Emerging Chemical Issues – Ethylene Oxide (Part 1 of 5): Why It Matters



In the past two years, hundreds of lawsuits have been filed against companies based on their emissions of a chemical called ethylene oxide (often referred to as “EtO” or “EO”). Multiple facilities that handle EtO also have been shut down on a temporary or permanent basis, and many others have been subjected to administrative enforcement actions or been required to amend permits and install millions of dollars of additional emission control equipment even when the companies were already in compliance with federal emission standards for EtO. Many of these actions have been predicated on the perceived health risks associated with EtO based upon a risk assessment performed by the U.S. Environmental Protection Agency in 2016 that has been heavily criticized in the scientific community.

Over the coming days, we will cover recent regulatory developments and emerging industry and regulatory challenges. But first, some background is in order; namely: what is EtO, why the sudden interest from regulators and plaintiffs, and is this relevant to your business.

What Is EtO

Ethylene oxide (EtO) is a volatile gas that has been regulated as a hazardous air pollutant (HAP) under the Clean Air Act (CAA) since 1990.

There are two main industrial sources EtO:

  1. In the chemical manufacturing industry, which uses EtO as an intermediate in the production of other derivative chemicals (e.g., ethylene glycol), which according to the American Chemistry Counsel (ACC) are then used in the manufacture of a wide array of products, including fabrics and polyester fibers for clothes, upholstery, carpet and pillows, automobile antifreeze, household and industrial cleaners, cosmetics, shampoos, fiberglass, polyethylene terephthalate plastic resin (used in beverage containers and packaging film), polyurethanes, and plasticizers.
  2. Sterilization and fumigation operations, which use EtO as a disinfectant, primarily for medical devices, and food products (like spices). In fact, according to the Food and Drug Administration (FDA), almost half of all sterile medical products are sterilized with EtO, and for many medical devices, FDA has determined that sterilization with EtO may be the only method that effectively sterilizes and does not damage the device during the sterilization process, as opposed to other sterilization methods like radiation and steam.

Of these two primary industrial uses, chemical manufacturing is by far the primary driver of industrial EtO emissions, with industry sources claiming that medical device sterilization accounts for less than 1% of industrial EtO emissions.

These industrial emission sources of EtO are already regulated by the Environmental Protection Agency (EPA) under the CAA, which requires EPA to issue a National Emission Standards for Hazardous Air Pollutants (NESHAP) for each category of sources that emit HAPs (including EtO). EPA has issued NESHAPs that limit EtO emissions from a variety of sources, including, most notably, various types of chemical manufacturers (including NESHAPs F, G, U, PPP and FFFF), commercial sterilization and fumigation operations (both covered by NESHAP O), and area source hospital sterilizers (covered by NESHAP WWWWW). After a NESHAP has been set for a category of sources, the CAA requires EPA to conduct a Residual Risk and Technology Review (RTR) within eight years to reassess the health risks remaining after implementation of the NESHAP, and any technological advancements that may make it possible to achieve further emission reductions. Every subsequent eight years, EPA must again review and revise the standards, if necessary, to account for improvements in air pollution controls and/or prevention. Occupational employee exposures to EtO are separately restricted and regulated by the Occupational Safety and Health Administration (OSHA).

There are also several nonindustrial sources of EtO that are not directly regulated under the CAA. For instance, EtO can likely be emitted from various consumer activities when consumers use commercial products that have EtO in them. Also, according to the most current draft of the CDC/Agency for Toxic Substances and Disease Registry (ATSDR)’s toxicology profile for EtO, other known sources of EtO include (1) the combustion of hydrocarbon fuels (including oil, natural gas and gasoline combusted in vehicles, airplanes, generators and industrial boilers), such that “significant amounts” of EtO are likely emitted due to vehicle exhaust; (2) tobacco smoke (both direct use and second-hand environmental smoke); and (3) natural degradation of ethylene into ethylene oxide through the metabolisms of certain plants and microorganisms, though the total significance of this naturally produced EtO has not yet been established.

