Do you know how the ethylene oxide sterilization standard has changed?

A French intervention has led to the amendment of the international standard on ethylene oxide sterilization of medical devices. This blog post discusses what’s new and why.

Ethylene oxide (EO) is mercurial stuff. A gas produced by the vapour phase oxidation of ethylene, it’s a toxic, flammable and explosively unstable material with a normal boiling point of 10.5⁰C and high electrical conductivity.

More relevant in the current context, EO is also highly toxic to microorganisms, which is why it’s useful for sterilizing medical devices that won’t withstand heat or radiation.

However, its lethalness to microorganisms makes it highly toxic to humans. Specifically it’s a genotoxic carcinogen – meaning that it damages the genetic information within cells causing mutations that may lead to cancer.

So EO has unique and useful properties, but it’s also very volatile and dangerous stuff. Hence the care that needs to be exercised when EO is used to sterilize medical devices, and the existence of BS EN ISO 10993-7:2008+A1:2022 Biological evaluation of medical devices -- Part 7: Ethylene oxide sterilization residuals.

What does the standard do?

BS EN ISO 10993-7 specifies allowable limits for residual ethylene oxide (EO) and ethylene chlorohydrin (ECH) in individual EO-sterilized medical devices. It also gives procedures for the measurement of EO and ECH, and methods for determining compliance so that devices can be released. The standard also includes additional background information and informative annexes that include guidance and a flowchart showing how the standard is applied.

How the standard has changed

The allowable limits for ethylene oxide exposure were calculated using the method of toxicological risk assessment specified by ISO 10993-17 Biological evaluation of medical devices -- Part 17: Establishment of allowable limits for leachable substances, and have been in use for many years.

However, recently the French Competent Authority pointed out that the standard doesn’t contain limits that explicitly protect newborn babies. It was agreed by the international committee of experts that the standard therefore needed to be changed.

The result is this 2022 amendment. This makes explicit reference to “premature neonates, neonates and children”. At the same time, ISO has taken the opportunity to review the standard and make additional changes which clarify the document and bring it up to date with current technology and approaches. The result is a more comprehensive and useful standard which users should now obtain to replace the 2008 version.