Sealants

Sealant Product Guidance

Use the red-to-green product guidance below to select safer product types by avoiding those in red and preferring yellow and green, which are safer for occupants, fenceline communities, and workers.

When choosing a sealant product:

Not all sealant types will be suitable for all applications; however, any movement away from red-ranked product types is still a step forward in reducing health impacts.

Here is some general guidance to use when choosing a sealant product:

  • Prefer caulk-type sealants to spray foam sealants. Most spray foam sealants contain asthmagenic isocyanates along with other chemicals of concern.
  • If foam sealing products are needed, prefer those that are pre-formed, like foam sealant tape, instead of a spray foam sealant.
  • For a multi-purpose sealant, look for acrylic, latex, or siliconized latex sealants with very low VOCs - options with ≤ 25 grams per liter (g/L) are available for many applications.
  • Avoid silicone, polyurethane, and hybrid/modified polymer sealants when possible.
    • Where you have to use polyurethane or hybrid/modified polymer sealants, select phthalate-free products. Phthalates (specifically orthophthalates) are common in modified polymer and polyurethane sealants. They may less frequently be found in acrylic, latex, siliconized latex, or silicones. Many phthalates are known endocrine disruptors and have been found to damage reproductive systems and interfere with the normal development of a fetus in the womb. They have also been associated with asthma.
    • When you use silicone sealants avoid those that utilize organotin catalysts and prefer catalysts that are titanium-based. Some organotin compounds, such as dibutyltin dilaurate, have been associated with endocrine disruption.
  • Avoid mold and mildew-resistant products unless necessary.
    • If used, avoid products containing arsenic-based fungicides. Mold- and mildew-resistant products contain fungicides to help prevent mold or mildew growth in damp environments. Ask for disclosure of these chemicals and avoid arsenic containing compounds. Interior locations that are not kitchens or bathrooms should not require mold- and mildew-resistant products.

Pre-compressed polyurethane joint seals are pre-formed, compressed polyurethane foam tapes. These tapes may be used to seal perimeter joints of windows and doors, vertical abutment joints between buildings, and control joints. Polyurethanes do require more hazardous chemical inputs than acrylic latex materials, which can have impacts through chemical and product manufacturing. However, the low density of this product and the fact that they do not react or dry on-site keeps the quantity of hazardous chemicals in this product low relative to other products in this guidance. 

Though uncommon, some products may contain halogenated flame retardants like TCPP, a persistent and bioaccumulative toxicant. Avoid these chemicals by requiring manufacturers to disclose the identity of any flame retardants. Preferring products containing non-halogenated flame retardants. 

Acrylic and latex sealants are water-based and non-reactive when installed. They can be used for many exterior and interior applications. While the primary components of these sealants are non-hazardous, some common additives have associated health hazards. Examples include ethylene glycol, a developmental toxicant, and Stoddard solvent, a carcinogen and mutagen.

When compared to other types of sealants, acrylic and latex sealants tend to contain fewer chemicals of concern, but some may contain phthalate plasticizers that are known endocrine disruptors. Identify and select phthalate-free products by requiring the manufacturer to disclose the type of plasticizers used. In addition, prefer those with very low VOC content, ≤ 25 g/L.  

Siliconized latex sealants are a variation of standard latex sealants. They are used in interior and exterior applications such as around window trims, filling gaps in windows and doors, and sealing kitchen and bathroom fixtures. In these formulations, manufacturers add small proportions of silicone fluid or silanes to enhance adhesion under wet conditions. Unlike silicone sealants which are chemically cured, siliconized latex sealants cure from evaporation of water. Like other latex sealants, some products contain ethylene glycol, a developmental toxicant, as antifreeze. 

Preservatives and surfactants are required in water-based products but are often not disclosed. Products can contain small amounts of carcinogenic preservatives, such as chlorothalonil, or octylphenol ethoxylate surfactants. Octylphenol ethoxylates are part of the alkylphenol ethoxylate (APE) chemical group, which are a priority to avoid. Look for very low VOC (≤ 25 g/L) products and make sure that the products you use are phthalate-free.

