Composite Woods / Substrates Hazard Spectrum

Composite wood products are widely used for applications such as countertop substrates and in cabinetry, doors, and millwork. HBN ranks types of composite wood materials on a simplified spectrum below.[1] Products in the green categories are typically better options than those in the orange or red, and products in the yellow categories are generally less preferable than those at the top, but are better choices than those at the bottom.

A primary issue for composite wood products is that they commonly contain added formaldehyde (a carcinogen and asthmagen). Formaldehyde can be emitted from composite wood products over time. The best way to avoid formaldehyde exposures is to purchase products that do not contain any formaldehyde in the first place. Alternatively, choose products that have been tested to have consistently low formaldehyde emissions. Products designated as NAF (No Added Formaldehyde) and ULEF (Ultra-Low-Emitting Formaldehyde) are preferred. For a list of manufacturers making NAF or ULEF products, consult the Composite Panel Association’s Buyers Guide

Another consideration is the type of composite wood used. You can reduce toxic exposures by selecting composites with the smallest amount of binder: plywood has the least amount of binder (3.5% by weight) of composite woods, far less than MDF (10% binder by weight), or particleboard (12.4% binder by weight). 

Note that both national (TSCA Title VI) and California-based (CARB) regulations that legally limit formaldehyde emissions in composite wood only apply to hardwood plywood, MDF, and particleboard (and products that contain them). Other composite wood products including hardboard, structural plywood, OSB, glue laminated timber, wood I-joists, and finger-jointed lumber, are exempted from the regulation.[2] Formaldehyde emission testing for these exempted products is not often disclosed and ULEF or NAF claims may not be backed up by product testing, which is required for products that are covered by TSCA/CARB. For these other products, you can still prefer those with no added urea formaldehyde (NAUF).

Another important thing to keep in mind is that formaldehyde emission testing is performed at set conditions. Manufacturers may be able to meet regulatory requirements, and even ULEF requirements, using urea formaldehyde resins by including scavenger additives - such as melamine - which bind to released formaldehyde.[3] The effectiveness of these scavengers may be diminished by hot temperatures or high humidity.[4] This means that products which meet emission requirements by using formaldehyde scavengers could release formaldehyde at much higher levels when installed in a residence without an air conditioner or with the air conditioner turned off during a hot and/or humid period. 
Whenever feasible, solid wood is preferable to composite wood because it does not require binders or other additives.

Remember to specify pre-finished solid wood to keep stains and topcoat chemicals within a factory setting and off of the building site where workers and occupants are less protected.
NAF stands for No Added Formaldehyde. Composite wood materials with this designation are bound with resins that do not contain any formaldehyde beyond the trace amounts that naturally occur in wood. Most often, these are wood pieces bound by soy-based resins or isocyanate-based resins. Products labeled as NAF through CARB or TSCA have been tested to show consistently lower levels of formaldehyde emissions than those required legally.[5]

Be aware that product literature indicating that a formaldehyde-free binder is used may only be referring to  one part of a composite wood product. For example, a soy-based binder could be used on the face and backs of a board, while formaldehyde-based binders are used to bind the core pieces. Products like this may contain four times as much of a formaldehyde-based resin as a soy-based resin.[6]

In addition, manufacturers have not completely disclosed the composition of soy-based binders, which are derived from a mixture of soy flour and petrochemicals and may contain small amounts of carcinogens.[7]
 
Binders based on isocyanates are also formaldehyde-free, but can be hazardous to workers. Isocyanates are a leading cause of work-related asthma.[8]
While there is no level of formaldehyde that is known to be safe, less is better.

If you must use a product with a formaldehyde-based binder, look for those that not only meet the CARB Phase 2/TSCA Title VI limits (below), but also have the Ultra Low Emitting Formaldehyde label, which requires demonstrating that levels are consistently well below Phase 2/TSCA limits.[9] See the note above in the Read More section about conditions that can lead to higher formaldehyde emissions, particularly with a urea formaldehyde-based binder. 
The California Air Resources Board (CARB) established limits on emissions for formaldehyde from composite wood materials manufactured or sold in California. A national rule with similar requirements, TSCA Title VI, went into effect in 2018. Hardwood plywood, medium density fiberboard (MDF) and particleboard must undergo regular testing and meet the formaldehyde emission limits set for this program.[10] 

