Industry, Activists Diverge on ‘Best Science’ Under Toxics Law

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By Pat Rizzuto

The EPA must define terms like “best available science” mandated by its chemicals statute so the regulated community can understand how the agency will analyze the risks of chemicals companies make or use, trade associations said.

“Definitions give better insight into how EPA would conduct its assessments, and that additional insight gives much better clarity about how to prepare,” Karyn Schmidt, senior director for chemical regulation, regulatory and technical affairs at the American Chemistry Council, told Bloomberg BNA.

“It is the government’s duty to spell out the foundations of its decisions and clarify compliance criteria. It is a question of fundamental fairness,” Jack Snyder, executive director of the Styrene Information & Research Center, told Bloomberg BNA.

But environmental groups and some states say any rigid definition in the Environmental Protection Agency’s pending risk evaluation rule would not capture evolving scientific research and approaches. They want the agency to issue nonbinding guidance documents instead.

Richard Denison, lead senior scientist with the Environmental Defense Fund, and Jennifer McPartland, a health scientist with the fund, told Bloomberg BNA that defining such terms in regulations could mean the EPA would lock in analytic methods that are out of date or still disputed within the scientific community.

Regulatory definitions run the risk of limiting science to what may be best today “when at some point in the future there will be a much better way to do that,” Jack Fowle, a former EPA scientist, told Bloomberg BNA.

It may be possible, however, to include principles of what constitutes best available science—such as the need for transparency—into regulations, said Fowle, who runs Science to Inform, a consulting firm focused on emerging toxicity testing methods and other topics.

Regardless of whether the 2016 Toxic Substances Control Act’s science mandates are defined in regulations or guidance, lawsuits are likely to be filed in courts that will weigh in on whether or not the agency has complied, Daniel Rosenberg, a senior attorney with the Natural Resources Defense Council, told Bloomberg BNA.

Proposed Rule

At issue is the EPA’s Jan. 19 proposed rule (RIN: 2070-AK20) laying out the procedures by which the agency would evaluate chemical risks (82 Fed. Reg. 7562).

This is the third “framework” rule mandated by the 2016 Toxic Substances Control Act amendments. Together the three rules would require the EPA to assess the safety of chemicals in commerce, something the original TSCA never required it to do.

The three rules would establish the agency’s procedures to determine which chemicals have been in commerce, sort through them to flag ones raising possible health concerns and identify ones that do not.

The EPA then would evaluate the risks of high-priority chemicals. If its evaluations determine that a chemical poses unreasonable risks to people or the environment, then those chemicals would be regulated.  

Science Requirements

Companies up and down the chemical supply chain split from state regulators, physicians groups, environmental health organizations and some water utilities on the question of whether the EPA should define scientific terms and practices mandated by the TSCA amendments in the risk evaluation and other framework rules.

Section 26 of the 2016 TSCA amendments requires the EPA to:

  •  “use scientific information, technical procedures, measures, methods, protocols, methodologies, or models, employed in a manner consistent with the best available science;”
  •  decide whether toxicity or other chemical tests are needed and evaluate the risks of both new and existing chemicals “based on the weight of the scientific evidence;” and
  •  make its determinations and scientific information available to the public.
The EPA did not define the terms “best available science” or “weight of evidence” in its proposed rule—phrases that have drawn controversy in past debates about toxic risks.

“Codifying a specific definition can inhibit the flexibility of the agency to quickly adopt and implement changing science,” the EPA said in its proposed rule.

Similar Requirement in Water Law

Rita Schoeny, a private consultant and retired senior science adviser for the agency’s Office of Water, told Bloomberg BNA that the agency used the same rationale in the 1990s when it defined “best available, peer-reviewed science” in the 1996 Safe Drinking Water Act amendments.

Science evolves quickly, she said and if an agency wants to foster good—yet consistent—use of science it uses guidance to explain how.

For example, the EPA’s peer review handbook has been updated four times as practices change and as the agency gains experience in using contractors and addresses conflicts of interest when forming panels, she said.

“Guidance is the easiest to adapt—even that won’t change overnight. It will be submitted to a lot of scrutiny and peer review,” Schoeny said.

Existing Guidance Found Lacking

The EPA’s existing guidance documents, however, do not provide clear definitions for terms such as “best available science,” “weight of evidence,” or “sufficiency of information,” the American Chemistry Council said in its comments.

The council suggested definitions of those three terms along with “unreasonable risk” and “reasonably available information.”

Other trade associations including the Styrene center and Toy Industry Associations Inc., backed the chemistry council’s suggested definitions.

None of the definitions would require using specific methods to assess chemicals, or “’freeze” the science, Schmidt said.

“Indeed, best available science depends on the converse,” the council said. “Scientific advancements will be important to ensuring the effective and efficient implementation” of the TSCA amendments, it said.

Margins of Exposure

Yet in interviews with Bloomberg BNA, environmental health researchers and organizations said the council’s definitions would constrain the use of scientific advances.

They pointed to the chemistry council’s definition of unreasonable risk, which urges the agency to consider a metric of a chemicals’ risk called a “margin of exposure.”

Margins of exposure compare exposure levels that found no health effects in test animal studies to human exposure. The larger the margin of exposure, the smaller the potential health risk.

California’s Environmental Protection Agency and a coalition of academic researchers joined by the American Congress of Obstetricians & Gynecologists, National Medical Association, and Physicians for Social Responsibility objected to the EPA’s use of a margin of exposure approach to assess risks.

That approach suggests “there is a ‘safe’ level of exposure below which no harm will occur,” the coalition wrote.

That may be true for a few chemicals, but cannot be an across-the-board assumption, the coalition wrote.

States, Water Agencies

In the Environmental Defense Fund’s comments and an interview with Bloomberg BNA, Denison and McPartland echoed those concerns about the margin of exposure method and pointed to several other examples of proposed definitions that they said would limit scientific advances.

The chemistry council’s proposed science definitions are its attempt to “put its thumb on the scale” and lock in use of specific risk analysis methods and assumptions, Denison said.

CalEPA, Washington state’s Department of Ecology and the National Association of Clean Water Agencies urged the EPA to use guidance—not regulations—to define science and risk terminology.

“Codification of specific terms will inhibit agency flexibility and responsiveness to evolving and changing science,” CalEPA wrote.

Andrew Rogers, director of legislative programs for the American Association for Justice, whose member attorneys represent individuals who argue that chemical exposures have harmed them, told Bloomberg BNA that Congress considered multiple definitions of the scientific terms during the years-long effort to overhaul TSCA and intentionally chose not to define them.

Requiring repeatable scientific experiments or “independently verified” results, as some of industry’s definitions would do, could prevent the use of epidemiological research on chemical exposures, according to Rodgers. “It could ignore what’s happening in the real world,” he said.

Let Science Advisers Weigh In

The Natural Resources Defense Council’s Rosenberg said Congress didn’t define the science terms nor did it direct the EPA to do so.

The TSCA amendments required the EPA to establish a Science Advisory Committee on Chemicals, which it has done, he said.

That committee should be consulted about the scientific approaches the EPA will use as it implements the TSCA amendments, Rosenberg said.

To contact the reporter on this story: Pat Rizzuto in Washington at

To contact the editor responsible for this story: Larry Pearl at

For More Information

The EPA's proposed chemical risk evaluation rule and comments can be found in Docket ID No. EPA-HQ-OPPT-2016-0654, available at

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