Composite Woods / Substrates Hazard Spectrum

Below is a listing of composite woods (commonly used as substrates), which HBN has ranked on a simplified spectrum. Products appearing green are better options than those that appear red, and products that appear yellow contain more toxic substances than those at the top, but are better choices than those at the bottom. The primary issue to be aware of is that composite wood products can contain formaldehyde (a carcinogen and asthmagen) or other potentially hazardous volatile organic compounds (VOCs).

The best way to avoid formaldehyde exposures is to purchase products that do not contain any formaldehyde. For a list of manufacturers making products that meet the guidelines below, consult the Composite Panel Association’s 2016 Buyers Guide which includes a list of manufacturers making products designated as NAF, meaning No Added Formaldehyde. The list also includes less preferred No Added Urea Formaldehyde (NAUF) products.

You can also 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).

A variety of indoor air quality certification (IAQ) programs evaluate emissions of formaldehyde and other VOCs from building products. They measure emissions for 14 days after the product has been unpackaged to estimate long term emissions. Generally, these standards are based upon conditions in an office building or school where a ventilation system is always diluting the emissions. IAQ certifications may not be protective in a home or apartment building where forced ventilation is minimal or nonexistent. Only programs that use a “residential scenario” to assess emissions will be protective. Even this highest standard might fail under harsh conditions, such as the high heat and humidity scenario described below (see Standard Formaldehyde Resins). Again, the best safeguard is to avoid formaldehyde altogether by specifying solid wood or NAF composite woods.

Whenever feasible, solid woods are preferable to composite woods because they do not require binders or other additives.

Remember to specify pre-finished solid woods 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 woods 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 methylene diisocyanate (MDI) .

But beware: the NAF term sometimes applies to just one part of a composite wood product and can lead to some confusion. For example, a soy-based binder could be used on the face and backs of a board, but formaldehyde-based binders are used to bind the core pieces.  These products may contain four times more phenol formaldehyde than soy-based resin.

In addition, manufacturers have only incompletely 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.

Binders based on MDI are also formaldehyde-free, but can be hazardous to workers. Exposures to isocyanates at very low levels, even a drop on the skin, may cause the onset of asthma disease.  

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, be sure that it meets not only the CARB Phase 2 limits (below), but also has the Ultra Low Emitting Formaldehyde label, which requires demonstrating that levels are consistently well below Phase 2 limits. See note below, however, about possible breakdowns, particularly with a urea formaldehyde based binder.

The California Air Resources (CARB) has established limits on emissions for formaldehyde from composite wood.  However, hardboard, structural plywood, structural composite lumber, OSB, glue-lams and wood I-joists, finger-jointed lumber, wood packaging are all exempted from the regulation.

A national version of the CARB Phase 2 standard has been approved by the Environmental Protection Agency.  These products, labeled “TSCA Title VI compliant” may appear on the market soon, as manufacturers work to stay ahead of the December 2017 enforcement deadline.

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.

The standard resins used to bind composite wood products are based on formaldehyde compounds.

While these formaldehyde-based compounds themselves present few hazards to occupants, they contain a small amount of unreacted formaldehyde that evaporates over time, contributing significantly to levels of formaldehyde in the home. Urea formaldehyde may degrade throughout its use and hence will continue to emit formaldehyde long after the product's manufacture and installation.

To reduce formaldehyde emissions from their products, manufacturers may use scavenger additives in the resin - such as melamine, hexamine, or various solid ammonium compounds - which bind to the formaldehyde. However, the efficacy of these scavengers may be diminished by hot temperatures, or high humidity. This means that boards containing formaldehyde scavengers installed in a building in the hot, humid American Southeast, with the air conditioner turned off over the weekend, could re-release formaldehyde into the building. Workers could return to the job site on Monday morning and be exposed to large doses of re-emitted formaldehyde.

Last updated: August 11, 2017

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