Acoustical sealants are typically acrylic or latex-based and are non-hardening sealants  used to fill gaps in flooring, walls, and ceiling systems. They are designed to manage sound leakages while maintaining sound transmission ratings (STC). 

Acoustical sealants have a similar composition to other acrylic or latex sealants and may contain ethylene glycol, a developmental toxicant, as antifreeze. Plasticizers are not always disclosed. Identify and select phthalate-free products by requiring the manufacturer to disclose the type of plasticizers used and prefer products with very low VOC content, ≤ 25 g/L.

Note that some butyl acoustical sealants are available, sometimes referred to as "non-skinning." These would fall into the Butyl Sealant ranking below.

Butyl sealants are used in flashing, chimneys, sealing gutters, and downspouts. They are solvent-based and cure as the solvent evaporates, which can expose installation teams and people nearby to hazardous chemicals. These chemicals typically include large amounts of Stoddard solvent, which is a carcinogen and mutagen. Butyl sealants can also contain smaller amounts of other solvents including ethylbenzene, another known carcinogen.

The base material that forms the seal is butyl rubber, which has more hazardous chemicals of concern during the manufacturing process when compared to acrylic and latex products. 

Single-component silicone sealants are used for a variety of interior and exterior applications, including structural glazing and weatherization. All products cure upon application in the presence of moisture. This curing process releases different chemicals depending on the product. Acetoxy cure systems release acetic acid, while the most common neutral curing systems release either methyl ethyl ketoxime, a carcinogen, or methanol, a developmental toxicant.

Cyclosiloxanes, which are persistent and bioaccumulative toxicants (PBTs), are used to manufacture silicones, and contain up to 1% of these hazardous chemicals.[1] Silicones have more hazardous chemical concerns during manufacturing than most other base materials used in sealants because of these PBTs.

If silicone sealants must be used, avoid formulations with organotin catalysts like dibutyltin dilaurate, a reproductive toxicant. Prefer those with titanium-based catalysts.

Single-component polyurethane spray foam products come in many varieties for specific applications, such as filling gaps around door and window frames to seal against air and sound infiltration. They are reacted on-site and can release isocyanates, which are potent respiratory sensitizers. Organizations like the U.S. Occupational Safety and Health Administration (OSHA) have identified isocyanates as a leading cause of work-related asthma. Anyone installing reactive sealants based on isocyanate chemistry may become exposed by touch or inhalation.[2] Halogenated flame retardants are also common and are a very high concern to avoid because they can be persistent and toxic.[3] 

Polyurethane requires more hazardous chemical inputs than acrylic latex materials, which can have impacts through chemical and product manufacturing. Because less material is needed to fill a given volume than for other polyurethane sealants, their overall impact is slightly smaller, but they are still not a preferred material.

Hybrid or modified polymer sealants, sometimes called silyl-terminated polyether (STPE) sealants, are single-component, moisture-cured sealants. They can be used to seal interior and exterior gaps including siding and around windows and doors. While often touted as environmentally-friendly, being free of solvents and isocyanates, products commonly contain organotin catalysts and around 15% phthalates. Some organotins are reproductive toxicants, and many phthalates are known endocrine disruptors and reproductive toxicants. Phthalates have also been associated with asthma. In addition, methanol, a developmental toxicant, is emitted as these products cure. The base materials used in these sealants have more hazardous chemical inputs than acrylic latex materials, which can have impacts through chemical and product manufacturing.

If using a modified polymer sealant, specify those that have fully disclosed contents and use non-phthalate plasticizers, like polypropylene glycol.

