December 2, 2025
Via Docket (EPA-HQ-OPPT-2018-0443)
Dr. Nancy Beck, Principal Deputy Assistant Administrator
Office of Chemical Safety and Pollution Prevention
U.S. Environmental Protection Agency
1200 Pennsylvania Avenue, NW (MC-7101M)
Washington, DC 20460
Subject: Request for Extension of the Public Comment Period – Octamethylcyclotetrasiloxane (D4) Draft Risk Evaluation Docket ID: EPA-HQ-OPPT-2018-0443
Dear Dr. Beck,
On behalf of National Taxpayers Union (NTU), the nation’s oldest taxpayer advocacy organization, I write to submit the following comments on the EPA’s draft risk evaluation (September 2025) for D4. NTU appreciates the agency’s efforts to assess this chemical under TSCA and to solicit public input. Nonetheless, we must respectfully note our great concern over the preliminary determinations of “unreasonable risk” (or the approach leading to them) on a number of substantive grounds. NTU urges EPA to revise the draft evaluation in multiple respects before moving toward final risk management decisions. Taxpayers have a major stake in ensuring that policies toward D4, as well as the Manufacturer Requested Risk Evaluation (MRRE) process involving D4, are grounded in solid cost-benefit analysis.
As you know, Octamethylcyclotetrasiloxane (D4) is a building block of silicone products, and is the backbone of America’s important silicone industry. As the key intermediate used to produce silicone fluids, elastomers, and resins, D4 anchors a supply chain that reaches virtually every major sector of the modern economy. In fact, D4 is integral in manufacturing electronics, automotive systems, construction materials, all energy technologies, medical devices, aerospace components, and a wide range of everyday consumer products. There are few substitutes that can match silicone’s performance, durability, and versatility at scale.
Because D4 feeds into such a broad production network, it underpins billions of dollars in economic activity and supports America’s manufacturing renaissance. That’s why it is crucial for final rules impacting D4 be thoroughly studied to avoid disruption or overly restrictive regulation that would send ripple effects through industries dependent on silicone-based products. Either of these undesirable outcomes would raise costs for manufacturers and consumers alike.
An unbalanced public policy approach would also weaken U.S. competitiveness in advanced manufacturing, energy development, and high-performance materials, as many cutting-edge technologies rely on stable access to silicone chemistries derived from D4.
Put simply, D4 is not just a chemical intermediate; it is a foundational input that enables high-value industries, supports domestic manufacturing, and strengthens the broader U.S. economy. It has also been safely produced at a commercial scale for over four and a half decades. Yet, for the first time, the agency has concluded that D4 may pose an unreasonable risk to human health and the environment under certain circumstances.
Aside from the market and economic impacts, taxpayers deserve a prominent voice in this conversation. Silicone-based materials last longer, require fewer replacements, and reduce maintenance needs for public facilities, transportation systems, water infrastructure, and energy grids. Fewer repairs and longer asset lifespans directly translate into savings for taxpayers who ultimately fund these systems.
This taxpayer perspective is incredibly important within the health care conversation, since D4-derived silicones are also essential in medical devices, emergency equipment, and public health technologies. Their reliability and stability help keep procurement costs lower over time and ensure hospitals, first responders, and public agencies have access to materials that work in extreme conditions. D4 is also a vital element in parts for vehicle fleets, structures, and other products that governments at all levels purchase on a daily basis. At a time when federal and state government spending on health care issues reaches record highs year after year, silcones help keep taxpayers costs down.
It is also important that EPA solicit and consider scientific evidence from all stakeholders, no matter who presents it. The decision to rely only sporadically on the data gathered by the MRRE does not seem to have much substantiation. Because this is an important test of how a public-private partnership can work in developing efficient and effective regulation, EPA should be more transparent and comprehensive about how this decision was reached and whether some prudent modifications could be made to ensure that this and other MRREs respect that partnership more fully. Otherwise, time and financial resources will be wasted as EPA simply regulates in the dark.
Under the first Trump Administration, an MRRE for D4 was granted by EPA in the fall of 2020 after the silicones industry formulated—in collaboration with EPA—a carefully overseen environmental monitoring program for numerous sites. The data generated from this program—at full expense of the industry—provided the basis for the MRRE and afforded EPA the information it said it needed for a sound scientific evaluation. Yet, today, what should have been a smoothly progressing MRRE has become threatened by uncertainty, which is inimical to a process whose very success depends on the confidence of its participants in a firmly grounded design and the agency’s commitment to following through with established plans. In several contexts, ranging from local-level Extended Producer Responsibility legislation to a federal proposal for pilot reimbursement methods in the 340B pharmaceutical discount program, NTU has offered the D4 MRRE as a model of how the government and private sector can collaborate on regulation in the public interest. We are hopeful that, with a change of course in EPA’s initial Draft Risk Evaluation, the integrity of this model can be affirmed and upheld.
NTU has previously weighed in on this ever-shifting regulatory landscape. For example, at a June 22, 2022, TSCA oversight hearing before the Senate Committee on Environment and Public Works, EPA’s Assistant Director Michal Freedhoff told the panel, “It is incumbent on the agency to do better.” A subsequent coalition of five organizations led by NTU voiced agreement with that statement, and wrote in a letter to then-EPA Administrator Regan: “We would contend that doing better at EPA should be demonstrated before Congress considers major funding increases in this area of the agency’s responsibility. Otherwise, taxpayer resources will be spent for no constructive purpose.” Those words are as true today as they were three years ago—and certainly applicable to the need for EPA to reconsider its Draft Risk Evaluation for D4.
We agree that making progress on environmental, energy, health care, and other goals in a fiscally and economically sustainable manner will require major contributions from and advances in chemical science. The public policy instruments for achieving this progress require thoughtful calibration. We stand ready to assist EPA in fulfilling this vital task, and we thank you for your consideration.
Sincerely,
Thomas Aiello
Senior Director of Government Affairs