The 2016 IRIS Study

The recent litigation and regulatory actions related to EtO are ultimately grounded in a study published in December 2016 by EPA’s Integrated Risk Information System program (IRIS). This study determined that the Unit Risk of Exposure for EtO (IRIS EtO URE) was significantly lower than had been found by prior studies, i.e., that EtO was associated with carcinogenic risk even at much lower exposure levels than previous studies had found (assuming a lifetime of continuous exposure). The IRIS EtO URE also changed EtO’s classification from “probably carcinogenic to humans” to “carcinogenic to humans.” At the time, EPA’s independent Science Advisory Board (SAB) raised several questions about the basis for the 2016 study, including the fact that the study did not take into account background levels of EtO when setting a risk threshold for EtO exposures. But EPA published the report in the final month of the Obama administration, without resolving all comments from the SAB. Because this new risk value for EtO was not set as part of a public rulemaking, it was not subject to public notice and comment, and thus could not be challenged until EPA used it to actually set an enforceable emission standard.

To give some perspective on how small the IRIS EtO URE is, subsequent studies have found that it is more than two orders of magnitude below the amount of EtO that EPA has subsequently measured to be in ambient air not associated with industrial emission sources. In fact, recent studies suggest that industrial sources only account for a small percentage of the average individual’s EtO exposures, with over 94 percent of EtO exposures happening as a result of metabolic processes, such that the IRIS EtO URE is more than three orders of magnitude below the equivalent concentrations of metabolically produced ETO in the nonsmoking population.

Because the 2016 IRIS EtO URE was a study only and did not actually affect the regulations applicable to industry, it went relatively unnoticed until more recent events brought it to the forefront of toxic tort litigation and environmental compliance practice.

The 2014 NATA, and Why People Care

The 2016 IRIS EtO URE only began to practically affect events in 2018, when EPA used it to evaluate nationwide cancer risks as part of the 2014 National Air Toxics Assessment (NATA) (the 2014 NATA was published in August 2018, but is based on emissions and air quality data from 2014). The NATA evaluates various health risks, including cancer, in census tracts across the United States based on emissions of 180 different HAPs. In EPA’s own words, the “NATA is a screening tool, used to help EPA and state, local and tribal air agencies find out if areas, pollutants or types of pollution sources need to be looked at further to better understand risks to public health. NATA provides broad estimates of the risk of developing cancer and serious noncancer health effects over census tracts across the country.” Using the 2016 IRIS EtO URE as a screening risk value for cancer for the first time, the 2014 NATA identified a number of census tracts where risk should be further studied (but specifically disclaimed that the NATA was itself an analysis of actual cancer risks).

Because the risk factor used to assess EtO cancer risk had significantly changed since the last time EPA had issued a NATA (in 2015; the 2011 NATA), the 2014 NATA suddenly purported to find a potential for increased cancer risk in many census tracts where industrial EtO sources were located. This predictably caused an uproar among local community action groups in those identified geographic tracts, which interpreted the preliminary screening from the NATA as an indication that they were at high risk of cancer. After all, if the IRIS EtO URE is a good predictor of cancer risk, and if the NATA was based on sound emissions data, then the census tracts flagged by the 2014 NATA might be expected to have elevated cancer risks of an additional 1 cancer per 10,000 continuous (24/7) lifetime exposures (70 years). The flames were fanned by plaintiffs’ attorneys, who immediately began trawling for potential plaintiffs in areas that the 2014 NATA highlighted and have since brought several hundred lawsuits against industrial EtO sources across the nation. Accordingly, since publication of the 2014 NATA, an industrial user of EtO can no longer expect that it is safe from suit simply because it complies with all laws and regulations.

Stay tuned for updates and analysis related to recent regulatory developments, important litigation, and unique challenges faced by regulators and industry when dealing with EtO issues.

DISCLAIMER: Because of the generality of this update, the information provided herein may not be applicable in all situations and should not be acted upon without specific legal advice based on particular situations.

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