Toxic Phthalates in Sealants: Hidden Risks And The Push For Safer Building Materials

Sealants are ubiquitous in homes, schools, and workplaces, yet they rarely cross most people's minds. Though they blend into the background of daily life, these unassuming materials can have a detrimental effect on indoor air quality and human well-being.

In building construction, sealants serve a critical purpose: sealing gaps and controlling airflow, a function that has grown even more important amid the current climate crisis. Regrettably, despite their widespread use, many sealants contain hazardous chemicals such as isocyanates and phthalates. These semi-volatile compounds can off-gas from sealants over time, polluting indoor air and settling into household dust.

Phthalates are known to disrupt the body's hormonal balance and are associated with reproductive harm. While some phthalates have been prohibited in children's products at both the federal level and in states like Washington, California, and Vermont, vulnerable groups-including children and pregnant individuals-still face exposure from numerous sources, including common building materials like sealants.

Currently, the Washington Department of Ecology is putting forward a rule to ban phthalates in vinyl flooring and fragrances in personal care items. Scientific studies have confirmed that indoor air and household dust are major pathways for phthalate exposure, making these regulations a crucial step toward reducing harm.

Aware of the dangers posed by phthalates and the role building materials play in exposing people to these toxins, Toxic-Free Future collaborated with the Healthy Building Network and the Ecology Center of Michigan in 2021 and 2022 to conduct phthalate testing on sealants. This initiative builds on previous work with the Ecology Center and other partners to eliminate phthalates from retail vinyl flooring and supports ongoing regulatory efforts in Washington state.

For this new study, the team purchased and analyzed 33 sealant products-including polyurethane, silicone, and acrylic latex varieties-commonly used in construction and renovations, which were suspected of containing phthalates. Staff at the Ecology Center used a Fourier-transform infrared (FTIR) spectrometer to screen for phthalates, and additional laboratory testing was commissioned for products that tested positive.

The results revealed that six out of the 33 tested sealants contained high concentrations of phthalates-up to 12% by weight-including both diisononyl phthalate (DINP) and diisodecyl phthalate (DIDP). Notably, phthalates were most commonly found in "silane modified polymer" sealants: five out of the seven such sealants tested positive. Importantly, the remaining 27 products had no detectable phthalates, demonstrating that safe alternatives are already available.

Many sealant manufacturers have already stopped using phthalates, and it is essential that all sealants are produced without these harmful chemicals. Safer alternatives to phthalate-containing sealants exist, such as sodium silicate caulk and pre-compressed polyurethane joint seals.

The Big Picture: Healthy Buildings Depend on Healthy Materials

Toxic Building Materials Extend Beyond Sealants

Sealants are just one example of building materials that contain toxic ingredients, contributing to poor indoor air quality and health risks. From paint and flooring to insulation, numerous other building materials often include chemicals that can harm human health-and in every case, safer alternatives are available.

Affordable Housing Residents Face Disproportionate Exposure

Research shows that the burden of toxic building materials is not shared equally. Residents of affordable housing are disproportionately exposed, as these units are often constructed using cheaper materials that may contain higher levels of toxins-putting residents' health at risk.

Beyond greater exposure through their homes, affordable housing residents are also more susceptible to the harms of toxic chemicals. In a report on the high concentration of affordable housing near Superfund sites, the Shriver Center on Poverty Law notes: "the five million total families who live in federally assisted housing are predominately comprised of the people most vulnerable to exposure to environmental toxins." This includes large numbers of children, individuals with disabilities, older adults, and Black and Latine communities.

Toxic building materials have long-lasting impacts, especially in affordable housing. For instance, even though lead paint was banned in 1978, it continues to harm children living in affordable housing today. More than 90,000 children in Housing Choice Voucher (Section 8) housing suffer from lead poisoning, which causes permanent damage to brain development.

Now Is the Time for Policies That Mandate Safer Building Materials

To protect human health and safety, building materials must be free of toxic chemicals. Organizations like Enterprise Green Communities and the Healthy Building Network, along with state programs such as Safer Products for Washington (SPW), have been at the forefront of the movement for safer building materials. Enterprise Green Communities advocates for healthy materials in affordable housing developments, identifying phthalates in sealants and other toxins in building products as critical health concerns. The organization has developed criteria that builders nationwide can meet to earn accreditation for using safer materials in affordable housing.

The Healthy Building Network also works to eliminate toxic chemicals in building materials, conducting extensive research on chemical hazards and safer alternatives. Its HomeFree Product Guidance ranks building materials on a scale from red to green based on the hazard level of their contents and suggests safer options, offering a valuable resource for anyone seeking healthier building materials.

In Washington state, Toxic-Free Future has advocated for strong restrictions on toxic chemicals, but the Department of Commerce has failed to adequately protect affordable housing residents with its version of the Enterprise standards. Programs like Safer Products for Washington are also taking action on toxins like phthalates in building materials. Every five years, Washington's Department of Ecology regulates a set of toxic chemicals, banning or limiting their presence in consumer products. This innovative program protects people and the environment by regulating thousands of chemicals and the products they appear in. While the Ecology Department initially focused on restricting phthalates in vinyl flooring, it must expand these restrictions to ensure all building materials are free of harmful chemicals. Given the presence of phthalates in our sealant testing, the Ecology Department should ban phthalates in sealants in its next round of regulations.

Home Improvement Chains Must Ban Phthalates in Sealants

Our new testing highlights the urgent need for major home improvement chains like The Home Depot and Lowe's to ban ortho-phthalates and other toxic chemicals in sealants. Both retailers have already demonstrated leadership by eliminating phthalates in vinyl flooring; they should build on this progress by removing phthalates from sealants and other building products, which-like flooring-can contaminate indoor environments. These retailers should also ensure that the alternative products are proven safer, meeting standards such as GreenScreen Benchmark 2 or ChemFORWARD C criteria or higher.

Everyone deserves healthy places to live and work. Now is the time to build on national standards like Enterprise Green Communities to ensure affordable housing is safe and healthy for all residents. Retailers like The Home Depot and Lowe's have already shown that safer alternatives exist by eliminating phthalates in vinyl flooring, and they must continue to ban toxins in other products. In Washington state, the Department of Ecology should use the Safer Products for Washington program to ban toxic chemicals in all building materials.