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The Silicones Industry continues to evaluate the science behind its materials, studying the fate and effects of silicone materials in the environment.  Silicone materials have been subject to hundreds of scientific studies showing that they are safe for the environment, when used for their intended purposes.

Global Environmental Monitoring Initiatives

The Silicones Industry, independent scientific panels, and government authorities in several world regions committed significant resources to better understand the environmental presence and behavior of siloxanes used to make silicones.

These siloxanes are known as octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6). Industry and government-initiated environmental monitoring programs have produced a robust data set that demonstrates that:

  • Siloxanes pose negligible or no risk to the environment
  • No regulatory restrictions are warranted

Global governments are using real-world data to drive chemical assessments. For example, Environment Canada reviewed the scientific data and environmental monitoring results available for D4 and determined that no restrictions were needed on product use or product concentration limits for D4 in any application. Canada’s Minister of the Environment also ruled that no regulatory restrictions on the siloxane known as D5 need to be imposed after it was found by an independent panel of expert toxicologists to pose no risk to the environment now, nor should it pose any risk in the future. Environment Canada also found that D6 did not meet the criteria for listing as a toxic chemical under the Canadian Environmental Protection Act (CEPA) regulation.

Australia reviewed the scientific data and monitoring results available for D4, D5, and D6.  The conclusions reached by their evaluation was in agreement with Canada’s assessment and risk management decisions for these three materials.

Monitoring Initiatives

The Silicones Environmental Monitoring Initiative includes:

  • Long-term monitoring for D4, D5, and D6 in surface sediments and aquatic organisms to determine if concentrations are stable or changing over time
  • Evaluating levels of silicone materials in media from wastewater treatment plants (WWTP) and the aquatic environments receiving direct WWTP effluent

Long-Term Monitoring Program

As part of the industry’s commitment to product stewardship, the Silicones Industry initiated a voluntary long-term monitoring program of D4, D5, and D6 in 2011 to investigate their presence and behavior in the aquatic environment. The long-term monitoring program takes place in four different locations around the world to provide a representative picture of the fate and distribution of siloxanes in both freshwater and marine ecosystems and spanning subtropical to cool temperate climates (Lake Pepin in the United States; Lake Ontario in Canada; Oslofjord in Norway; and Tokyo Bay in Japan). Monitoring has occurred at all 4 sites through 2019.  Monitoring is being conducted in Oslofjord in 2020.

No environmental concentration increase of D4, D5, and D6 has been found over the course of the monitoring program at any location. None of the levels detected posed a risk to aquatic organisms.

United States EPA D4 Monitoring Program

The Silicones Industry worked with the US Environmental Protection Agency (EPA) to design a monitoring program to assess levels of D4 in the environment and produce exposure data the agency needs to conduct a thorough and scientifically sound risk assessment. The final results of the D4 environmental monitoring program were submitted to EPA in September 2017.

An independent peer-reviewed study of the monitoring program data concluded that D4 poses negligible risk to the environment and that no regulatory restrictions for D4 are warranted.

In February, 2020, the industry submitted its request to EPA to conduct a risk evaluation of D4 under the Toxic Substances Control Act (TSCA). In October, 2020, EPA granted the industry request. The industry has been steadfast in its support for risk-based assessments of silicone substances, including D4, and is confident of the safety of D4 for human health and the environment. EPA is expected to finalize the D4 risk assessment by 2024.

European Union Restrictions Monitoring Program

The Silicones Industry implemented a monitoring program to assess the effectiveness of the European Union’s REACH restriction on “wash-off” cosmetic products that targets down-the-drain emissions of D4 and D5 and the proposed restriction on the use of D4, D5, and D6 in leave-on personal care and consumer and professional products. Under the program, the amount of D4, D5, and D6 being released into domestic WWTPs was measured. This monitoring is a surrogate for estimating consumer use of products containing D4, D5, and D6.

Monitoring results indicate that D4 and D6 wastewater treatment plant influent concentrations are well below the baseline levels predicted. For D5, results showed that concentrations are approaching the predicted post-restriction level at all WWTPs. These concentrations are lower than assumed by EU authorities in implementing restrictions and suggest that the restrictions were unnecessary.

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