The Texas Commission on Environmental Quality (TCEQ) released a report on the carcinogenic potential of ethylene oxide (EtO) in humans earlier this year, challenging previous conclusions by finding no increased risk of cancer from exposure to EtO.
EtO has been safely used for a century and has been studied and monitored regularly since the 1920s. It is a chemical with many industrial applications, including use in the sterilization of personal protective equipment (PPE) and other medical equipment. Up to 20 billion medical devices each year utilize EtO worldwide, and approximately 50% of medical supplies in the United States are sterilized by ethylene oxide annually, giving EtO a crucial role in keeping medical facilities and personnel safe during the Covid-19 pandemic by ensuring that front line workers are protected from further spread of the virus.
A 2016 study conducted by the United States Environmental Protection Agency (USEPA) concluded that EtO increases the risk of certain types of cancers in humans exposed to high doses of the chemical.
However, the TCEQ study issued a strong rebuttal to those findings, stating that, “Concerns about the carcinogenic risk posed by EtO do not stem from EtO’s carcinogenic potency, but rather USEPA’s scientifically-flawed assessment of it.” Additionally, they could not simply “get on board” with the EPA study results after conducting their own study, because the state agency used new data that had become available after 2016 and expressed concerns about the “dire consequences” that could result from a ban on the use of EtO.
The major difference between the two studies is that TCEQ chose a standard dose-response model (Cox proportional hazards model) supported by the mode of action by which EtO may cause cancer as well as other important considerations, while USEPA chose an unconventional, overall supra-linear model for which they acknowledge there is no mode of action support.
Both studies used the same sample population of 17,000 people. However, the TCEQ contends that it has demonstrated its dose-response assessment to accurately predict the actual number of lymphoid cancers that occurred in the key study population, while USEPA’s model is demonstrated to be statistically significantly over-predictive of the cancers that occurred in that population.
Both TCEQ and USEPA agree that EtO has not been conclusively demonstrated to cause cancer in people. In workers exposed to concentrations millions of times higher than the general public, some studies show an association with increased cancer risk while others do not. And, while some animals exposed to even higher EtO concentrations developed certain cancers, these data are of highly questionable relevance to humans.
Moreover, the TCEQ states that its dose-response assessment considers new data and analyses—not just a different methodology: “The scientific weight of evidence clearly indicates that TCEQ’s assessment conducted using the standard Cox proportional hazards model results in more reliable and reasonable estimates of excess risk than USEPA’s unconventional, overall supra-linear two-piece spline model.”
The Impact
Set aside for a moment the impact that scientific studies may have on litigation that may result from exposure to EtO— litigation that could generate huge awards for tort attorneys while decimating EtO manufacturers and the thousands of workers that rely on those facilities to feed their families. The results of these studies impact the decisions that are being made by public policymakers today, and if those decisions are based on incomplete, inaccurate, or incorrect scientific studies, the “dire consequences” pointed out by TCEQ officials would be felt immediately.
The EPA study has triggered some policymakers to call for EtO sterilization facility closures. Without adequate availability of EtO sterilization, the FDA anticipates a national shortage of critical PPE supplies and medical devices.
Bottom line: The TCEQ study affirms the safe and well-regulated use of EtO, which is critical to our health care system and to the continued availability of safe, effective, and high-quality medical devices. Consequences from the closure of facilities will be difficult to reverse, and ultimately could result in years of spot or nationwide shortages of critical medical devices which could compromise patient care. Finally, the study also affirms the need for thorough ongoing research that utilizes appropriate methodologies and takes into account new data in order to produce the most accurate results the people can trust, and policymakers can use.