Dear Sirs,

Plastic material tends to absorb Ethylene Oxide Gas. How do you ensure that the transfusion/infusion sets which are EtO sterilised safe to use and devoid of EtO residue? When such large quantities are involved can each and every set be presumed safe to use without test? The toxic residue of EtO is known to inhibit certain bacterial growth. Won't this be leading to a false negative?How do you ensure that the sterility is complete. Which is the analytical method that can detect such low values?

Many countries have banned certain amines used in manufacture of Dyes & Chemicals which indirectly come in contact with human. Where as though the disadvantages of EtO Sterilisation are widely known and could have a direct impact on the human life, no action is being initiated to ban its use and the method is persisted. Is there any particular reason or is cost the only criteria?

Thanks,

Viraj Bahutule
Mumbai

Dear Viraj Bahutule,

You address a series of issues, which go beyond EtO sterilization. Whatever process is used to sterilize whatever product, one has to ensure that the outcome is "sterility", that the product is safe for use afterwards and that its functionality is guaranteed. Nevertheless I have tried to give an answer to all your questions below.

• Plastic material tends to absorb Ethylene Oxide Gas.
  True; to different degrees depending on material. The question on EtO residues has been addressed already in answers 152, 89, 79. In principle it is the responsibility of the manufacturer of the product to be sterilized to give guidance, as he is the only one who knows the exact material composition.
   
• How do you ensure that the transfusion/infusion sets that are EtO sterilised safe to use and devoid of EtO residue?
  By testing (e.g. see ISO 10993-7 for limits and methods).
   
• When such large quantities are involved can each and every set be presumed safe to use without test?
  No! Only if the sterilization/desorption process has been validated, the type and amount of testing required can be established and potentially reduced - but never eliminated.
   
• The toxic residue of EtO is known to inhibit certain bacterial growth. Won't this be leading to a false negative?
  If this refers to biological indicators: in theory yes, in practise no.
   
• How do you ensure that the sterility is complete?
  Only by direct testing - which would make your product unusable. Therefore the SAL 10^-6 has to be established by methods described in various documents (e.g. local, CEN and ISO standards, pharmacopoeias and FDA regulations).
   
• Which is the analytical method that can detect such low values?
  If this refers to EtO residues see ISO 10993-7.
   
• Many countries have banned certain amines used in manufacture of Dyes & Chemicals which indirectly come in contact with human. Where as though the disadvantages of EtO Sterilisation are widely known and could have a direct impact on the human life, no action is being initiated to ban its use and the method is persisted. Is there any particular reason or is cost the only criteria?
  All sterilization methods have advantages and limitations. EtO is proven for its efficiency and is the No.1 industrial method worldwide. Certain precautions have to be taken to avoid unnecessary risk of exposure to e.g. workers, but there are many such means known and available like closed cycles and abators. It is the way you handle a substance that makes it potentially dangerous: if you can't swim, don't jump into water.

The pro's and con's of the various sterilization methods like steam, EtO, irradiation, LTSF, H₂O₂ gas have to be carefully judged before selecting one for a certain product. Factors like: temperature, humidity level, penetration capabilities, compatibility with products, costs, etc, etc. There is no single universal method.

Kind regards

Klaus Hahnen
Senior Technical Service Specialist
Sterilization Assurance Products
3M Laboratories (Europe), Neuss, Germany