The short answer
Formaldehyde is a strong-smelling gas used in building products and resins. High or long exposure is linked to a rare nasal cancer and to myeloid leukemia. Pressed-wood products and poor ventilation raise indoor levels. Ventilation and low-emission products help.
Formaldehyde is classified as a known human carcinogen (IARC Group 1).
People are mainly exposed by breathing the gas released indoors by pressed-wood products, or at certain jobs.
It is most strongly linked to nasopharyngeal cancer and myeloid leukemia.
A carcinogen classification describes hazard — whether something can cause cancer — not your personal risk at a given exposure.
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The full explanation.
The simple version
Formaldehyde is a colorless gas with a sharp smell. It is used to make many household products and building materials. Breathing in higher amounts over time is linked to certain cancers, especially in people with heavy workplace exposure.
What formaldehyde is
Formaldehyde is a widely used industrial chemical found in pressed-wood products (like plywood and particleboard), glues and resins, some paints, permanent-press fabrics, and household cleaners. It is also used as a preservative in labs and mortuaries, and forms during combustion.
How people are exposed
Common ways people come into contact with it:
- Breathing gas released from new pressed-wood furniture, cabinets, and flooring
- Working as an embalmer, lab worker, or in manufacturing that uses formaldehyde
- Tobacco smoke and some fuel-burning appliances
- Higher indoor levels in new, poorly ventilated, or humid spaces
The cancer connection
Formaldehyde is linked to cancers of the nasopharynx (the upper part of the throat behind the nose), the nasal cavity and sinuses, and to myeloid leukemia. These links are clearest in workers with high, sustained exposure.
The International Agency for Research on Cancer (IARC), the cancer arm of the World Health Organization, places formaldehyde in Group 1, carcinogenic to humans — the strongest evidence category, meaning there is enough evidence that it can cause cancer in people. In the United States, the National Toxicology Program's Report on Carcinogens lists it as known to be a human carcinogen.
Hazard is not the same as risk
It helps to separate two ideas that are easy to mix up: hazard and risk. When an agency lists formaldehyde as a carcinogen, it is making a statement about hazard — whether the substance is capable of causing cancer under some conditions. It is not, by itself, a statement about your personal risk, which depends on how much you are exposed to, for how long, and other factors. Two substances in the same group can carry very different real-world risks. The label answers "can it cause cancer?" — not "how likely is it to cause cancer for me?"
How to lower your exposure
- Ventilate well, especially with new furniture, cabinets, or flooring
- Choose exterior-grade or low-emission pressed-wood products (labeled CARB or ULEF)
- Keep indoor humidity and temperature moderate, which lowers off-gassing
- Do not smoke indoors
If you are looking at your overall cancer risk, small, steady steps add up. See our overview of cancer prevention and what raises cancer risk to put any single exposure in context.
The bottom line
Formaldehyde is a known human carcinogen (IARC Group 1). The most important thing you can do is understand where exposure comes from and take reasonable steps to reduce it, without losing sleep over a single label. Focus your energy on the biggest, most controllable risks in your own life.
Words to know
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Common questions
▸Does formaldehyde cause cancer?
Yes. Formaldehyde is classified as a known human carcinogen, which means there is strong evidence it can cause cancer in people. How much any one person's risk rises depends on how much they are exposed to and for how long.
▸How are people exposed to formaldehyde?
Most exposure happens by breathing the gas released indoors by pressed-wood products, or at certain jobs.
▸Which cancers are linked to formaldehyde?
It is most strongly linked to nasopharyngeal cancer and myeloid leukemia.
▸How can I reduce my exposure to formaldehyde?
The main steps are ventilating your home and choosing low-emission wood products.
▸Does a carcinogen label mean I will get cancer?
No. A classification is about hazard — whether formaldehyde can cause cancer under some conditions — not a prediction that any one exposed person will develop cancer. Your actual risk depends on the amount and length of exposure and other factors.
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