Highlights from Worldwide Scientific Studies

Government authorities around the world, academics and industry have conducted and continue to conduct extensive research on formaldehyde. The results of a small fraction of this extensive scientific research are summarized below.
> Irritation Studies
> Cancer Studies
> Asthma Studies
> Reproduction/Children's Development Studies

Irritation Studies

Formaldehyde can be irritating to the eyes, nose and throat, but for most people, irritation is temporary and reversible ("A Recommended Occupational Exposure Limit for Formaldehdye Based on Irritation," Dennis Paustenbach, et al., Journal of Toxicology and Environmental Health, 1997). It is difficult to measure levels at which irritation begins due to the subjective nature of comparison ("The Use of Noncancer Endpoints as a Basis for Establishing a Reference Concentration for Formaldehyde," Joel Bender, Reg. Toxicology and Pharmacology, February 2002). The eyes are most sensitive to formaldehyde exposure: The lowest level at which many people can begin to smell formaldehyde is about 0.3 parts per million (ppm).

In controlled chamber studies, individuals begin to sense eye irritation at about 0.5 ppm; 5 to 20 percent report eye irritation at 0.5 to 1 ppm; and greater certainty for sensory irritation occurred at 1 ppm and above (Bender). (In these controlled studies, persons not exposed to formaldehyde often reported a 20-30% response rate for eye, nose and throat irritation. Thus, the background rate of response was often higher than the rate in people reporting subjective signs of irritation at low levels of formaldehyde exposure.)

An expert panel review of over 150 published studies found that eye irritation does not become significant until around 1 ppm, and moderate to severe eye, nose, and throat irritation occurs at 2 to 3 ppm.

While some agencies have used a level as low as 0.1 ppm as a threshold for irritation, the expert panel found that a level of 0.3 ppm would protect against nearly all irritation. In fact, the expert panel found that a level of 1.0 ppm would avoid eye irritation -- the most sensitive endpoint -- in 75-95% of all people exposed (Paustenbach).

In any event, normal environmental exposures are below these levels. An U.S. Environmental Protection Agency study found a new home measured 0.076 ppm when brand new and 0.045 ppm after 30 days ("Residential Indoor Air Formaldehyde Testing Program: A Pilot Study," M. Koontz, et al, prepared for U.S. EPA, 1996).

Cancer Studies

Nasal or Other Respiratory Tract Cancer: Concern about whether formaldehyde might cause cancer in humans arose in the late 1970s and early 1980s, when it was discovered that high levels of formaldehyde (6-15 parts per million) caused nasal cancer in laboratory rats. Low levels (at or below 2 ppm) did not cause cancer in the animals, and scientists set about trying to learn why this was the case.

After more than two decades of research -- making formaldehyde one of the most thoroughly examined chemicals in history -- there is widespread scientific recognition that the effects observed in the respiratory tract, specifically the nose, in laboratory animals at levels of 6 to 15 ppm will not occur in people exposed to much lower levels (such as typical levels of hundredths of a ppm). This is because scientists now have a good understanding of how formaldehyde causes nasal cancer in animals at high levels. Unless levels get high enough to kill cells, nasal cancer is not expected to occur. Thus, at the levels to which people are exposed, most scientists believe that there is essentially no risk of any form of respiratory cancer. An international review completed in 2002 stated this in more formal scientific terms: "There is no convincing evidence of increased risks of nasopharyngeal cancer in cohort studies of populations of professionals or industrial workers exposed to formaldehyde, since the total number of cases of this rare cancer is small."

New Epidemiology Developments: The Organisation for Economic Co-operation and Development's (OECD) 2002 SIDS Initial Assessment Profile states that, "In some studies increased risks of various non-respiratory tract cancers . . . have been observed, but without any consistent pattern and without evidence of a causal relationship with formaldehyde exposure. Since kinetic studies indicate that most inhaled formaldehyde is deposited within the upper respiratory tract, available evidence for tumours at sites other than the respiratory tract does not fulfill criteria of causality (e.g. consistency, biological plausibility)."

Three papers recently published report conflicting results with respect to formaldehyde occupational exposure and an association with leukemia. An association between formaldehyde and leukemia is not thought to be probable based on the current scientific understanding of the biology of how formaldehyde acts in the body. Inhaled formaldehyde is expected to act on the upper respiratory tract and not at distant sites in the body.

It is important to remember that almost all of the exposure studied by these researchers occurred during the 1940s, 1950s, 1960s, and 1970s. The levels of formaldehyde exposure in today's workplaces have declined substantially. So while these studies may be of interest in a historical context they should be evaluated in the context of current exposure levels. The new studies add to the large body of data on formaldehyde, but do not change the conclusion that current regulatory limits are protective.
Answers to Your Questions About the New Studies

More Details on Cancer Research: Evaluating the multitude of prior studies, scientific experts and regulators have focused most of their attention on nasopharyngeal cancers specifically, or on potential respiratory tract cancer generally. A review by the CIIT Centers for Health Research noted that increases in tumors at sites other than the respiratory tract have been reported sporadically, with little consistent pattern. In 1999, the CIIT, with input from scientists associated with the U.S. Environmental Protection Agency, Health Canada and academic peer reviewers, performed a thorough evaluation of twenty years of formaldehyde research. Using modeling based on human and animal data, CIIT predicted negligible risk of respiratory cancer at environmentally relevant levels (Formaldehyde: Hazard Characterization and dose-response assessment for carcinogenicity by the route of inhalation, revised ed. 1999, CIIT Centers for Health Research).

Numerous other authoritative groups from around the globe, including the Organisation for Economic Co-operation and Development, SIDS Initial Assessment Profile April 2002, the German MAK Commission (which sets occupational exposure levels), and the U.S. Consumer Product Safety Commission have reached similar conclusions.

A recent OECD and World Health Organization review found that formaldehyde is unlikely to cause cancer at doses that are not cytotoxic (high enough to kill cells) and sustained. Thus, cancer from inhaled formaldehyde is not expected to occur at the levels to which humans are exposed.
Learn more about OECD's review.

Asthma Studies

Formaldehyde exposure has not been demonstrated to cause bronchial asthma. The Agency for Toxic Substances and Disease Registry states that investigations into this possibility have provided very limited evidence of an association. A report by the National Academy of Sciences Institute of Medicine similarly found inadequate evidence of any association between formaldehyde exposure and asthma induction. Several clinical investigations of asthma cases suspected to be due to formaldehyde failed to confirm even a single case based on inhalation tests. There are also studies indicating that asthmatic individuals are not more sensitive to the irritant effects of formaldehyde than healthy people (National Academy of Sciences Institute of Medicine - "Clearing the Air: Asthma and Indoor Air Exposures" and Joel Bender - "The Use of Noncancer Endpoints as a Basis for Establishing a Reference Concentration for Formaldehyde"). For more information visit: www.atsdr.cdc.gov.

Reproduction/Childrens' Development Studies

Formaldehyde is not considered to have reproductive or developmental effects on humans. A comprehensive review of the scientific literature concluded: "Given formaldehyde's rapid metabolism and reactivity, reproductive and developmental effects appear unlikely from low inhalation and dermal exposure." (James Collins, et al. - "A Review of Adverse Pregnancy Outcomes and Formaldehyde Exposure in Human and Animal Studies").