Formaldehyde is an important precursor to many other materials and chemical compounds. In 1996, the installed capacity for the production of formaldehyde was estimated to be 8.7 million tons per year. It is mainly used in the production of industrial resins, e.g., for particle board and coatings.

In view of its widespread use, toxicity, and volatility, formaldehyde poses a significant danger to human health. In 2011, the US National Toxicology Program described formaldehyde as “known to be a human carcinogen”

The safety of formaldehyde is very complicated. It occurs naturally and is “an essential intermediate in cellular metabolism in mammals and humans.”It is not acutely toxic as ingestion of many milliliters is tolerated. The main concerns are associated with chronic (long-term) exposure by inhalation. This may happen through three main sources: thermal or chemical decomposition of formaldehyde-based resins, emission from aqueous formaldehyde solutions (i.e. embalming fluids), and the production of formaldehyde resulting from the combustion of a variety of organic compounds (for example, exhaust gases). As formaldehyde resins are used in many construction materials it is one of the more common indoor air pollutants. At concentrations above 0.1 ppm in air formaldehyde can irritate the eyes and mucous membranes, resulting in watery eyes. Formaldehyde inhaled at this concentration may cause headaches, a burning sensation in the throat, and difficulty breathing, and can trigger or aggravate asthma symptoms

In the residential environment, formaldehyde exposure comes from a number of different routes; formaldehyde can off-gas from wood products, such as plywood or particle board, but it is produced by paints, varnishes, floor finishes, and cigarette smoking as well. In July 2016, the EPA released a pre-publication version of its final rule on Formaldehyde Emission Standards for Composite Wood Products. These new rules will impact manufacturers, importers, distributors, and retailers of products containing composite wood, including fiberboard, particleboard, and various laminated products, who will need to comply with more stringent record-keeping and labeling requirements.

Formaldehyde inhalation has also shown to cause oxidative stress and inflammation in animals. Mice studied over an exposure to a high dose of formaldehyde (3ppm), showed increased levels in plasma. This result suggests that FA inhalation either decreased NO production or increased NO scavenging, which may be an anti-stress mechanism in the body. Formaldehyde inhalation changes the sensitivity of the immune system, which influences oxidative stress.