Volume 26, Number 5
Jul 2003

Interior Paints and Indoor Air Pollution

Reprinted with permission from Air Quality Sciences' newsletter airfAQS, Volume 11, Issue 1

Interior wall paints are recognized as a significant source of VOCs in the indoor environment. The main indoor air quality concern from paints is the release of total volatile organic chemicals (TVOCs), many of which are irritants or odorants, and can present other toxic exposure concerns. Actual chemicals released by paints depend on their chemical formulation.

When new paint is drying, indoor VOC levels can be 1000 times higher than outdoor levels. Paint releases VOCs into the air. Because of the large surface areas typically covered by paint in a room, VOC emissions can be significant. A room that is 12x12 feet will have a painted wall and ceiling surface are close to 432 ft² which is three times the exposed area of a flooring or ceiling product. Since paints are often applied in occupied spaces, and VOC emissions can continue even 6 months after application, people are more likely to be exposed to vapors from freshly painted surfaces.

Many paint manufacturers market their products as "No-VOC" or "VOC-free." The initial perception is that a product marketed in this manner does not contain any VOCs and, therefore, will not contribute VOCs into the indoor environment. However, these claims usually refer to content, and recent studies have shown that products can still release VOCs into the air.

The United States Environmental Protection Agency (USEPA) has conducted recent studies of paints and coatings measuring emissions from products marked as "No-VOC." These tests have shown that VOC content does not necessarily correlate with VOC emissions from the product. USEPA Test Method 24, which determines a product's VOC content, is based on a gravimetric weight loss of the product upon heating. This method is generally not sensitive or reproducible for content levels less than 0.1 to 1%. Consequently, it is common to find VOC emissions from a product even though it has been reported to have a "No-VOC" content based on Method 24.

USEPA's studies on coatings and paint show that some VOCs such as formaldehyde may be generated as byproducts or by chemical reactions during coating application; these VOCs cannot be measured in the content analysis. A recent study shows that certain conversion varnishes actually form formaldehyde during the curing process after being applied to a substrate. Thus, the emission levels are greater than those expected from the content analysis. (See the Journal of the Air Waste and Management Association, Vol. 49, 1999.)

The USEPA, AQS, and others study paints using environmental chamber techniques. Standard procedures are available for applying paint to common wallboard and studying their chemical emission levels over time. Studies are performed in small chambers according to ASTM D 5116-97. These studies identify the chemicals being emitted and their levels, and predict how long they will be emitted. The data can be compared to existing standards and guidelines to determine the paint's acceptability for indoor exposures.

AQS conducted a study of various interior paints including flat latex, semi gloss, and gloss paints by Method 24 and also applied them to wallboard and studied their emission releases over time in an environmental chamber. The objective was to compare manufacturers' claims, results obtained by Method 24, and results obtained by emission testing.

As can be seen from the chart, there are variations not only among the different types of paint, but also within manufacturers of a single type. Even paints that were labeled as having no VOCs had TVOC emissions above zero when tested in an emissions chamber. The data show that there is a difference between content measurements and airborne emissions. However, paints which did have zero TVOCs listed by content did have the lowest emission measurements when compared with the other paints.

AQS uses environmental chamber testing and the State of Washington guidelines to test low emitting paints as a testing partner for the GREENGUARD Certification Program™.

For more information on Product Emissions testing, contact AQS at 770-933-0638, Ext. 265 or email at info@aqs.com.