Formaldehyde in Indoor Air

Formaldehyde is a colourless gas that is commonly found in the indoor air of homes. It can be emitted from building materials and furnishings, in particular those made from pressed-wood products with formaldehyde-based adhesives. It is also a by-product of combustion and can enter indoor air from sources such as smoking, vehicle exhaust, wood-burning fireplaces and stoves, and improperly vented gas or oil burning appliances.

What are the health effects of formaldehyde?

Formaldehyde is an irritant, and exposure to high concentrations of formaldehyde can cause burning sensations in the eyes, nose and throat. Long-term exposure to moderate formaldehyde concentrations (at levels lower than those causing irritation) have also been linked to breathing problems, especially in children with asthma.

Although formaldehyde is a known carcinogen, the risk of developing cancer from formaldehyde exposure at concentrations found in most Canadian homes is essentially zero.

Formaldehyde can be found in the air of most, if not all, homes. It is, however, generally below the levels recommended by Health Canada. Formaldehyde may be a concern for people with respiratory problems (such as children with asthma) following new home construction or renovations, when levels are generally at their highest.

How do I reduce formaldehyde levels in my home?

Formaldehyde emissions from building materials and furnishings will generally decrease over time. Increased ventilation during and after construction or renovations can help reduce indoor formaldehyde levels. Other ways to lower formaldehyde include:

  • Don't allow anyone to smoke inside the home.
  • Make sure fireplaces and woodstoves are in good working condition to prevent smoke from getting into your living environment. Keep your chimney clean and clear of obstructions.
  • Don't idle cars or other gas powered equipment in attached garages or near doors or windows.
  • For some building and household products, there may be no or low formaldehyde options available, ask retailers or manufacturers for details.
  • Allow pressed-wood products to "air out" before bringing them into your home.

What are Health Canada's recommended levels for formaldehyde?

Health Canada's Residential Indoor Air Quality Guideline for formaldehyde recommends maximum exposure limits of;

  • Short-term exposure: 123 µg/m³ (100 ppb) based on a 1-hour average to protect against irritation of the eyes, nose or throat.
  • Long-term exposure: 50 µg/m³ (or 40 ppb) based on a minimum 8-hour average, to protect against respiratory symptoms in children with asthma.

Health Canada's recommended short-term exposure limit is 1/10th of the lowest level at which symptoms have been observed, in order to protect more sensitive individuals. In direct exposure studies, formaldehyde has been shown to cause irritation of the eyes, nose and throat at 1230 µg/m³ (1000 ppb). However, people may vary in their sensitivity to formaldehyde and some may experience symptoms at lower levels.

Health Canada's recommended long-term exposure limit is set to protect children with asthma, who may be more sensitive to the effects of formaldehyde. Long-term exposure to formaldehyde in indoor air has been associated with increased allergic sensitivity, airway inflammation and physician-diagnosed asthma.

Health Canada's recommended levels also protect against the potential cancer risk from formaldehyde. Formaldehyde is classified as "carcinogenic to humans" by the International Agency for Research on Cancer (IARC). Industrial workers exposed to high levels of formaldehyde as part of their jobs have shown a higher risk of developing rare forms of cancer that affect the upper respiratory systems. The risk of developing cancer from formaldehyde levels found in Canadian homes, however, is essentially zero.

What are the main sources of formaldehyde?

Most formaldehyde in homes comes from building materials used in the home, especially pressed-wood products, such as particleboard, medium density fiberboard, and hardwood plywood panelling. Pressed-wood products that use adhesives containing urea-formaldehyde resins generally release more formaldehyde than those containing phenol-formaldehyde resins. Other sources of formaldehyde include furnishings, some paints and adhesives, varnishes and floor finishes and permanent press fabrics.

In general, these products will emit less and less formaldehyde over time. However, it can take weeks, months or even years to stop completely. Formaldehyde levels are, therefore, generally higher in newly built or newly renovated homes. More formaldehyde is also released on hot and humid days, so levels are often higher in the summer.

Formaldehyde may also be produced as by-product of combustion. Smoking is a significant source of indoor formaldehyde. It can also be released from wood stoves, and fireplaces, if they are not properly vented to the outside. Vehicle exhaust entering from attached garages or outside may also contain formaldehyde.

Should I test my home for formaldehyde?

Testing your home for formaldehyde is generally not necessary. If you are concerned that the formaldehyde levels may be high, because of health symptoms, odours or obvious formaldehyde sources, the best step is to remove sources if possible and to increase ventilation. If you are having health symptoms, talk to a doctor, as only they can determine if the symptoms are related to your environment.

Formaldehyde testing may be available from some environmental consultants and/or industrial hygienists, although they primarily sell these services to business and may not be affordable for the average homeowner.

If for some reason sampling is deemed necessary, it is recommend to sample for 8-24 hours and to take the average formaldehyde level. The sampling method used should follow a recognized protocol such as those published by the US Environmental Protection Agency (EPA) or United States Department of Labour's Occupational Safety and Health Administration (OSHA). Samples should be sent to an accredited laboratory for analysis. Common accreditations include the American Industrial Hygiene Association (AIHA) or Canadian Association for Laboratory Accreditation (CALA).

What about Urea formaldehyde-based thermal insulation (UFFI)?

UFFI, which is foamed in place and used to insulate buildings, has been banned in Canada under the Hazardous Products Act (HPA) since December 1980. UFFI was banned due to the high levels of formaldehyde that were given off during the installation process, as well as the continued off-gassing of formaldehyde from poorly installed insulation. The amount of formaldehyde released by UFFI was highest when first installed and decreased over time. As a result, UFFI installed before 1980 would have little effect on indoor formaldehyde levels today. If UFFI gets wet, however, it could begin to break down and may release more formaldehyde. Wet or deteriorating UFFI should be removed by a specialist and the source of the moisture problem should be repaired. Some provinces require homeowners to declare if they have UFFI installed, and this issue is generally raised during the re-sale of older homes.

For more information on UFFI please see Health Canada's It's Your Health factsheet on Formaldehyde or the Canada Mortgage and Housing Corporation (CMHC)'s  About your House fact sheet on UFFI.

What are the Residential Indoor Air Quality Guidelines?

The Residential Indoor Air Quality Guidelines are Health Canada's official position on the health risks posed by a specific indoor contaminant, based on a review of the best scientific information available. They summarize the known health effects, detail the indoor sources, and provide a recommended exposure level below which health effects are unlikely to occur. The Guidelines are recommendations only and are not an enforceable standard under any regulation. They are meant to serve as a scientific basis for activities to reduce the risk from indoor contaminants. This could include the development of regulations or standards or the production of communication materials aimed at the general public.

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