Formaldehyde is a colorless chemical compound recognized as a volatile organic compound (VOC) that readily becomes a gas at room temperature, possessing a distinctly pungent odor. It is a chemical building block widely used in manufacturing and industry, primarily as a component in resins and as a preservative. Formaldehyde’s ubiquity lies in its presence across a vast range of common, everyday environments and products. This compound is a constant feature of our indoor air, consumer goods, external environment, and even our own biology.
Sources Within Home Construction and Furnishings
The home environment is a significant source of formaldehyde exposure, mainly through off-gassing, where the chemical is slowly released into the air from materials. The largest contributors are pressed wood products used in construction and furniture, such as particleboard, medium-density fiberboard (MDF), and hardwood plywood. These materials rely on urea-formaldehyde (UF) resin for bonding, which slowly releases the compound over time.
MDF often has the highest emission rates because it contains a greater resin-to-wood ratio compared to other UF-based products. Phenol-formaldehyde (PF) resins, used in exterior-grade plywood, release formaldehyde at much lower rates than the UF resins favored for indoor products. Emissions increase noticeably under conditions of high heat and humidity, which can elevate indoor air concentrations, especially in newly built or renovated spaces. Formaldehyde is also used to give “permanent press” qualities to fabrics, including clothing and draperies, and is a component in some foam insulation and adhesives.
Presence in Everyday Consumer Goods
Exposure also comes from items consumers interact with directly, where formaldehyde or formaldehyde-releasing chemicals are incorporated for preservation. In personal care products like shampoos, lotions, cosmetics, and nail polishes, formaldehyde releasers are used as preservatives. These releasers, such as quaternium-15 or DMDM hydantoin, slowly break down in water-based products to release small amounts of formaldehyde.
This slow release is intentional, protecting the products from contamination by bacteria, mold, and fungus, thereby extending their shelf life. Formaldehyde or its releasers are also found in household cleaning agents and dishwashing liquids. The compound is utilized in certain dyes and finishes to make textiles wrinkle-resistant or to improve colorfastness, meaning it can be present as a residue on clothing.
Environmental and Combustion Emissions
Formaldehyde is generated as a byproduct of combustion, creating a constant source of emission into external and indoor air environments. This process results from the incomplete burning of carbon-containing materials, which is particularly relevant to the transportation sector. Vehicle exhaust, especially from diesel engines, is a major contributor to ambient air formaldehyde levels.
The burning of other fuels, such as in power plants, industrial processes, and natural events like wildfires, also releases formaldehyde into the atmosphere. Within the home, combustion sources include un-vented appliances like gas stoves and kerosene heaters, which release the chemical directly into the indoor air. Tobacco smoke, both primary and secondhand, represents another direct source of exposure due to the incomplete combustion of the tobacco leaves.
Natural Occurrence in Food and Human Biology
Formaldehyde is a naturally occurring compound present in small amounts in a wide variety of foods. It is a metabolic intermediate, produced as a normal part of chemical processes in living organisms, including plants, animals, and humans. Common foods like fruits (apples and pears), vegetables (green onions), and various meats and fish all naturally contain trace amounts of formaldehyde.
The natural concentration in a pear can be around 38.7 milligrams per kilogram, and in beef, it is around 8.5 parts per million. The human body constantly produces formaldehyde, generating approximately 1.5 ounces daily as a byproduct of normal cellular metabolism. This naturally generated formaldehyde is rapidly broken down by enzymes into harmless substances like carbon dioxide.