The End of “One-Size-Fits-All”: Understanding EO Residual Limits in ISO 10993-7:2026
The release of ISO 10993-7:2026 marks one of the most significant changes to ethylene oxide (EO) residual evaluation in decades. For years, manufacturers, laboratories, and regulatory teams operated within a relatively stable framework built around standardized exposure categories and broadly applicable allowable limits. That approach provided predictability, but it also relied heavily on generalized assumptions about patient exposure and device use.
The revised standard changes that model entirely.
Rather than relying on fixed category-based limits, ISO 10993-7:2026 introduces a toxicology-driven framework that requires allowable EO and ethylene chlorohydrin (ECH) limits to be derived based on how a device is actually used, who it is used on, and how long exposure occurs. The shift is substantial—not because the science of toxicology itself is new, but because the standard now expects those toxicological principles to be applied directly to device-specific exposure scenarios.
At the center of the revision is the concept of tolerable intake (TI), expressed in micrograms per kilogram per day (µg/kg/day). These TI values serve as the scientific foundation for evaluating exposure risk, but importantly, they are no longer used as direct acceptance criteria. Instead, manufacturers must now convert those toxicological thresholds into allowable limits that are specific to the device and intended clinical use. Compliance is ultimately determined using calculated allowable limits expressed in milligrams per device.
This marks the end of the “one-size-fits-all” paradigm that has historically characterized EO residual assessments.
Under the revised framework, allowable limits are no longer universally applied across broad exposure categories. Instead, they are determined case by case, taking into account factors such as patient population, duration of exposure, cumulative exposure over time, and the potential use of multiple devices simultaneously. In practical terms, two devices that may once have shared the same allowable EO residual limit could now require entirely different acceptance criteria depending on how they are clinically used.
For many manufacturers, one of the first questions is whether these changes dramatically alter existing limits. The answer depends heavily on the type of device and the exposure scenario involved.
For limited exposure devices intended for adult populations, the calculated allowable limits may not differ significantly from historical values. Many legacy assumptions already aligned reasonably well with adult body mass and short-duration exposure scenarios. As a result, organizations evaluating these products may find that the practical impact is relatively modest.
The more meaningful changes emerge with prolonged and long-term exposure devices. The revised framework explicitly incorporates cumulative exposure considerations, meaning allowable limits must now reflect repeated or continuous patient exposure over time. Duration is no longer simply a classification category—it directly affects how allowable limits are calculated.
This introduces a level of precision that more closely reflects real-world clinical exposure, but it also increases the complexity of risk assessments. Manufacturers must now clearly define intended use duration, anticipated frequency of exposure, and potential repeated use scenarios within their toxicological evaluations. These assumptions are no longer secondary considerations; they directly influence compliance outcomes.
The revised standard also places far greater emphasis on defining the intended patient population. Body mass now plays a central role in determining allowable exposure, which means generalized assumptions about an “average adult” may no longer be sufficient in many situations. Pediatric, neonatal, and infant populations require explicit consideration, particularly when products may reasonably be used across multiple patient groups.
As manufacturers begin interpreting the revised framework, some may choose to apply conservative body mass assumptions—such as infant body weight (~3.5 kg)—particularly when products could be used across multiple patient populations or when worst-case exposure assessments are desired.
While this may result in more restrictive allowable limits, it can help ensure that exposure assessments remain protective across a wide range of potential users and may support a more conservative regulatory position. This type of approach aligns with the broader risk-based philosophy reflected throughout the ISO 10993 series.
Navigating the Regulatory Transition Period
An additional challenge for manufacturers is the current regulatory transition period surrounding ISO 10993-7:2026 implementation.
While the revised standard has been published and is expected to influence global biocompatibility and sterilization strategies, formal FDA recognition and adoption pathways may take additional time. At the same time, manufacturers supporting EU MDR submissions may encounter earlier expectations to justify EO residual limits using the revised toxicological framework.
This creates a temporary environment where manufacturers may need to balance evolving international expectations against existing legacy acceptance approaches.
As a result, some organizations may choose to apply more conservative exposure assumptions during the transition period, particularly for globally marketed products. Approaches such as using lower body mass assumptions or selecting the most conservative calculated allowable limit may help support broader regulatory defensibility across multiple jurisdictions while regulatory expectations continue to evolve.
Ultimately, manufacturers will need to ensure that their rationale, assumptions, and exposure models are clearly documented and scientifically justified regardless of which implementation pathway is selected.
What Medical Device Manufacturers Could Be Facing
While the scientific intent of ISO 10993-7:2026 is clear, implementation presents several practical and regulatory considerations for medical device manufacturers.