Mildew resistant and sanitary silicone sealants are one-component products that are commonly used in interior damp environments such as locker rooms and lavatories, and applied to bathtubs, shower stalls, sinks, countertops, and other plumbing fixtures. They contain fungicides to impede mold and mildew growth in damp environments.[4] Some antimicrobials are known to have adverse health impacts, and due to their potential to contribute to antimicrobial resistance, mildew-resistant and sanitary silicone sealant use should be limited to damp environments. Like other silicone sealants, these products contain persistent, bioaccumulative toxicants (PBTs), cyclosiloxanes. Many mildew-resistant silicone sealants are acetoxy-curing. These products release acetic acid upon curing rather than the hazardous chemicals associated with their neutral curing counterparts. 

Mildew-resistant silicone sealants are ranked lower than other silicone sealants because they commonly contain a petroleum distillate plasticizer that is a persistent and bioaccumulative toxicant. Arsenic-based fungicide can be used in some products. Arsenic is considered a persistent and bioaccumulative toxicant.  

The base materials used in silicones have more hazardous chemical concerns during manufacturing than those used in most other sealants because silicones are made from cyclosiloxanes, which are PBTs. Ask for products free of arsenic-based fungicides for applications where a mildew-resistant silicone sealant is required.

Single-component polyurethane sealants can be used in interior or exterior joint sealing applications such as expansion and control joints, siding gaps, gaps around perimeters of doors and windows, and other wall penetrations. They cure with moisture in the air when applied and commonly contain the isocyanates TDI and MDI. Isocyanates are potent respiratory sensitizers and have been identified as a leading cause of work-related asthma.[5] Single-component polyurethane sealants can contain a number of hazardous chemicals such as phthalate plasticizers, that are known developmental toxicants, and organotin catalysts like dibutyltin dilaurate, a reproductive toxicant. Also common are hazardous solvents including xylenes, which are developmental toxicants, and ethylbenzene, a carcinogen.

One-component polyurethane sealants commonly contain a high percentage of polyvinyl chloride (PVC). PVC production can have greater impacts on workers and fenceline communities since it requires the use of more hazardous chemicals than other plastics. 

Two-component polyurethane sealants can be used in interior or exterior joint sealing applications such as expansion and control joints, siding gaps, gaps around perimeters of doors and windows, and other wall penetrations. They contain a polyol part A and an isocyanate part B, which are mixed prior to application. Two-part polyurethane sealants contain higher levels of unreacted isocyanates than one-part systems. Isocyanates are potent respiratory sensitizers and have been identified as a leading cause of work-related asthma.[6] Similar to one-component systems, two-component polyurethane sealants can contain phthalate plasticizers that are known developmental toxicants. Dibutyltin dilaurate, an organotin catalyst and reproductive toxicant, is common in two-component polyurethane sealants. 

Also common in these sealants are hazardous solvents including xylenes, which are developmental toxicants, and ethylbenzene, a carcinogen. Polyurethane requires more hazardous chemical inputs than acrylic latex materials, which can have impacts through chemical and product manufacturing.

Supporting Information

Unless otherwise noted, product content and health hazard information is based on research done by Habitable for Common Product profiles, reports, and blogs. Links to the appropriate resources are provided.

Common Product Records Sourced

Endnotes

[1] Environment Canada, Health Canada. “Screening Assessment for the Challenge: Octamethylcyclotetrasiloxane (D4).” Health Canada, November 2008. https://www.ec.gc.ca/ese-ees/default.asp?lang=En&n=2481B508-1. 

[2] While reported incidents have declined in recent years, limited data are available to gauge the scope of the issue. Rosenman, Kenneth D., Mary Jo Reilly, and Barton G. Pickelman. “2019 Annual Report Tracking Work-Related Asthma in Michigan.” Michigan State University, July 20, 2020. https://oem.msu.edu/images/annual_reports/2019-WRA-Annual-Report-FINAL.pdf.; The National Institute for Occupational Safety and Health (NIOSH). “Work-Related Asthma: Exposures Most Frequently Reported by Work-Related Asthma Cases in California, Massachusetts, Michigan, and New York, 2009–2014.” Centers for Disease Control and Prevention (CDC), November 2020. https://wwwn.cdc.gov/eWorld/Grouping/Asthma/97.

