Scientists Critique EPA’s Draft Evaluation of Phthalate DCHP

A collection of scientists, academics, and clinicians have called for “extensive revisions” to EPA’s draft risk evaluation for dicyclohexyl phthalate (DCHP), arguing that the assessment “failed to incorporate the best available science and makes a number of scientifically unsupported assumptions.”

The May 9 comments were submitted by the Program on Reproductive Health and the Environment at the University of California San Francisco.  The commenters raise a number of methodological concerns with EPA’s December 2024 draft, which preliminarily determined that nine of 24 evaluated conditions of use for DCHP raised concerns, all involving occupational exposures.

A central criticism is EPA’s reliance on central tendency estimates, rather than high-end exposure scenarios, for many conditions of use. This approach, the commenters argue, “sets a dangerous precedent that risks to more highly exposed individuals can be dismissed or downplayed without scientific support.”

The commenters also object to EPA’s blanket exclusion of human epidemiology studies from its dose-response assessment, justified by uncertainties over exposures and testing methods.  That rationale “demonstrates a bias against environmental epidemiology, rather than a thoughtful approach to evidence evaluation that is consistent with best practices in systematic review,” according to the comments.

The group additionally claims that EPA failed to conduct an up-to-date literature search, omitting certain studies conducted since 2019.  As a result, they argue that the draft overlooks newer evidence linking DCHP to liver toxicity.

Alongside the Toxic Substances Control Act (TSCA) risk evaluation, DCHP is also part of EPA’s first-ever cumulative risk assessment for a group of five phthalates. A blog post on that effort, published prior to the January 2025 draft, can be found here.