EPA Issues Final Revision to Cyclic Aliphatic Bromide Cluster (HBCD) Risk Determination

In late June 2022, the final revision to the risk determination for the cyclic aliphatic bromide cluster (HBCD) risk evaluation was made available by the U.S. Environmental Protection Agency (EPA). This aligns with and is part of the Agency’s ongoing efforts to help protect human health and the environment. In this blog post, we briefly review HBCD and consider both the risk evaluation and corresponding revision.

Cyclic Aliphatic Bromide Cluster

Cyclic aliphatic bromide cluster is a non-volatile solid comprised of three related chemicals:

  • hexabromocyclododecane
  • 1,2,5,6,9,10-hexabromocyclododecane
  • 1,2,5,6-tetrabromocyclooctane
Chemical NameCAS Registry Number

Source: U.S. Environmental Protection Agency

HBCD has seen use in a variety of industrial applications, including the manufacture of solder, automobile replacement parts, and more. Its principal use, however, has been as a flame retardant in polystyrene foam. While several routes of exposure to HBCD are possible, dermal and inhalation exposure tend to be the most common routes.

HBCD is persistent, bioaccumulative, and toxic (PBT). Given its classification as a persistent organic pollutant, it is (as of 2018) no longer produced in the United States. Many other countries have also banned HBCD use and manufacture.

Final Risk Evaluation and Revision to Risk Determination

The final risk evaluation for HBCD was initially released by the EPA in September 2020. This evaluation yielded several key findings, based on an assessment of 12 conditions of use.

  • Unreasonable risks to the environment were found (for six of the 12 conditions of use)
  • No unreasonable risks to the general population were found
  • No unreasonable risks to consumers were found
  • Unreasonable risks to workers and occupational non-users were found, particularly when dealing with materials in construction
  • (In this evaluation, risk to workers was considered both with and without the use of personal protective equipment (PPE))

With the revised risk determination, the EPA has concluded that under HBCD's use conditions, it presents unreasonable risks overall in consideration as a “whole substance”. For workers, there is also not an assumption that PPE is appropriately worn at all times. While six of the 12 conditions of use were found to yield unreasonable risks to the environment in the original 2020 risk evaluation, four of these six conditions now also present unreasonable risks relative to workers’ health. They include:

  • Manufacturing (Import)
  • Processing: Incorporation into articles
  • Processing: Incorporation into formulation, mixture, or reaction products
  • Processing: Recycling (e.g., of XPS and EPS foam, resin, panels containing HBCD)

More detailed information on changes associated with the final revision to the risk determination for the HBCD risk evaluation may be found by reviewing Federal Register citation 87 FR 38747.

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