Formaldehyde & Indoor Air Quality

What is formaldehyde?

When you hear the word “formaldehyde,” thoughts of eighth grade science class come to mind. Remember shelves lined with glass jars containing dead animals stored in formaldehyde in order to keep their body parts from deteriorating? In addition to acting as a preservative, formaldehyde has many other uses and may even be found in your home.

At room temperature, formaldehyde is a colorless, flammable gas with a strong and pungent odor. It is a member of a large group of compounds known as volatile organic compounds (VOCs) which will off-gas into the air. Inhaling high concentrations of off- gassed formaldehyde could lead to health problems [1]. Formaldehyde is responsible for the “new” smell of products and buildings and is both a good preservative, as well as an excellent adhesive. Formaldehyde is known to contribute to poor indoor air quality and is suspected of being a contributing factor with “sick building” syndrome [2].

 

Sources of Formaldehyde

Formaldehyde is widely used in the building and home furnishings industries. Pressed wood products use adhesive containing urea formaldehyde that can break down, releasing formaldehyde into the air. Medium density fiberboard is a major contributor of formaldehyde in the home environment due to a high ratio of urea formaldehyde containing adhesive to wood. The presence of large quantities of pressed wood products used in mobile homes, manufactured homes, new homes, and recently remodeled homes contributes to higher levels of formaldehyde. Older homes typically have lower formaldehyde levels because emission of formaldehyde from pressed wood products decreases over time [3]. Formaldehyde is also found in foam insulation, permanent press fabrics, cosmetics, and as a preservative in paint and coatings. Combustion of natural gas, wood, gasoline, and tobacco can lead to its release into the air. Present at lower levels in outdoor air, sources of atmospheric formaldehyde include car exhaust, emission from certain industrial sources, and formation due to chemical reactions amongst combustion pollutants.

 

Health effects of formaldehyde exposure

Inhaling formaldehyde can cause both short-term irritation and long-term health effects, such as cancer [4]. The potential health effects depend on the amount of formaldehyde inhaled, the length of exposure time, and an individual’s sensitivity. For example, people with asthma, children, and the elderly are typically more sensitive to the effects of formaldehyde in the air. Low levels of formaldehyde exposure can cause irritation of the eyes, nose, throat, and skin. At higher concentrations, formaldehyde exposure can also cause irritation of the lungs’ passageways. At very high exposure levels, symptoms can include chest tightness, coughing, wheezing, headaches, nausea, and fatigue. The U.S. Environmental Protection Agency had previously classified formaldehyde as a “probable” human carcinogen, based on studies of lab animals repeatedly exposed to high levels of formaldehyde [5].

 

What affects the concentration of formaldehyde in indoor air?

The concentration of formaldehyde is typically several times higher indoors than outdoors. Indoor formaldehyde air concentration levels depend on what material releases the formaldehyde, the air exchange rate, the temperature, and the humidity. Increasing the flow of air between the outside and the inside decreases the formaldehyde level.

Conversely, decreasing the inflow of outdoor air by sealing a building increases the formaldehyde level indoors. Formaldehyde levels in a residence can change with the season and time of day. Both increased temperature and increased humidity can result in increased formaldehyde emission into the air. Therefore, formaldehyde levels may be high on a hot and humid day and low on a cool, dry day. Understanding these factors is important when considering measurement of formaldehyde levels. For information regarding guidelines for improving indoor air, visit The U.S. Green Building Council website http://www.usgbc.org/. The U. S. Green Building Council works toward its mission of market transformation through its internationally recognized LEED green building certification program. It provides building owners and operators a concise framework for identifying and implementing practical and measurable green building design, construction, operations and maintenance solutions.

 

Compendium Method TO-11A:

Determination of Formaldehyde in Ambient Air Using Adsorbent Cartridge Followed by High Performance Liquid Chromatography (HPLC) [6]

TO-11A is a method for the determination of formaldehyde and other carbonyl compounds (aldehydes and ketones) in ambient air utilizing a coated-solid adsorbent followed by high performance liquid chromatography with UV detection. Several methods have been developed over the years for the determination of formaldehyde. Earlier methods utilized wet chemical technology involving a bubbler or impinger containing a reactive reagent. However, impinger air sampling is no longer the preferred method of formaldehyde determination due to numerous weaknesses such as:

  • Labor intensivity
  • Use of acidic/hazardous reagents
  • Lack of sensitivity
  • Prone to interferences
  • Poor reproducibility at ambient concentration levels

As the EPA's interest focused upon formaldehyde and its sources, the development of passive personal sampling devices (PSDs) developed [7]. However, because of the design and flow rate limitation, passive PSDs require long exposure time (up to 7 days) in the atmosphere to meet traditional bubbler technique sensitivities. Consequently, the passive PSD had limited application to ambient monitoring. The development of method TO-11A allows greater volumes of air to be sampled, thus enabling better sensitivity and lower detection limits. This technique is based on reacting airborne carbonyls with 2,4- dinitrophenylhydrazine (2,4-DNPH) coated on an adsorbent cartridge followed by separation and analysis of the hydrazone derivative by high performance liquid chromatography.

The sampling method provides a time-weighted average (TWA) sample. It can be used for long-term (1-24 hr) sampling of ambient air where the concentration of formaldehyde is generally in the low ppb (v/v) range or for short-term (5-60 min) sampling where the concentration of formaldehyde could reach the ppm (v/v) levels.

The method recommends the use of pre-coated DNPH cartridges that are now commercially available from several major suppliers. These low pressure drop cartridges allow for a sampling flow of up to 2.0 liters/minute.

 

Conclusion

You may not be able to avoid coming in contact with formaldehyde-containing products in your normal daily routine. You can reduce your formaldehyde exposure by purchasing pressed wood products that meet ANSI A208.1, purchasing furniture that has edges and surfaces laminated or coated, washing new permanent press fabrics before use, bringing large amounts of fresh air into your home, buying used or antique furniture, restricting tobacco smoking to outdoors, and keeping indoor temperature and humidity at moderate levels.

 

References:

Minnesota Department of Health Fact Sheet, Formaldehyde Facts, April 2010

Heimlich, Joe E., ‘Sick Building Syndrome’, The Invisible Environment Fact Sheet Series, 2008

Godish, Thad, Ph.D., ‘Indoor Air Quality Notes: Formaldehyde-Our Homes and Health’, No.1, 2nd Ed., Summer, 1989

California Department of Health Services, http://www.cdph.ca.gov/programs/hesis/Documents/formaldehyde.pdf

U.S. EPA, http://www.epa.gov/iris/subst/0419.htm

[6,7] http://www.epa.gov/ttnamti1/files/ambient/airtox/to-11ar.pdf

 

Authored by Brian Mills, Microbac Laboratories, Inc.