Health Administration, OSHA, ACGIH, and NIOSH, have developed regulations and guidelines to reduce exposure to formaldehyde.
A large number of epidemiological studies have evaluated the relationship between formaldehyde exposure and carcinogenicity in humans and have in general confirmed that there is an increased risk of lymphohematopoietic, nasopharyngeal,sinonosal and brain cancers to humans due to formaldehyde exposure.
Some studies have confirmed the link of maternal exposure to high amounts of formaldehyde during pregnancy and increased incidences of benign and malignant tumors of the gastrointestinal tract.
Formaldehyde is a direct-acting genotoxic compound that affects multiple gene expression pathways, including those involved in DNA synthesis and repair and regulation of cell proliferation and produces mutations in a number of diverse ways.
In vitro studies with mammalian and human cells were positive for DNA adducts, DNA-protein crosslinks, DNA-DNA crosslinks, unscheduled DNA synthesis, single-strand breaks, mutations, and cytogenetic effects (chromosomal aberrations, sister chromatid exchange, and micronucleus induction). In in vivo studies in rats, formaldehyde caused DNA-protein crosslinks (in the nasal mucosa and fetal liver but not bone marrow), DNA strand breaks (lymphocytes and liver), dominant lethal mutations, chromosomal aberrations (pulmonary lavage cells and bone marrow in one of two studies), and micronucleus induction in the gastrointestinal tract.
The overwhelming consensus is that Formaldehyde is a carcinogenic mutagen in high doses.
See other articles on this blog on where formaldahyde is found in common foods
Final Report on Carcinogens. National Toxicology Program. Re. Carcinog. Backgr. Doc. 2010, Jan; (10-5981): i-512.