The silicones industry is committed to the responsible use of silicones and international environmental stewardship. The industry continues to evaluate the science behind its materials, and monitor the presence of substances in the environment through robust environmental monitoring programs.

To provide the U.S. Environmental Protection Agency (EPA) with environmental monitoring data on one of the basic substances used to make silicones, the siloxane D4, in March 2016 members of the SEHSC began an environmental monitoring program, designed in partnership with EPA, to assess levels of D4 in the environment. In September 2017, members of SEHSC submitted the final results of its D4 environmental monitoring program to EPA. An independent peer-reviewed study of the monitoring program concluded that D4 does not harm the environment and that no further 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 needed to be imposed on product use or product concentration limits for the use of 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, or in the future. Environment Canada found D6 did not meet the criteria for listing as a toxic chemical under the Canadian Environmental Protection (CEPA) regulation.

Long-range transport

Long-range transport (LRT) is the term used to describe the movement of chemicals through air, water and animals.  LRT becomes problematic only when the chemical transported has some adverse impact on human health or on ecosystems far from its source.

The LRT potential of cyclic volatile methylsiloxanes (cVMS) has been considered by regulatory authorities and scientists around the globe. cVMS have the potential to undergo LRT to remote regions via the atmosphere, because their half-lives are longer than two days.  However, they do not back-deposit in remote regions, as they are readily degraded in air. As a consequence, only a small fraction of cVMS may reach the remote parts of the atmosphere. For example, the measured cVMS concentrations in the Arctic air are hundreds of times lower than those in the source region. 

The conclusion that cVMS will not deposit to the terrestrial environment of remote regions, regardless of their half-lives in the atmosphere, is further supported by multimedia modeling assessments (Xu and Wania, 2013) using the OECD overall persistence and long-range transport screening tool (Wegmann et al., 2009) and the GloboPOP model (Wania, 2006). 

Monitoring Initiatives

As part of the industry’s commitment to product stewardship, the silicones industry initiated a Monitoring Program for D4 and D5 in 2010. The Silicones Monitoring Program takes place in four different locations around the world to provide a representative picture of the silicone materials’ fate and distribution, i.e. Lake Pepin in the United States; Lake Ontario in Canada; Oslofjord in Norway; and Tokyo Bay in Japan.

The Silicones Monitoring Program consists of three main parts:

  • Evaluating emissions from wastewater treatment plants (WWTP) by determining the effectiveness of WWTP and the representative concentrations of D4 and D5 releases;
  • Long-term monitoring program for D4 and D5 in surface sediment and aquatic biota to determine if concentrations are stable or changing over time; and,
  • State-of-the-art modelling techniques for accurate predictions of a large number of similar locations.