Formaldehyde is also a strong skin irritant and sensitiser. It causes cancer in rodents and is a suspected human carcinogen. This means there is adequate animal evidence, but no good human evidence.
Unfortunately, it is now one of those ubiquitous chemicals that is almost impossible to get away from completely. Fortunately, though, there are a lot of things you can do to reduce your exposure to it.
Most of the formaldehyde produced is used to make urea and phenol-formaldehyde resins that are primarily used in the wood industry. A further 10% of formaldehyde is used to make plastics, plasticisers, and bakelite. Small amounts of formaldehyde are used as preservatives in cosmetics and deodorants, toiletries, disinfectants, toothpaste and food contact substances. It is also used in photographic chemicals, rubber production, carpets, upholstery, dyes, textiles, fertilisers and embalming fluid (yep it is used on humans as well to preserve them after death). If you're old enough, you may remember the smell of formalin, the liquid form of formaldehyde, in the old days of cutting up rats in school laboratories.
The main sources of formaldehyde in homes and office buildings are medium-density fibreboard, hardwood plywood panelling and particleboard, literally in that order. Pressed wood products are by far the biggest source and a growing problem as a result of the large amount of this type of wood that is used in homes. It is not just used in flooring and walls, but also most new furniture is full of it. This is exacerbated by the fact that modern homes are often also very airtight, so the formaldehyde recycles in the air and ultimately through our lungs.
Factors that will determine how much formaldehyde is released from these pressed wood products include the temperature and humidity, how much pressed wood product is used in the home and the age of the wood. Higher temperatures and humidity tend to increase the release of formaldehyde, and older wood releases significantly less formaldehyde. Hence the biggest problems with formaldehyde occur in new homes or recently renovated homes and buildings. The highest levels our research team found to be in the smallest rooms in the home, such as the baby's room, because of the pressed wood products and low ventilation in these rooms. We also found extremely high levels in demountable buildings and caravans, simply because they are so airtight and have lots of formaldehyde-containing woods. The levels in demountables and caravans exceeded the occupational health and safety limit at the time.
New furniture often becomes a significant contributor to formaldehyde in the air as a result of the material being made from pressed wood.
Reducing our exposure
The main solution to the formaldehyde indoor air quality problem is twofold. The first step is to reduce the quantity of formaldehyde-bearing materials coming into our homes. This means either fewer pressed wood products or, before you bring them in the home, air them outside, perhaps in a garage or somewhere else under cover. It might only take a week or two to offgas 50% or more of the formaldehyde. The second step is to make sure you have good ventilation - so open doors and windows.
Unfortunately, many people believe plants are a good way of cleaning the air of formaldehyde. My research showed we needed more than two plants per square metre to achieve a small reduction in formaldehyde levels. This is the same reduction we achieved by opening a window one centimetre. My research has been supported by a number of other studies around the world. Plants look great inside and probably make us feel good, but they don't clean the air.
Textiles appear to be a fairly minor but important source because they often come in direct contact with the skin. Formaldehyde-based resins are used in fabrics to promote desirable qualities such as shrink resistance, permanent press, fire retardance and colourfastness. Unfortunately, many of the textile products, such as shirts, trousers and underwear, coming from overseas will have a formaldehyde residual that may cause skin irritation.
There has been a lot of media comment on these products and in about 90% of instances a good wash in warm water and being left out in the sunlight will get rid of the formaldehyde. However, in some cases we are found it almost impossible to remove the chemical and the associated irritation of the skin.
Carpets are often a source of many indoor air quality problems, but generally not formaldehyde, unless they are laid with a glue containing formaldehyde. If you can avoid the glues, you reduce your problems with carpets and indoor air quality dramatically.
Many consumer products also contain formaldehyde or formaldehyde resins. The chemical is a potentially dangerous component of some domestic cleaners, such as carpet and furniture cleaners. Varnish-like surface coatings are probably a lesser known source of contamination, but a significant level of free formaldehyde is released upon application.
UF resin is often added to waxed paper, facial tissues, napkins, sanitary products and paper towels to increase wet strength. This is why you might end up with a red nose if you use tissues too much.
Certain categories of cosmetic and toiletry products that contain high concentrations of surfactants, such as shampoos, have traditionally required formaldehyde to preserve them against contamination by gram-negative microorganisms. The usual formaldehyde concentration in these products is approximately 1%. It is also found in anti-dandruff shampoos, bubble baths and some deodorants.
Another cosmetic use of formaldehyde is as a nail hardener. Fingernails treated with formaldehyde solutions become harder and more resistant to breakage. For this application, the formaldehyde concentration is up to 5%. Several studies have found that formaldehyde emissions from some cosmetics often greatly exceed the threshold for eliciting allergic reactions with frequent or continuous use.
The best solution here is to avoid any cosmetics or personal care products that contain formaldehyde or formaldehyde releasing ingredients such as quartenium, 2-bromo - 2-nitropropane - 1,3 diol (Bronopol or BNPD), DMDM hydantion and Diazolidinyl urea.
As a general guide to reduce your exposure to this ever-present chemical, develop greater awareness and exercise your judgement in how you use products containing it.
Dr Peter Dingle PhD is an environmental and nutritional toxicologist and Associate Professor in Health and the Environment at Murdoch University, Western Australia.