One of the key implementation considerations will be determining applicability of the revised framework across product portfolios. Manufacturers may need to evaluate how the updated methodology could impact new product introductions, design or sterilization changes, manufacturing transfers, and future regulatory submissions.
Manufacturers may also face internal interpretation challenges as toxicology teams, regulatory affairs groups, sterilization engineers, and validation specialists work to align on appropriate exposure assumptions and allowable limit methodologies. Questions surrounding body mass assumptions, cumulative exposure scenarios, and concomitant device exposure considerations may require closer cross-functional collaboration than was historically necessary under the previous framework.
Another consideration is the increased complexity of acceptance criteria development. Under the previous framework, many EO residual limits could be applied using standard exposure categories and relatively fixed thresholds. The revised standard now requires a much deeper understanding of device-specific clinical use conditions, patient populations, and exposure duration assumptions. This creates additional pressure on manufacturers to ensure that risk assessments are both scientifically justified and regulatorily defensible.
For prolonged and long-term exposure devices, manufacturers may also encounter increased regulatory focus surrounding cumulative exposure and repeated device use. Products intended for neonatal, pediatric, or otherwise vulnerable populations may receive additional scrutiny, particularly when exposure assumptions are not clearly documented and justified.
In addition, organizations may determine that existing validation protocols, residual testing strategies, or acceptance criteria should be updated to better align with the revised framework. This can lead to the need for updated protocols, revised toxicological justifications, supplemental gap assessments, or enhanced documentation to support future submissions.
Perhaps most importantly, the revised standard reinforces the need for stronger collaboration between analytical laboratories, toxicologists, regulatory specialists, and sterilization validation teams. EO residual testing can no longer exist in isolation from toxicological interpretation. Quantitative results now require meaningful context in order to support a complete and defensible risk assessment.
A More Strategic Approach to Transition
The organizations that will navigate ISO 10993-7:2026 most effectively are not necessarily those that move the fastest, but those that approach implementation strategically.
A structured transition assessment can help manufacturers determine which products are likely impacted, where legacy justifications may remain acceptable, when updated allowable limit calculations may be necessary, how exposure assumptions should be documented, and whether current protocols and acceptance criteria remain appropriate.
This allows companies to prioritize resources appropriately while avoiding unnecessary rework and minimizing regulatory risk.
Rather than treating the revision as a blanket requirement to reassess all EO programs, manufacturers should focus on building scientifically defensible, product-specific rationales aligned with actual clinical exposure conditions.
Supporting Manufacturers Through the Transition
As the industry adapts to ISO 10993-7:2026, access to both technical testing capabilities and experienced regulatory guidance becomes increasingly important.
At Canyon Labs, we provide EO and ECH residual testing capabilities at both our Salt Lake City and Rochester laboratory locations, supporting manufacturers with analytical services aligned to the evolving expectations of the revised standard. Our teams understand that generating accurate residual data is only one part of the process—the interpretation and application of those data within the new toxicological framework are equally critical.
In addition to laboratory testing services, our consultants work directly with manufacturers to help navigate the practical implementation challenges introduced by ISO 10993-7:2026. This includes support with transition and applicability assessments, toxicological interpretation, allowable limit calculations, exposure scenario development, protocol and acceptance criteria updates, and regulatory submission readiness.
By combining analytical expertise with regulatory and toxicological consulting support, we help manufacturers develop practical, defensible strategies tailored to their products and intended use conditions.
The transition away from “one-size-fits-all” EO residual limits represents a significant evolution in medical device risk assessment. With the right technical and regulatory approach, manufacturers can adapt confidently while maintaining compliance, minimizing disruption, and supporting patient safety.
This is where Canyon Labs provides clear value. Our team brings dedicated toxicological expertise into the BEP and BER process from the beginning, providing a set of options that can be tailored to your needs. The most turn-key option is to have a Canyon Labs toxicologist write your BEP or BER from beginning to end, providing their expertise every step of the way and signing the final document as the author. Alternatively, a Sponsor may elect to write the BEP or BER themselves, with a Canyon Labs toxicologist reviewing the document at appropriate points and providing feedback and recommendations to ensure that the report is structured, justified, and documented in alignment with ISO 10993-1:2025 expectations. As an add-on option for this approach, a Canyon Labs toxicologist can co-sign the final document as a reviewer, demonstrating that the finished product was produced with the input of a qualified SME toxicologist.
By involving a toxicologist early in the BEP/BER process, Canyon Labs helps you reduce gaps, streamline submissions, and build documentation that is tailored to meet your specific regulatory needs. As agency expectations and international standard requirements continue to increase, having the right toxicological expertise involved is critical.