[3] “TSCA Work Plan Chemical Problem Formulation and Initial Assessment: Chlorinated Phosphate Ester Cluster Flame Retardants.” US EPA, Office of Chemical Safety and Pollution Prevention, August 2015. https://www.epa.gov/sites/production/files/2015-09/documents/cpe_fr_cluster_problem_formulation.pdf.

[4] Coffin, Melissa, Tom Lent, Susan Sabella, Jim Vallette, Bill Walsh, Mary Dickinson, Suzanne Drake, Robin Guenther, Max Richter, and Brodie Stephens. “Healthy Environments: Understanding Antimicrobial  Ingredients in Building  Materials.” Healthy Building Network, Perkins+Will, March 2017. https://healthybuilding.net/reports/4-healthy-environments-understanding-antimicrobial-ingredients-in-building-materials.; Healthy Building Network, Green Science Policy Institute, Perkins&Will, International Living Future Institute, and Health Product Declaration Collaborative. “Joint Statement on Antimicrobials in Building Products,” March 31, 2021. https://www.mindfulmaterials.com/antimicrobials-letter.; Ben Maamar, Sarah, Jinglin Hu, and Erica M. Hartmann. “Implications of Indoor Microbial Ecology and Evolution on Antibiotic Resistance.” Journal of Exposure Science & Environmental Epidemiology 30, no. 1 (October 7, 2019): 1–15. https://doi.org/10.1038/s41370-019-0171-0.

[5] US Occupational Safety and Health Administration. “OSHA Fact Sheet: Do You Have Work-Related Asthma? A Guide for You and Your Doctor,” March 2014. https://www.osha.gov/Publications/OSHA3707.pdf.; Rosenman, Kenneth D., Mary Jo Reilly, and Barton G. Pickelman. “2019 Annual Report Tracking Work-Related Asthma in Michigan.” Michigan State University, July 20, 2020. https://oem.msu.edu/images/annual_reports/2019-WRA-Annual-Report-FINAL.pdf.; Lefkowitz, Daniel, Elise Pechter, Kathleen Fitzsimmons, Margaret Lumia, Alicia C. Stephens, Letitia Davis, Jennifer Flattery, et al. “Isocyanates and Work-Related Asthma: Findings from California, Massachusetts, Michigan and New Jersey, 1993-2008.” American Journal of Industrial Medicine 58, no. 11 (November 2015): 1138–49. https://doi.org/10.1002/ajim.22527.; US Environmental Protection Agency. “Methylene Diphenyl Diisocyanate (MDI) and Related Compounds Action Plan [RIN 2070-ZA15],” April 2011. https://www.epa.gov/sites/production/files/2015-09/documents/mdi.pdf.

[6] US Occupational Safety and Health Administration. “OSHA Fact Sheet: Do You Have Work-Related Asthma? A Guide for You and Your Doctor,” March 2014. https://www.osha.gov/Publications/OSHA3707.pdf.; Rosenman, Kenneth D., Mary Jo Reilly, and Barton G. Pickelman. “2019 Annual Report Tracking Work-Related Asthma in Michigan.” Michigan State University, July 20, 2020. https://oem.msu.edu/images/annual_reports/2019-WRA-Annual-Report-FINAL.pdf.; Lefkowitz, Daniel, Elise Pechter, Kathleen Fitzsimmons, Margaret Lumia, Alicia C. Stephens, Letitia Davis, Jennifer Flattery, et al. “Isocyanates and Work-Related Asthma: Findings from California, Massachusetts, Michigan and New Jersey, 1993-2008.” American Journal of Industrial Medicine 58, no. 11 (November 2015): 1138–49. https://doi.org/10.1002/ajim.22527.; US Environmental Protection Agency. “Methylene Diphenyl Diisocyanate (MDI) and Related Compounds Action Plan [RIN 2070-ZA15],” April 2011. https://www.epa.gov/sites/production/files/2015-09/documents/mdi.pdf. 

Last updated: September 27, 2022