Lauren Ellis, Research Analyst, Environmental Health

Earlier this week, EDF submitted comments to EPA on the agency’s draft scope for the manufacturer-requested risk evaluation of D4 under the Toxic Substances Control Act (TSCA). This is EPA’s first draft scope under the Biden Administration – providing an opportunity to see where improvements have been made and where challenges still exist (see EDF’s and others’ comments on the last set of draft scopes under the Trump Administration).

In our comments, we applaud the agency for developing a more comprehensive chemical risk evaluation plan than EPA provided in past scopes. For instance, in its draft scope document, EPA indicated its intent to assess exposure occurring via environmental release to capture fenceline exposures – a necessary step toward addressing environmental justice considerations under TSCA. EPA also indicated it would not assume the use of personal protective equipment (PPE) when evaluating and making determinations on potential risks to workers – a highly problematic approach taken in the past. However, the draft D4 scope also revealed areas still needing further improvement, including greater detail on how the agency will approach differential risks across the population and address combined exposures from different sources.

Last year, the Silicones Environmental, Health and Safety Center (SEHSC), on behalf of Dow Silicones Corporation, Elkem Silicones USA Corporation, Evonik Corporation, Momentive Performance Materials, Shin-Etsu Silicones of America, Inc., and Wacker Chemical Corporation, asked EPA to evaluate D4, or octamethylcyclotetrasiloxane, under TSCA’s provisions governing manufacturer-requested risk evaluations. In October 2020, EPA granted that request. Critically, when conducting manufacturer-requested risk evaluations, EPA must adhere to the same requirements under TSCA as EPA-initiated risk evaluations, including consideration of all reasonably available information and use of the best available science.

D4 is a high production cyclic siloxane chemical, with an annual U.S. production volume of 750 million to 1 billion pounds. It has widespread industrial, commercial, and consumer uses, including as a reactant to make other silicone chemicals; in adhesives, paints, and plastic products; and in food packaging, personal care products (e.g., hair, skin, and nail products), over-the-counter medications (e.g., anti-gas drugs), and medical devices (e.g., breast implants).

D4 hazard, exposure, and risk has been considered by the Government of Canada and the European Chemicals Agency, among others. In 2009, a Health Canada screening assessment concluded that D4 is harmful to the environment and its biodiversity. In Europe, D4 is currently restricted in wash-off cosmetics (concentration limit of 0.1 % w/w); and recently, the European Chemicals Agency proposed further restrictions on D4 in other consumer and commercial uses due to potential risk. Notably, here in the U.S., EPA has received 39 separate “substantial risk reports” on D4 under TSCA Section 8(e), highlighting health concerns such as reproductive toxicity and immunotoxicity. Given the results of previous risk assessments on D4, and the significant number of risk reports provided to the agency, EPA must comprehensively assess the potential risk of D4 in all relevant uses to best protect public health.

Despite EPA’s movement toward a more comprehensive, public health protective approach to risk evaluation (see EDF’s Re-visioning TSCA after the Trump years blog series), the draft D4 scope highlights significant issues that remain, including:

• Insufficient indication of specific “potentially exposed and susceptible subpopulations” that will be included in the risk evaluation;
• Absence of a revised systematic review method and a specific systematic review protocol for D4;
• Inadequate plan to use information authorities under TSCA to fill the extensive data gaps identified;
• Failure to consider combined exposures to D4 in the workplace (e.g., when a worker is engaged in multiple activities involving potential exposure to D4);
• Failure to consider combined exposures to individuals who fall into multiple receptor categories (e.g., individuals exposed to D4 in both the workplace and as resident of a fenceline community);
• Insufficient commitment to consider relevant “background exposures” of D4 that may fall outside of TSCA’s direct regulatory authority but are relevant to evaluating risks from “TSCA uses” (e.g., exposures from food packaging, personal care products, and medical applications); and
• Insufficient detail on how EPA plans to assess and incorporate uncertainty associated with the use of modeled or surrogate data when evaluating potential D4 risk.

EDF commends EPA for improvements made from previous scopes, and urges the agency to address the identified deficiencies in the final D4 scope.

See EDF’s comments for more detail.