Chemicals in spray polyurethane foam: How can something so toxic be considered green?

2021-11-25 08:10:41 By : Ms. June Li

Spray polyurethane foam is widely promoted as a green building material because of its ability to improve energy efficiency. The insulation effect per inch is better than fiberglass or cellulose, which means that a lot of energy can be saved in heating and cooling. However, energy efficiency is not the only consideration for sustainable buildings. If you carefully observe the chemical composition of the spray foam, you can find many known harmful substances.

Spray polyurethane foam consists of two liquid chemical components, called "A side" and "B side", which are mixed at the installation site. Side A is mainly composed of isocyanate, while side B usually contains polyols, flame retardants and amine catalysts. These chemicals produce harmful fumes during the application process, which is why installers and nearby workers should wear personal protective equipment during this process. Once the foam is fully expanded and dried, the manufacturer will say it is inert. If the chemicals are not properly mixed, they may not react completely and remain toxic.

The risks associated with side A isocyanates have been relatively well documented, but the risks associated with side B are less well known. Since 2010, David Marlow of the Centers for Disease Control has been studying the exhaust problems associated with spray foam installation. Although Marlow could not be interviewed, the CDC Office of Public Affairs was able to provide information about his ongoing research via email. These field studies are aimed at determining the exposure of all chemical components of spray foam, determining a better understanding of the curing rate and determining the safe re-entry time, and developing engineering controls to reduce exposure risks. In addition to the hazards associated with installation, these chemicals may also remain unreacted in the form of dust or shavings. The Environmental Protection Agency warns that “cutting or trimming the foam when it hardens (without the sticky phase) may generate dust that may contain unreacted isocyanates and other chemicals.” This is also a problem in the foam removal process.

Isocyanates, such as methylene diphenyl diisocyanate (DMI), are present in the "A side" of the spray foam mixture. Isocyanates are also found in paints, varnishes and other types of foam. They are known causes of occupational asthma. According to Dr. Yuh-Chin T. Huang, a professor at Duke University Medical Center, isocyanate-induced asthma is similar to other types of asthma, but it is not triggered by exercise, but by exposure. Once someone becomes sensitive, re-exposure can cause a severe asthma attack.

The homeowner, Keri Rimel, said that both she and her husband became extremely sensitive after they were exposed to isocyanates and other chemical odors during the spray foam installation. "To this day, he can still walk into any restaurant, home or office, and he can immediately determine whether there is spray foam in the building," says her husband's Rimel.

According to the CDC, direct contact with isocyanates can also cause rashes if they come in contact with the skin.

Amine catalysts are one of the side B chemicals that CDC is studying for the purpose of understanding the exposure level during installation. "The amine catalysts in [spray polyurethane foam] may be sensitizers and irritants that can cause blurred vision (halo effect)," they wrote.

According to a report issued by the Consumer Product Safety Commission, amine catalysts can also irritate the eyes, skin and respiratory system, and if ingested, "may also cause reversible effects called glaucoma, blue haze or eye halo."

It was also found on side B that polyols are alcohols used as catalysts. Polyols are usually made from adipic acid and ethylene glycol or propylene oxide. Some polyols are made from soybeans, but according to the Pharos project, an organization that promotes transparency in building materials, soy-based materials account for only 10% of the final insulation material.

Ethylene glycol is a chemical used to produce polyols in some spray foams. In the case of acute exposure (such as swallowing), it can cause vomiting, convulsions and affect the central nervous system. According to the US Environmental Protection Agency, inhalation exposure can cause irritation of the upper respiratory system.

A flame retardant is added to the B side to pass the flammability test in the building code. The main flame retardants used in spray foam are hexabromocyclododecane (HBCD or HBCDD) and tris(1-chloro-2-propyl) phosphate (TCPP).

According to the Centers for Disease Control, “flame retardants, such as halogenated compounds, are persistent bioaccumulative and toxic chemicals.” Bioaccumulation means that a chemical substance accumulates in the body faster than it is discharged , So even if the exposure level is very low, there may be a risk of chronic poisoning. These chemicals also accumulate in the ecosystem and enter the food chain. A paper published by Vytenis Babrauskas in the "Architectural Research and Information" magazine stated, "The content of flame retardants, which are mainly used for building insulation, is found in household dust, human body fluids and the environment." The paper also cited Several other studies have shown that these chemicals are related to endocrine disorders and are potentially carcinogenic.

In a CDC post, Marlowe described the composition of side B as a "chemical question mark." He described the necessity of "real world sampling".

In addition to those listed above, other undisclosed and protected trade secret chemicals may be used in the spray foam. This is especially disturbing for homeowners who want to conduct an air test because they don’t know which tests to perform. "You have to tell the tester what you are looking for," said Terry Pearson Curtis, an expert on indoor air quality. "Many times the problem is trying to figure out what you are looking for."

"Potential chemical exposure of spray polyurethane foam." Environmental Protection Agency.

"Isocyanates." Centers for Disease Control and Prevention.

Lefkowitz, Daniel and others. "Isocyanates and work-related asthma: California, Massachusetts, Michigan, and New Jersey survey results, 1993-2008." American Journal of Industrial Medicine, Vol. 58, no. 11, 2015, pp. 1138-1149., doi:10.1002/ajim.22527

Marlowe, David, De Capit, Joseph and Garcia, Alberto. "The spraying of polyurethane foam chemicals during the spraying process exposes all about the children, Crestwood, Kentucky." Centers for Disease Control and Prevention.

"Status report: employee review of five amine catalysts in spray polyurethane foam." Consumer Product Safety Commission.

"Spraying polyurethane foam: an explosive problem." Healthy Building Network.

"Ethylene Glycol: Systemic Drugs." Centers for Disease Control and Prevention.

"Ethylene Glycol." Environmental Protection Agency.

Babrauskas, Vytenis, etc. "Flame Retardants in Building Insulation Materials: A Case for Reassessing Building Codes." Building Research and Information, Vol. 40, no. 6, 2012, pp. 738-755., doi:10.1080/09613218.2012.744533

Marlow, David A. "Help needed: spray polyurethane foam insulation research." Centers for Disease Control and Prevention.

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