In the EU, chemical regulation for cyclics is high.
In 2018, for instance, D4, D5 and D6 were added to a "candidate list of substances of very high concern," and in 2020, restrictions were placed on "wash-off cosmetics" for D4 and D5.
Rinehart noted that the EU is looking to add D6 to the "wash-off cosmetic" list, as well as monomer found in "leave-on" personal care and consumer products.
A proposal to add European Chemicals Agency (a regulatory body formed in 2007) authorization requirements for D4, D5 and D6 monomer was broached in 2020, though that has not yet become law.
"The EU seems to find that the only appropriate risk is zero risk, and this is not feasible in most countries," Rinehart said.
In the U.S., weight-of-evidence guidelines are followed, though they can vary by state.
"Everything we have done both past and current is to follow these guidelines," Rinehart said. "I don't anticipate (any of the current regulations) getting worse (in the U.S.), but different states have their own regulations."
To wit, if states use an EU-based set of parameters, or the ECHA has made a determination affecting their state (as an import), that could be used as a benchmark for disclosing information, she said.
There are no restrictions from Canada on silicone materials.
The country's final screening assessments on D4 determined that it can be "persistent and toxic" to some aquatic organisms, but that "environmental exposure is low."
A Canadian regulatory board also determined that D5 "does not meet regulatory criteria for bioaccumulation," and the overall conclusion noted that D5 "does not pose a danger to the environment now or in the future."
The same conclusion was drawn with D6 monomer, Rinehart said.
"Both hazard and exposure were considered in determination of risk," she said.
South Korea has included the three monomers on its "Priority Control Substance List," but the only requirement is for an end-use manufacturer to report the use for the monomer.
From Brazil to Australia, other non-EU countries differ slightly in their assessments but generally maintain similar regulations to the U.S., Canada and South Korea.
Australia has determined that the three monomer variants do not pose a significant risk to aquatic life, and no restrictions exist on any of the three.
A more complete assessment of silicone monomer is set to be complete in China by the end of the year, Rinehart noted.
And Japan, in 2017, added D4 and D6 to its chemical control law, but the two variants have no restrictions on their use in the country.
"Again, it is worth noting that there are no restrictions on any silicone materials anywhere in the world outside of Europe," she said.
Rinehart said that the Global Silicones Council, a non-profit, international organization representing companies that produce and sell silicone products around the world, has appealed some of the strict EU court determinations on the monomers.
Shin-Etsu is part of this appeal effort, Rinehart said. The ruling is pending before an EU court, according to the GSC website.
Rinehart concluded by stating that silicones are essential to a circular economy, as they exhibit high-energy efficiency in "all observable sectors;" contribute to fuel savings and electrical insulation; and are an "enabler of the renewable energy transition."
In addition, silicones contribute to product longevity and waste reduction, according to Rinehart's presentation.
"The strong contribution to product longevity can also lead to a significant reduction of primary material demand," she said.
Out of all the greenhouse gas benefits, silicones showed the most promise in battery and LED light spaces.
"The future potential can be attributed to the share of electromobility in the passenger car market, expected to increase to 90 percent by 2050," she said.