Flooring Adhesives Hazard Spectrum
Adhesives are required to install many types of flooring. The composition of these products can vary based on their applications, but in general, all adhesives are based on a handful of chemistries, many of which rely on chemicals of concern.
The healthiest adhesive choice is to not use one. Look for products that can be installed with nails or other mechanical fasteners. Avoiding adhesives keeps hazardous chemicals out of interior spaces, and supports the future recycling of those materials at the end of their use because adhesives make some materials unrecyclable.
As a category, adhesive manufacturers tend to reveal little about what’s inside, making it difficult to ascertain which products have hazards, and what their severity may be. Whenever possible, prefer adhesives with Health Product Declarations or other disclosure documents. Absent disclosure, prefer adhesives with very low or zero VOC content.
Mechanical fasteners, such as nails or staples, do not typically contain chemicals of concern. Purchase products that can be installed mechanically, such as wood flooring that is nailed in place.
Peel and stick adhesives are solid-state adhesive strips or squares that adhere some flooring materials to their substrates. They can be factory applied to some products, or be sold separately.
Unlike wet-applied adhesives, peel & stick adhesives are fully reacted and no longer contain reactive substances that would otherwise be released upon application.
To date, the peel and stick flooring adhesives reviewed by Healthy Building Network have had very simple formulations with few hazards. However, manufacturers rarely disclose the specific composition of these adhesives, making a complete assessment difficult.
Glue-down carpet, resilient flooring, and engineered wood flooring manufacturers commonly recommend or require the use of acrylic adhesives. These products are typically water-based, 1-part formulations. The term “acrylic” covers a wide range of chemistries. Adhesives described as acrylic can vary significantly in their formulations. They tend to be low in VOCs, but may contain other hazards.
Because they are water-based, acrylic adhesives likely contain an antimicrobial additive. These antimicrobial additives are not intended to protect the health of occupants, but protect the adhesive from spoiling during storage, or degrading after it has been applied to the underside of a floor. These antimicrobials are typically not disclosed by name, but are considered pesticides by the Environmental Protection Agency. While necessary for these water-based products, some antimicrobials are more hazardous than others.
Specialty acrylic adhesives can contain hazardous flame retardants or additives to make them more resistant to freezing and thawing cycles, so be alert when specifying acrylic adhesives advertising performance attributes beyond what is typical in a more universal product.
Epoxy flooring adhesives are often used to adhere linoleum, vinyl tiles, rubber tiles, or rubber sheets to a variety of flooring substrates. Epoxy chemistries require the use of high hazard substances, including a resin based on bisphenol-A (BPA), nonylphenol ethoxylates (NPEs), and chemicals known as amines which are linked to the onset of asthma. BPA is a reproductive toxicant that has been targeted for removal from children’s products. NPEs are persistent, bioaccumulative toxicants that have been a focus for priority action by EPA for their health effects.
These adhesives come as a two-part system that must be mixed on-site. Once applied, the adhesive must set for 12-72 hours after flooring is installed before it can withstand heavy foot-traffic.
Polyurethane flooring adhesives are often used to install solid or engineered wood, bamboo, parquet, and some rubber and vinyl flooring. These flooring types must be adhered to a concrete substrate in many cases. Polyurethane adhesives are solvent-based and can contain highly toxic tin-based catalysts (PBTs). In addition, polyurethanes contain isocyanates which are potent asthmagens. By touch and through the air, installers and residents may be exposed to these substances as the adhesive is installed and reacts.
Polyurethane adhesives are available in both a one-part moisture cure adhesive or a two-part adhesive that must be mixed together on site. Single component polyurethane adhesives cure using moisture in the ambient air and therefore dry more slowly than 2-part adhesives.
Last updated: August 11, 2017