EFHSS Questions and Answers - Question Q00152

Question concerning ETO (Ethylene Oxide) Sterilisation Procedure:

Residuals after 48 hours   EO < 250 ppm
Minimal Aeration time     ECH < 250 ppm

Residuals after 72 hours   EO < 250 ppm

The above is in relation to the sterilisation of Eye Spheres and Conformers.
Does this mean that the item concerned has to aerated longer than the usual 8 hours ? (ie: 48 hours or 72 hours on a shelf)

Look forward to your answer.

Thank you.

Lynne Cleary/CSSD/ Launceston General Hospital/Tasmania

Dear,

Questions Q00079 and Q00089 also treat the problem of EO desorption.

The determination of maximum permissible EO concentrations in a product at the time of use has shifted over the last years from a arbitrary value (equal or less then 1 ppm) to the more flexible approach of EN ISO 10993-7. Herein the permissible concentrations of EO are recommended in accordance with the intended duration of patient exposure.

It seems much more reliable and practical to me to handle the arbitrary value of 1 ppm, in a hospital environment, as maximum residual EO concentration. Not only because it is very difficult if not impossible to determine the residual EO concentration in a product but also because we can't predict how much EO the patient will be in contact with over a certain period of time or lifelong.

I think the limit of 1 ppm offers the patient more safety. Therefore I advise you to adapt aeration times and/or methods so you can meet the proposed values.

Best regards,
Wim Renders

Reference: "Desorption of Ethylene Oxide (EO) for Compliance with Limit Values", V. Herzog, Central Service, 4/2000.

Dear,

An interesting publication on EtO residuals is: "A guide to ISO 10993-7 and AAMI TIR-19 for EtO-sterilized devices" by W.Howard Cyr and Barry F. J. Page. You can find it under: www.devicelink.com/mddi/archive/00/02/007.html It's a comparison of ANSI/AAMI/ISO 10993-7;1995 with FDA's 1978 proposed rule for the maximum allowable levels of EtO, ECH, and EG in medical devices.

Kind regards,
Wim Renders