Formaldehyde is a colorless, strong-smelling gas used in many industrial applications, from manufacturing building materials to producing common household goods. It is also a natural compound, produced in small amounts by most living organisms as part of their metabolic processes. Based on extensive study, major health organizations have evaluated its cancer-causing potential. The International Agency for Research on Cancer (IARC) and the U.S. National Toxicology Program (NTP) classify formaldehyde as a known human carcinogen, while the U.S. Environmental Protection Agency (EPA) has classified it as a probable human carcinogen when inhaled.
Sources of Formaldehyde Exposure
Formaldehyde is present at low levels in both indoor and outdoor air, but indoor environments typically have the highest concentrations. This is because many products common in homes and buildings release formaldehyde gas over time, a process known as off-gassing. The rate of this release is often highest when products are new.
A primary source of formaldehyde in the home comes from building materials and furnishings, particularly those made with pressed-wood products. These materials, such as particleboard, medium-density fiberboard (MDF), and plywood, are bound together with urea-formaldehyde resins. These resins can release formaldehyde gas for an extended period. Such products are frequently used in cabinets, furniture, sub-flooring, and wall sheathing. Certain insulation materials, like older urea-formaldehyde foam insulation (UFFI), were also a source, though its use has been discontinued.
Beyond construction materials, formaldehyde is present in numerous household and consumer products. It is a component in some glues, adhesives, paints, and lacquers. The textile industry uses formaldehyde-based resins to create permanent press fabrics that resist wrinkles. This chemical can also be found in some paper product coatings and as a preservative in certain personal care products and cosmetics.
Combustion is another significant source of formaldehyde exposure. Tobacco smoke contains formaldehyde, exposing both smokers and those nearby to the chemical. Other indoor combustion sources include unvented or malfunctioning gas stoves and open fireplaces. Outdoor air contains formaldehyde from sources like automobile exhaust and industrial emissions, which can then enter homes.
Health Effects of Formaldehyde
The impact of formaldehyde on human health varies depending on the concentration and duration of exposure. When formaldehyde is present in the air at levels above 0.1 parts per million (ppm), many people begin to experience acute sensory irritation. These immediate effects often include watery eyes, a burning sensation in the eyes, nose, and throat, as well as coughing and wheezing. Skin irritation, such as dermatitis, can also occur upon direct contact with solutions containing formaldehyde.
These irritant effects are the body’s initial response to the chemical’s presence. The severity of these symptoms increases with higher concentrations in the air. While these short-term effects are reversible once a person moves to fresh air, they signal the presence of formaldehyde at potentially harmful levels.
Long-term, or chronic, health effects are associated with prolonged exposure. Research has established a link between formaldehyde exposure and certain types of cancer. The strongest evidence points to an increased risk of nasopharyngeal cancer, a cancer of the upper throat behind the nose, and myeloid leukemia, a cancer of the blood-forming cells. Studies of industrial workers and professionals like embalmers, who have high occupational exposure, have consistently shown these increased risks.
The mechanism by which formaldehyde causes cancer involves its ability to damage genetic material. When inhaled, most formaldehyde is absorbed in the upper respiratory tract. The chemical can cause DNA mutations and interfere with cellular repair processes, which can lead to uncontrolled cell growth. Laboratory studies support these findings, showing formaldehyde can induce changes in the chromosomes of white blood cells.
Exposure Levels and Risk Factors
The risk of developing health problems from formaldehyde is directly tied to the concentration of the chemical in the air and the length of time a person is exposed. The danger is not uniform across the population, differing significantly between those with occupational exposure and the general public.
Professionals in certain industries face the highest and most prolonged exposures. This group includes industrial workers involved in manufacturing formaldehyde-based resins or pressed-wood products, laboratory technicians, and healthcare professionals. Morticians and embalmers are also at a high risk due to their frequent use of formalin, a water-based solution of formaldehyde. Regulatory bodies like the Occupational Safety and Health Administration (OSHA) set permissible exposure limits for workplaces, currently at 0.75 ppm over an eight-hour workday, to protect these workers.
For the general population, exposure occurs at much lower levels, primarily from indoor air in homes, schools, and offices. While formaldehyde is present in outdoor air at concentrations below 0.03 ppm, indoor levels can be significantly higher due to off-gassing from the sources previously mentioned. Sensitive subgroups, including children, the elderly, and individuals with pre-existing respiratory conditions like asthma, may experience health effects at lower concentrations.
Strategies for Limiting Exposure
Reducing formaldehyde levels within the home is achievable through several practical strategies. The most effective approach involves a combination of controlling the sources and improving indoor air quality.
- Increase ventilation. Opening windows and using fans to circulate air helps to dilute indoor concentrations of formaldehyde and move it outside. This is particularly important when new furniture or building materials are brought into the home, as off-gassing is highest when products are new.
- Make informed consumer choices. When purchasing composite wood products for furniture or cabinetry, look for items certified to meet low-emission standards. In the United States, this means products compliant with the California Air Resources Board (CARB) Phase 2 emissions standards. These products are made with resins that release significantly less formaldehyde.
- Wash new textiles. New clothing, especially those labeled as permanent press or wrinkle-resistant, should be washed before being worn. This process helps to remove residual formaldehyde resins from the fabric.
- Maintain fuel-burning appliances. Ensure that all fuel-burning appliances, such as gas stoves and furnaces, are in good working order and properly vented to the outdoors. This will prevent the buildup of combustion-related pollutants, including formaldehyde.
- Control the indoor climate. High temperatures and elevated humidity levels can increase the rate at which formaldehyde off-gasses from materials. Maintaining a moderate indoor temperature and using dehumidifiers to keep humidity levels in check can help minimize the amount of formaldehyde being released into your indoor air.