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KEEPIN’ IT CLEAN

June 7, 2022

 

At one or more times in our life we are all likely to end up in a doctor’s office or hospital for a medical procedure. Or we may decide to give blood so that someone else’s life can be improved, or even saved. Often medical staff will use equipment to monitor our symptoms or to take measurements. Sometimes this equipment is used only once, like gloves, but often it is reused, such as stethoscopes or scalpels.

So how does the medical community keep this equipment free of contaminating bacteria, viruses and fungi? Through sterilization! All of the various medical tools or equipment used in doctors’ offices or hospitals are routinely sterilized, either by wiping down surfaces with disinfectants, reusing medical tools after heating to a level that kills such organisms, or using equipment only once. All of these processes work and are an important part of keeping us safe. However, even the one-use equipment must be sterilized beforehand. So how does this get done?

Several ways exist to sterilize one-use medical equipment, such as using radiation, or heat, or a disinfecting chemical such as ethylene oxide. Each of these ways has advantages and disadvantages. For example, the plastic tubes that are used to administer blood and saline to many of us cannot be sterilized by heat or radiation, since this would generally melt the plastic. In such cases ethylene oxide is used since is it dry, penetrates the openings in the plastic, and leaves little to no residue. In other words, ethylene oxide and similar disinfectants are invaluable tools in keeping people safe and free of infections from potentially unsanitary medical equipment,

As you might imagine, the use of disinfection also comes with a risk (just as not using disinfection comes with a risk!) In the case of ethylene oxide, the risk is the development of cancer but only at very high exposures, well beyond what you might get from hospital equipment. As I have stated before, government agencies work very hard to develop safe levels for chemicals like ethylene oxide, that is, levels that will cause little, if any cancer, but that would still allow the use for medical sterilization. Not surprisingly, the U.S. Environmental Protection Agency (EPA) developed a safe level of ethylene oxide in 2016 that I reviewed for them. However, many folks are now re-reviewing this EPA value because new information shows that our bodies actually make a small amount of ethylene oxide every day, just from normal metabolism. Ripening fruit also emits the gas ethylene, a small amount which our bodies covert to ethylene oxide. Fortunately, these amounts are well below any level shown to cause cancer.

This new knowledge suggests that EPA’s older level was overly safe (not a bad thing), but using it now suggests us getting more cases of a specific kind of cancer than actually found in our population. A more recent government assessment by the Texas Commission for Environmental Quality analyzed this new knowledge and proposed a much higher safe level than EPA. Texas’ value is still safe and also consistent with what our bodies make every day. Other groups, such as the U.S. Food and Drug Administration, have also reviewed this new knowledge and came to roughly the same conclusions as Texas.

Because of these different estimates of safe levels and the intense need for medical sterilization during the COVID pandemic, ethylene oxide has been in the news. Its use in medical device sterilization facilities has often been misunderstood as a threat to public health because of the cancer finding at very high exposures. In part, this misunderstanding is…understandable, especially in light of the EPA’s older assessment that we now know did not fully account for our bodies’ own production of ethylene oxide or its prevalence in the environment from many other sources. 

So will EPA use this additional information and modify its safe level? Perhaps. EPA could easily say that their older assessment was the best they could do at the time (I reviewed it for them so this is true), say correctly that new data have since been published, and then state that Texas has done a good job of standing on its shoulders and going the next step to a more scientifically accurate, but still safe level of EtO exposure.

But if EPA does not, this we do know: ethylene oxide does an excellent job in cleaning medical equipment; our bodies make it daily at levels that are well above EPA’s older safe level; and we are exposed to natural levels of it from sources other than the medical sterilization plants. Furthermore, the pandemic has shown us how important the need is for sterilized medical equipment. Nor is it reasonable to label human breath as hazardous as a Superfund waste site, which is the practical implication of continuing to use EPA’s older safe level.

Michael L. Dourson, Ph.D., DABT, FATS, FSRA
President and Director of Science

WEEL OEL

Occupational Exposure Limits (OELs) are designed to safeguard the health of healthy workers during their careers. These limits are based on the assumption of repeated daily exposure throughout a working lifetime, typically averaged over an 8-hour workday. Their purpose is to prevent both immediate (acute) and long-term (chronic) health issues arising from workplace exposures. It’s important to note that OELs are not intended for the general public, which includes vulnerable groups like infants, the elderly, and those with pre-existing health conditions.

Workplace Environmental Exposure Levels (WEELs) are health-based guidelines for chemical hazards in the workplace. These values represent air concentrations believed to protect the majority of workers from negative health effects resulting from occupational chemical exposure.

The WEEL Process
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The development of new or revision of existing WEELs is typically assigned to voluntarily designated subcommittees. A subcommittee usually comprises 3 – 4 members from the WEEL Committee. New WEELs are developed using the OARS-WEEL administrative standard operating procedure (SOP), while existing WEELs are usually revised every 10 years, unless the availability of significant new data which may impact the existing WEEL value compels the committee to make a revision sooner. The OARS-WEEL SOP contains procedures and guidelines governing conflicts of interest, draft document preparation, literature searches, draft document review, balloting process, post-ballot WEEL documentation quality assurance scientific review, and publication.

Once a subcommittee has prepared a draft WEEL document, a review of the draft is scheduled for the next available Committee meeting. The WEEL Committee members are expected to have reviewed all such drafts prior to the meeting. If no major changes are necessary to a draft, the attending Committee membership may, by a simple majority, approve the WEEL for balloting. Alternatively, the Committee may direct the subcommittee to revise the WEEL and present it for further discussion at a future meeting. If a ballot is not approved by a two-thirds majority of non-abstaining Committee members, it is discussed at the next Committee meeting to determine the appropriate course of action. Once the WEEL is approved by a two-thirds majority of non-abstaining Committee members, copies of ballot comments are forwarded to the designated subcommittee and all substantive comments must be addressed in the final draft. If resolution of a substantive comment results in a change to the WEEL value or a change in the basis for the value, the draft must be re-balloted.

Once all comments have been addressed on a successfully balloted draft, document formatting and editorial review are performed by TERA, before the draft WEEL document is made available for public comment (usually for a period of 30 days but may be extended if the need arises). After the public comment period has elapsed, comments are addressed by the subcommittee responsible for that specific draft, after which the WEEL documentation is submitted to Toxicology and Industrial Health (TIH), a peer-reviewed medical journal that covers research in the fields of occupational health and toxicology, for publication. A thorough review of the galley proof by the scientific content quality coordinator at TERA, and proofreaders and editors at TIH is the penultimate step before eventual publication of the WEEL documentation.

The WEEL Committee

The OARS-WEEL Committee is composed of volunteer experts specializing in the scientific determination of occupational exposure levels. This committee actively seeks a balanced representation of professionals from toxicology and industrial hygiene, drawing upon a diverse range of experience from industry, government, academia, and consulting. Importantly, each member contributes to the Committee based on their individual expertise and not as an official representative of their respective employer, organization, or agency.