Ethylene oxide blood levels should be considered normal
A researcher from the University of Illinois-Chicago recently issued a brief summary of preliminary testing results concerning ethylene oxide levels in the blood of Illinois residents living in Lake County within a few miles of a medical instrument sterilization facility. Although the test results showed blood ethylene oxide levels squarely within the normal range, the release of information implied - with no supporting scientific data whatsoever - that the sterilization facility was responsible for "elevated" levels.
This facility, operated by Medline Industries Inc., uses ethylene oxide to sterilize critical medical devices and instruments needed every day in hospitals and other healthcare settings. The ethylene oxide process is the industry standard to protect patients from infections and the only available process for sterilizing countless products.
When those preliminary results were reported, understandable community concern resulted because the author asserted that residents nearer the Medline facility have higher levels of blood ethylene oxide than more distant residents. The implication was that the higher blood levels are associated with greater health risk.
In my 40-year career in toxicology - including as a consultant to the medical device industry - I know that a primary source of blood ethylene oxide is the human body itself because ethylene oxide is a normal product of metabolism. The two data points the researcher responsible for the study, Susan Buchanan, reported are completely within the normal range, but she does not mention this fact, and virtually none of the subsequent news reporting has mentioned it.
Twenty peer-reviewed scientific publications document average (nonsmoking) ethylene oxide-blood-hemoglobin levels ranging from 13-117 pmole/gmHb. The two results reported by Buchanan are 29.8 and 50.1 pmole/gmHb for residents more distant from and closer to the facility, respectively, both falling squarely within the normal range. Buchanan asserts that her results show a "statistically significant" difference between the two groups of residents, but it is impossible to verify that assertion because - inconsistent with scientific norms - she has provided none of the data or other information needed to do so. The groups were not randomly selected, biasing the results. Many other basic questions reflect the scientific unreliability of the data and undermine the conclusions drawn.
The one thing we can be sure of is that Buchanan's report shows that the ethylene oxide levels in people, whether living close to or distant from Medline's facility, are within the normal range. Local monitoring shows that ethylene oxide levels in the air, whether close to or distant from this facility, are within the normal range. There are many sources of human exposure to ethylene oxide, including the human body itself. Human bodies evolved making ethylene oxide. At normal levels of exposure, we are safe.
Gail Charnley, Ph.D., is a toxicologist in Washington, D.C., specializing in environmental health risk assessment and policy who studies the relationship between environmental exposures and public health outcomes. She is an independent researcher studying EtO sterilization for the broader sterilization industry, including Medline.