Products that meet these emission requirements may contain a variety of binders including urea formaldehyde with scavengers. See the note above in the Read More section about conditions that can lead to higher formaldehyde emissions, particularly with a urea formaldehyde-based binder.
NAUF stands for No Added Urea Formaldehyde. Composite woods with this designation are bound with resins that do not contain urea formaldehyde (UF). However, they may contain other added formaldehyde compounds, such as phenol formaldehyde (PF). PF binders generally emit formaldehyde at lower rates than UF but are not free of those emissions.[11]
While urea formaldehyde itself presents few hazards to occupants, it contains a small amount of unreacted formaldehyde that evaporates over time, which can contribute significantly to levels of formaldehyde in a home. Urea formaldehyde may also degrade throughout its use and hence will continue to emit formaldehyde long after the product's manufacture and installation.[12] Standard urea formaldehyde resins may be modified with formaldehyde scavengers in order to meet the emission requirements of CARB/TSCA, but can emit large quantities of formaldehyde under certain conditions. See the note in the Read More section. 

Endnotes
[1] Unless otherwise noted, product content and health hazard information is based on research done by Healthy Building Network for Common Product profiles, reports, and blogs. Links to the appropriate resources are provided.

[2] California Environmental Protection Agency. “Frequently Asked Questions,” February 2016. https://www.arb.ca.gov/toxics/compwood/implementation/faq.htm.

[3] “EcoBind Resin Technology.” Hexion, October 9, 2019. https://www.hexion.com/en-us/brand/ecobind.; Frihart, Charles, James Wescott, Timothy Chafee, and Kyle Gonner. “Formaldehyde Emissions from Urea-Formaldehyde- and no-added-formaldehyde-Bonded particleboard as Influenced by Temperature and Relative Humidity.” Forest Products Journal 62, no. 7/8 (2012): 551–558.

[4] Frihart, Charles, James Wescott, Timothy Chafee, and Kyle Gonner. “Formaldehyde Emissions from Urea-Formaldehyde- and no-added-formaldehyde-Bonded particleboard as Influenced by Temperature and Relative Humidity.” Forest Products Journal 62, no. 7/8 (2012): 551–558. https://www.srs.fs.usda.gov/pubs/44004.; Frihart, Charles R., James M. Wescott, Michael J. Birkeland, and Kyle M. Gonner. “Formaldehyde Emissions from ULEF- and NAF-Bonded Commercial Hardwood Plywood as Influenced by Temperature and Relative Humidity.” In Soc. Wood Sci. Technol. Proc., 1–13, 2010. https://www.researchgate.net/publication/290484593_Formaldehyde_emissions_from_ULEF-and_NAF-bonded_commercial_hardwood_plywood_as_influenced_by_temperature_and_relative_humidity.

[5] “Comparison of Key Requirements of CARB and U.S. EPA Regulations to Reduce Formaldehyde Emissions from Composite Wood Products.” California Air Resources Board, March 22, 2018. https://ww3.arb.ca.gov/toxics/compwood/comparisontable.pdf.

[6] “Europly Plus.” Columbia Forest Products, October 15, 2019. https://www.columbiaforestproducts.com/app/uploads/2014/06/CFP044_Europly_Plus_Product_SheetWEB.pdf.

[7] See for example, Columbia Forest Products. “PureBond Material Data Safety Sheet,” May 2, 2011. https://pharosproject.net/uploads/files/sources/1214/1348168687.pdf.

[8] “OSHA Fact Sheet: Do You Have Work-Related Asthma?” U.S. Occupational Safety and Health Administration, March 2014. https://www.osha.gov/Publications/OSHA3707.pdf.

[9] “Comparison of Key Requirements of CARB and U.S. EPA Regulations to Reduce Formaldehyde Emissions from Composite Wood Products.” California Air Resources Board, March 22, 2018. https://ww3.arb.ca.gov/toxics/compwood/comparisontable.pdf.

[10] The limits vary depending on the type of composite wood product. Plywood products meet the strictest formaldehyde emission limit of the standard. The limits are: 0.05 ppm for hardwood plywood, 0.09 ppm for particleboard, 0.11 ppm for MDF, and 0.13ppm for thin MDF.

[11] Global Health & Safety Initiative. “Fact Sheet: Alternative Resin Binders for Particleboard, MDF and Wheatboard,” May 2008. http://www.healthybuilding.net/uploads/files/alternative-resin-binders-for-particleboard-medium-density-fiberboard-mdf-and-wheatboard.pdf

[12] Salthammer, Tunga, Sibel Mentese, and Rainer Marutzky. “Formaldehyde in the Indoor Environment.” Chemical Reviews 110, no. 4 (April 14, 2010): 2536–72. doi:10.1021/cr800399g.

Last updated: October 28, 2019