Texas ignores dangers of ethylene oxide in flawed report

In 2016, after careful analysis, and extensive internal and external peer review, and public comment, the U.S. Environmental Protection Agency (EPA) concluded that inhalation of ethylene oxide is “carcinogenic to humans.” Despite no new evidence that would alter EPA’s findings, the Texas Commission on Environmental Quality (TCEQ) just finalized a dangerously flawed report claiming that the cancer risk of ethylene oxide is far below EPA’s risk estimate.

As a scientist who worked at the EPA on its cancer assessment, and as a contributor to UCSF PRHE’s comments on the TCEQ’s 2019 draft assessment, I was dismayed to see TCEQ’s final report because it could jeopardize the health of exposed workers and those living near Texas’ high number of ethylene oxide emitting facilities, mostly low-income communities of color who face disproportionate exposures. Thus, on behalf of PRHE, I investigated what happened since the public comment period and the problems with the final report.

After the public comment period, the only revision TCEQ made was a quantitatively minor correction about the procedure used to adjust for potential increased early-life susceptibility. TCEQ submitted a revised report for a limited letter peer review by six reviewers but then made no further corrections to its cancer risk estimate. Most other public comments and UCSF’s comments exposing grave flaws in TCEQ’s assessment still apply. The final TCEQ report:

  1. discounts the breast cancer risks,
  2. uses a model for lymphoid cancer that does not reflect the data,
  3. uses a number of non-standard and non-health-protective procedures in the calculation of the risk estimate for lymphoid cancer from that model, and
  4. uses an erroneous “reality check” to support the use of that model.

A review of the peer review comments revealed that some of the six reviewers also had critical concerns with the TCEQ report, including on the major issues of breast cancer and the modeling of the lymphoid cancer data.

An evaluation of the breast cancer evidence relies heavily on an assessment of epidemiological data. There were two epidemiologists in the review group, and they appeared to be split over the conclusion. Two other reviewers were satisfied with TCEQ’s determination that regulatory decisions be based solely on the lymphoid cancer risks but indicated that it was important the cancer risk estimate be protective of breast cancer.  However, by discounting breast cancer, TCEQ is drastically underestimating the potential risks to women (see Table).

Fig 1
Table: Comparison of TCEQ and EPA unit risk estimates for ethylene oxide. TCEQ’s estimate for total cancer is far below EPA’s and is not protective of breast cancer risk to women. Source: Data in this graph were derived from EPA’s 2016 and  TCEQ’s 2020 assessments.

On the issue of model selection for the lymphoid cancer data, TCEQ rejected EPA’s model and instead used a model that does not provide a good representation of the data (see Figure).  Three of the four peer reviewers commenting on the modeling issues recognized that TCEQ’s rationales for this were unconvincing.

Fig 2
Figure: EPA and TCEQ models compared to categorical data (quartiles) from the NIOSH study of workers exposed to ethylene oxide. Source: extracted from EPA’s 2016 assessment, Figure 4-3.

Thus, despite the existence of EPA’s rigorous carcinogenicity assessment, which was extensively reviewed by a panel of 14 independent experts, and the absence of new data that would substantively alter EPA’s conclusions, and in contradiction to many public comments and some of its own peer reviewer comments—TCEQ has released a seriously flawed final report on ethylene oxide carcinogenicity which does not protect public health.

About the author

Jennifer Jinot is a former U. S. EPA staff scientist. Jennifer has over 25 years of experience in environmental health risk assessment, and she contributed to EPA’s 2016 cancer assessment of ethylene oxide, as well as EPA’s health assessments of secondhand smoke and trichloroethylene (TCE), among others. Jennifer has a multi-disciplinary background, including risk assessment work in toxicology, epidemiology, and the derivation of quantitative risk estimates, with a specialization in risk estimates based on human data.