If you have an ACS member number, please enter it here so we can link this account to your membership. (optional)

ACS values your privacy. By submitting your information, you are gaining access to C&EN and subscribing to our weekly newsletter. We use the information you provide to make your reading experience better, and we will never sell your data to third party members.



EPA affirms ethylene oxide’s health hazards

Agency rejects industry-backed assessment from Texas agency that gas is less toxic

by Cheryl Hogue
December 30, 2022


The US Environmental Protection Agency has roundly rejected a controversial, chemical industry-backed analysis of the health hazards of ethylene oxide.

In a Dec. 21 notice, the EPA says it is standing firm on an assessment of the carcinogenic gas that the agency finalized in 2016 after extensive scientific peer review and public comment. The agency concludes there is no new scientific evidence that would alter key aspects of that hazard assessment, despite industry opposition and an alternative assessment by a Texas regulatory agency.

Top emitters
US facilities with largest amounts of ethylene oxide releases to air in 2021.
Table lists the top ethylene oxide emitters iin the US in 2021.
Source: US EPA Toxics Release Inventory.

The EPA adds that it will maintain a 2020 Clean Air Act regulation for chemical manufacturers that relies on its assessment. The regulation requires companies to curb ethylene oxide emissions from leaks, vents, and storage tanks to protect the health of people living near industrial plants.

Ethylene oxide is a chemical building block made from natural gas or petroleum. It is used to produce surfactants and plastics and to sterilize medical equipment.

In 2020, the Texas Commission on Environmental Quality (TCEQ) challenged the EPA’s conclusions in its own assessment of the chemical. The TCEQ determined that ethylene oxide is far less hazardous—a less potent carcinogen—than the EPA had concluded.

The US chemical industry’s main advocacy group, the American Chemistry Council (ACC), along with the TCEQ and Huntsman Petrochemical urged the EPA to reconsider its rule and to adopt the TCEQ’s conclusions. Until recently, Huntsman operated a plant in Port Neches, Texas, that has had the nation’s highest or second-highest annual ethylene oxide emissions since at least 2017, according to Toxic Release Inventory data that the company reported to the EPA. Huntsman completed the sale of the plant to Indorama Ventures in 2020.

In response to the requests, the EPA agreed in 2021 to take another look at its assessment. That effort culminated in the Dec. 21 notice reaffirming the agency’s earlier work.

The EPA notice calls the TCEQ determination “not scientifically sound” because it excludes scientific evidence suggesting that ethylene oxide causes breast cancer in women. The agency notes that the ACC supports this exclusion.

The EPA determined that available epidemiological evidence that exposure to ethylene oxide can cause breast cancer in women is strong, so the agency included this data in its assessment. It notes that its Science Advisory Board, a panel of experts from outside the agency, supported this decision.

The ACC says in an emailed statement that it is studying the EPA notice. “We remain concerned that EPA has either not yet responded or has responded inadequately to the core, scientific and substantive issues ACC and TCEQ have raised,” it adds.

In a related development, environmental advocates are calling on the EPA to strengthen the 2020 rule by requiring ethylene oxide emission limits to apply at all times, and not allow exemptions for plant malfunctions that cause releases to spike. They are also urging the agency to require facilities to monitor ethylene oxide emissions at their fencelines to protect neighboring communities.


This article has been sent to the following recipient:

Chemistry matters. Join us to get the news you need.