Research Note 97-9: Topic = Indoor emissions, formaldehyde, toluene






 California Environmental Protection Agency


Air Resources Board


 No. 97-9



August 1997




Brief Reports to the Scientific and Technical Community




 Research Division, John R. Holmes, Ph.D., Chief


P.O. Box 2815, Sacramento CA 98512



 Indoor Emissions of Formaldehyde
and Toluene Diisocyanate

 Formaldehyde and toluene diisocyanate are toxic chemicals that, even at low levels, can cause adverse health effects and are used in the manufacture of products that are commonly found in residences. This was the first independent study in over a decade in which formaldehyde emission rates from a large variety of known or suspected indoor product sources were measured. The results show that the major sources of formaldehyde inside residences generally emit less formaldehyde than in the past, although significant amounts of formaldehyde are still emitted from a variety of products, including pressed wood products, permanent press fabrics, and a wood floor finish. The results also indicate that toluene diisocyanate is generally not emitted from products used inside residences. The Air Resources Board will use the information gained from this study to improve guidance to the public on steps they can take to reduce their exposure to formaldehyde. The results will also be used to improve the Board's estimates of Californians' exposures to formaldehyde and toluene diisocyanate. This research was performed by Battelle.











Significance and Application:




Related Projects:




The Air Resources Board's (ARB's) Indoor Air Quality and Personal Exposure Assessment Program gathers information needed to estimate indoor exposures to air pollutants and provides guidance to the public on steps they can take to reduce their exposures. Short-term exposures to sufficient levels of two indoor pollutants, formaldehyde and toluene diisocyanate, can irritate sensitive tissues. Long-term exposures may increase the risk of cancer. These compounds have been identified as toxic air contaminants under ARB's air toxics program. In 1991, the ARB used available information to develop a public information guideline, Formaldehyde in the Home, which presents information on common sources of formaldehyde in the home and steps people can take to reduce their exposures to formaldehyde.

This project was designed to provide up-to-date emission rate measurements from a cross section of common residential products known or suspected to be indoor sources of formaldehyde or toluene diisocyanate.

Indoor levels of formaldehyde in California homes are typically several times higher than outdoor levels. Formaldehyde is used in the manufacture of widely-used, diverse products such as particle board and permanent press fabrics. Prior to this study, most of the comparative emission rate data were collected in the late 1970s/early 1980s and do not reflect current product characteristics. Also, emissions from some potentially significant sources of formaldehyde exposure, such as certain coatings and cosmetics, had not been measured earlier.

Toluene diisocyanate is used in the manufacture of polyurethane products, such as foam furniture cushions, foam carpet pads, and various polyurethane coatings. Prior to this study, only very limited information was available on toluene diisocyanate emissions from residential sources.



The investigators obtained product samples of known or suspected indoor sources of formaldehyde or toluene diisocyanate primarily from retail and wholesale outlets located in several California population centers. The investigators generally selected products with the greatest likelihood of high emissions and/or high usage in residences.

Formaldehyde emissions were measured from 55 different products, over half of which were pressed wood products. Samples of decorative laminates, permanent press fabrics, fiberglass insulation, interior latex paint, wood floor finish, wallpaper, fingernail polish/hardeners, and wet-strength paper products also were included. Toluene diisocyanate emissions were tested from 39 different polyurethane products, including foam carpet padding, foam furniture cushions, varnishes, water sealers, caulking compounds, and adhesives.

Product emission rates were measured under controlled conditions using specialized chambers. Emission rates were generally determined approximately 20 hours after each product was placed in the chamber. Emissions were alsomonitored for the duration of each chamber test using a continuous monitor. Products were tested under two different temperatures and air exchange rates chosen to represent conditions that might result in "typical" and "high level" emissions.

Four other carbonyls were analyzed along with formaldehyde. These were the toxic air contaminants acetaldehyde, propionaldehyde, methyl ethyl ketone, and methyl iso-butyl ketone. Because little was known about toluene diisocyanate emissions, products expected to emit this gas were first screened in a small chamber in batches of similar products.



The highest formaldehyde emission rates were measured from a wood floor finish, which emitted approximately 11,000 µg181g/m²/hr at the end of the test period. Initial emission rates from that product were two orders of magnitude higher. Fingernail hardeners also had rather high initial formaldehyde emissions. Of the "dry" products tested, bare pressed wood products made with urea-formaldehyde resin generally had the highest emission rates, with most of the products emitting at rates of approximately 100 to 300 µg181g/m²/hr. Wood products made with phenol-formaldehyde resin, such as softwood plywood, generally had lower emissions than products made with urea-formaldehyde resin. Laminates and other surface coat-ings acted as barriers to greatly reduce formaldehyde emissions from pressed wood products. An exception was a formaldehyde-containing finish that added its own emissions to those of the cabinet door to which it was applied.

Emission rates of new permanent press fabrics fell between those of the bare and coated pressed wood products. Normal laundering reduced emissions from permanent press shirts by about 60 percent. The product category with the lowest emissions was paper products, from which only small to negligible emissions were detected. Formaldehyde emissions from selected products during typical use conditions are listed in Table 1.




Table 1


Formaldehyde Emissions from Selected Indoor Sources

 Typical Conditions (µg/m²/hr)


Wet products


 wood floor finish



 fingernail hardener



 latex paint










Wood products


 cabinet door with acid-cured finish



 medium-density fiberboard cabinet door



 particle board



 particle board with vinyl laminate



 softwood plywood


















 new permanent-press shirts



 washed permanent-press shirts



 fiberglass insulation












Formaldehyde emission rates from wood products made with urea-formaldehyde resin, including particle board, medium density fiberboard, and hardwood plywood, generally appear to be lower than those reported in earlier studies. Emissions from wood products made with phenol-formaldehyde resin were similar to the low levels reported in the past. Formaldehyde emissions from permanent press fabrics appear to have decreased somewhat, while emissions from fiberglass products appear to be similar to earlier findings.

None of the residential products tested positive in the screening tests for toluene diisocyanate, suggesting that indoor residential exposure to this pollutant is not a major concern. One non-residential product, a concrete sealer, had high initial toluene diisocyanate emissions, with a rapid decline to low emissions within an hour after application.



This study updates our knowledge of the magnitude of formaldehyde emissions from residential sources and also provides formaldehyde emissions data for some products not previously tested. The results show that major residential sources of formaldehyde generally emit less formaldehyde than those sources did in the past. They also indicate that some simple measures, such as putting laminates on particle board or washing new permanent press fabrics, are effective in reducing formaldehyde emissions. This information will aid ARB in providing guidance to the public on steps they can take to reduce their exposure to formaldehyde. In addition, this was the first study to explore potential toluene diisocyanate emissions from a variety of residential sources; the results allow us to reasonably conclude that indoor residential exposure to this pollutant is not a major concern. Finally, the results of this study will be used to improve ARB's estimates of Californians' exposure to formaldehyde and toluene diisocyanate.