The current worldwide pandemic has impacted every aspect of our lives, which we are struggling to bring back to what we consider ‘normal.’ We have seen an impact on our social habits, our way of working and our economical balance, along with a changed perception on health. There has also been increased attention on the value of healthcare and medical device manufacturers, and the sudden dramatic increase of personal protective equipment (PPE) demand like face masks, gloves and protective suits.
Sterilization processes have always been essential for medical device industries but now they are assuming an even greater relevance for limiting infections, especially in an emergency situation of single-use device shortage.
One of the most adopted sterilization processes uses ethylene oxide (EO), a highly reactive, toxic and flammable gas capable of sterilizing at ambient temperature, preserving those medical devices which cannot be exposed to moisture or high temperatures -- like the ones made of polymers, plastics or those containing electronic components. The EO sterilization is assumed to play an important role in the battle against COVID-19, but, due to its intrinsic hazardous nature and carcinogenic effect on human beings, very high attention must be paid on possible residual levels.
During the pandemic, a shortage of filtering facepiece respirators has led some health care facilities to sterilize PPE for reuse. However, the Washington State Department of Labor & Industries issued a warning stating that EO sterilization is not approved by federal OSHA for use on personal protective equipment and should not be used to sterilize filtering facepiece respirators for reuse because this extremely hazardous toxic chemical poses a severe risk to human health.
This position is supported by the Centers for Disease Control and Prevention (CDC) which states, “Ethylene oxide is not recommended as a crisis strategy for cleaning filtering facepiece respirators as it may be harmful to the wearer.”
In this scenario, it becomes even more critical to rely on efficient and sensitive testing methods to ensure no residual EO is present on PPE and medical devices in general.
EO is absorbed by many materials, for this reason, following sterilization the item must undergo aeration to remove any residual. Guidelines have been promoted regarding allowable EO limits for devices that depend on how the device is used, how often, and how long in order to pose a minimal risk to patients in normal product use1.
Additionally, during the EO sterilization process, it is also possible the formation of 2-chloroethanol (or ethylene chlorohydrin, ECH)2, which is classified as a hazardous substance very toxic by inhalation and skin absorption.
The headspace (HS) sampling technique coupled with GC-FID (gas chromatography-flame ionization detection) analysis is a simple approach to quantify possible residues of ethylene oxide and 2-chloroethanol compounds in solid materials, with almost no sample preparation required.
ISO 10993.7-2008 (Biological evaluation of medical devices) and Chinese National Standards3,4 are reference guidelines setting limits for ethylene oxide and 2-chloroethanol in a variety of different materials. In particular, the residual limit for ethylene oxide on face masks is set to 10 µg/g.