It’s time to regulate chemicals as classes

~ PRHE

A couple of years ago I went to a wool and sheep festival where, for the first time, I watched dogs herd sheep. They were so smart and efficient, one dog handled dozens of sheep! Regulatory agencies should take a similar approach: chemicals, as sheep, should be assessed and their risk managed by groups.

There are hundreds of thousands of chemicals in commerce. Historically, however, regulatory agencies assess and manage their risk one at the time. This approach is like assigning one dog per sheep. It takes a lot of resources and is not very efficient or effective.

Add to this the growing demand for new chemicals and new uses of chemicals, which makes the current chemical-by-chemical risk assessment approach unsustainable.

So, what do we do? Group them! 

Assessing and managing the risk of chemicals based on groups or families makes more sense and has many advantages, chief among them reducing exposure to many harmful chemicals at once which can improve public health. Grouping chemicals will also allow agencies to consider the cumulative impact of exposure to chemicals and their related chemical family members, which will improve the risk estimation leading to better protection. Grouping chemicals will also increase efficiency, reduce costs, and enable policymakers to make decisions more quickly.

Unfortunately, grouping chemicals into categories or families is uncommon in the United States. For instance, unless there is a legal requirement, regulatory agencies like EPA are likely to continue using familiar and customary approaches; lack of experience and best practices and procedures in implementing a group approach are some of the barriers holding back regulators.

As part of our new paper, Advancing the science on chemical classes, we identified that similar chemical structure is the most common grouping approach for risk assessment by regulatory agencies and non-regulatory science-based organizations domestic and internationally. Other common approaches were based on toxicity to the same organ (e.g., liver) or the same biological function (e.g., mimicking estrogen hormone) regardless of whether the chemical structure is similar.

Critics of the classes or grouping approach are concerned that “good chemicals” will be lumped with the “bad chemicals” just because they look alike, resulting in excessive regulations. They’re also worried that the groups will be so large, rendering them useless. However, both of these are simplistic interpretations.

We propose using a decision tree (Figure 1, below) to assign any chemical to a group. The framework is grounded in two equally important components: the decision context in which the group will be used (e.g., regulation requiring the use of categories; chemical prioritization for assessment or replacement) and the science-based considerations supporting the rationale for the established group boundaries. Stakeholders that disagree with the outcome would be able to present evidence demonstrating why either certain chemicals don’t belong to the group or should be added.

This will result in smaller and larger groups.

Figure 1. [Click to enlarge]

Our recommendations

The decision tree would help decisionmakers develop the best possible classes to achieve health-protective regulatory outcomes and avoid regrettable substitutes. We believe that our approach provides elements to advance the use of chemical grouping because it: 

  • Eliminates the perceived barrier of lacking a single universal method with multiple variations in approaches to establish and manage chemical families.
  • Provides flexibility to select already available grouping methods or develop new ones to, among others, implement existing laws, renew public health protections and incorporate scientific advances to ensure equitable outcomes.
  • Stimulates coordination and collaboration across agencies regulating the same chemicals because it incorporates questions about existing grouping methods within and outside an agency. 

Using a flexible decision-tree approach is an opportunity to systematically incorporate chemical classes into the decision process and better protect the public’s health.

There are ongoing successful cases of chemical grouping approaches and multiple available methods that may meet the user’s needs including assessing chemical safety, disclosure when chemicals are released to the environment, selection of biomonitoring chemicals, and manufacturing and product stewardship. There are statutes and regulations that allow the use of grouping, and more importantly, we have found neither an explicit exclusion of using the class approach nor a legal requirement to conduct chemical-by-chemical risk assessments.

EPA, like other regulatory agencies, has mounting responsibilities. The authors of our paper strongly believe that regulators should explore and use the option of grouping chemicals in classes whenever possible for hazard or risk assessment and regulatory or policy activities. This approach would potentially alleviate the resource constraints faced by the agencies and would ensure that the regulators keep up with both the science and decisions made by sister agencies.

This post is fifth and final in a series about our Roadmap papers, which provide scientific recommendations to update chemical risk assessment to better reflect exposures and hazards, guide decision-making, and protect the public’s health. Lead authors of the papers will discuss their recommendations on a webinar on Thursday, February 2nd. Register here: bit.ly/san-jan23

Other blogs in this series:

About the Author

Maricel V. Maffini, PhD is an Independent Consultant based in Maryland. For the last decade, she’s worked on food chemical safety policy and regulation. Previously, she conducted research on cancer and endocrine disruption.

Published by PRHE

PRHE’s mission is to create a healthier environment for human reproduction and development through advancing scientific inquiry, clinical care and health policies that prevent exposures to harmful chemicals in our environment.