• TSCA requires that for each risk evaluation completed on a High-Priority Substance, EPA must begin a new risk evaluation.
• The scope of a risk evaluation will include the hazards, exposures, conditions of use, and the potentially exposed or susceptible subpopulations the EPA expects to consider.
• A draft scope will be published in the Federal Register.

The risk evaluation process is the second step, following Prioritization and before Risk Management, in the Environmental Protection Agency’s (EPA’s) existing chemical process under the Toxic Substances Control Act (TSCA). The purpose of risk evaluation is to determine whether a chemical substance presents an unreasonable risk to health or the environment, under the conditions of use, including an unreasonable risk to a relevant potentially exposed or susceptible subpopulation.

As part of this process, EPA must evaluate both hazard and exposure, exclude consideration of costs or other non-risk factors, use scientific information and approaches in a manner that is consistent with the requirements in TSCA for the best available science, and ensure decisions are based on the weight-of-scientific-evidence. Here is an overview of the steps in EPA’s risk evaluation process for existing chemicals:

A. Initiation of the risk evaluation

A risk evaluation can be initiated by EPA based on the outcome of Prioritization or initiated by EPA based on acceptance of a manufacturer’s request for a risk evaluation:

• EPA-Initiated risk evaluations
  • With the passage of the Frank R. Lautenberg Chemical Safety for the 21st Century Act (LCSA) in 2016, EPA was required to select the first 10 chemicals to undergo risk evaluations from the 2014 Update to the TSCA Work Plan. Following the first 10 chemicals, EPA has been conducting risk evaluations on chemical substances designated as High-Priority Substances through the Prioritization process.
  • TSCA requires that for each risk evaluation completed on a High-Priority Substance, EPA must begin a new risk evaluation. By the end of calendar year 2019, EPA must have had at least 20 chemical risk evaluations ongoing at any given time on High-Priority Substances. The law requires that at least half of all EPA-initiated risk evaluations be drawn from the 2014 Update to the TSCA Work Plan, until that list has been exhausted.
• Manufacturer-requested risk evaluations
  • Chemicals may be evaluated following EPA’s approval of a manufacturer’s request for a risk evaluation of a chemical they manufacture. The number of chemicals undergoing risk evaluation as the result of such requests must constitute 25 to 50 percent of the number of EPA-initiated risk evaluations, if EPA receives a sufficient number of compliant requests.

B. Components of a risk evaluation

1. Scope of the risk evaluation

• The scope of a risk evaluation will include the hazards, exposures, conditions of use, and the potentially exposed or susceptible subpopulations EPA expects to consider. The scope will also include:
  • A Conceptual Model, which will describe the relationships between the chemical, under the conditions of use, and humans and the environment.
  • An Analysis Plan, which will identify the approaches and methods EPA intends to use to assess exposures and hazards.
• Conditions of use under TSCA means “the circumstances, as determined by the [EPA] Administrator, under which a chemical substance is intended, known, or reasonably foreseen to be manufactured, processed, distributed in commerce, used or disposed of.” For purposes of prioritization, the EPA Administrator may determine that certain uses fall outside the definition of conditions of use. During the risk evaluation scoping process, EPA may decide to narrow the scope of the risk evaluation further, potentially excluding conditions of use that present low risk.
• Draft scope
  • A draft scope will be published in the Federal Register no later than three months from the initiation of the risk evaluation process.
• 45-day public comment period on the draft scope
  • A docket will be opened for no less than 45 days to facilitate public comment on the draft scope.
• Final scope
  • A final scope will be published no later than six months after initiation of the risk evaluation, as required by the law.

2. Hazard assessment

• EPA will identify the adverse health or environmental effects caused by exposure to the chemical. Hazards may include, but are not limited to, toxicity with respect to cancer, mutation, reproductive, developmental, respiratory, immune, and cardiovascular impacts, and neurological impairments.

3. Exposure assessment

• EPA will identify, where relevant, the likely duration, intensity, frequency, and number of exposures to a chemical under the conditions of use. This assessment will also include the nature and types of individuals or populations that are exposed to the chemical.

4. Risk characterization

• EPA will integrate and assess the reasonably available information on hazard and exposure and will also include considerations of information quality and alternative interpretations.

5. Risk determination

• EPA will make a draft determination as to whether the chemical substance, under the conditions of use, presents an unreasonable risk to health or the environment. Those conditions of use determined to present an unreasonable risk to health or the environment will move immediately into risk management.

C. Publication of the risk evaluation

1. Draft risk evaluation

• Each draft risk evaluation will be peer reviewed.
• A draft scope will be published in the Federal Register.
• 60-day public comment period on the draft risk evaluation. A docket will be opened for no less than 60 days to facilitate public comment on the draft risk evaluation.

2. Final risk evaluation

• A final risk evaluation will be published no later than three to three-and-a-half years after identification of the chemical as a high priority for risk evaluation.