Sterilants

The provision of good quality health services requires effective disinfection and/or sterilization of health care products to prevent transmission of infection. There is a range of commercially available sterilization methods including: heat (moist heat or dry heat), ionizing radiation (such as gamma, electron beam, x-ray radiation), alkylating processes (such as ethylene oxide (EO), formaldehyde) and oxidative processes (including hydrogen peroxide gas, gas plasma systems, liquid or gaseous peracetic acid, and ozone).

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The EO gas processes can be used to penetrate many types of packaging materials and internal areas of medical devices, destroy micro-organisms and then diffuse away from the product through the package. Following exposure, adequate aeration is essential after processing to achieve acceptable levels of residues. EO is toxic, mutagenic, carcinogenic, flammable and explosive, and increasingly more stringent regulations are applied to protect the environment and ensure worker safety. The fact that EO is still used as a sterilant, and its use growing in the industrial sector, is evidence that for numerous applications the benefits of its use outweigh these disadvantages.

EO can be used as a sterilant either alone or diluted with other gases to make non-flammable mixtures. A mixture of 12 per cent by weight EO and 88 per cent chlorofluorocarbon-12 (CFC-12) (12/88) had previously been widely used for this purpose. Hydrochlorofluorocarbons (HCFCs) were introduced as drop-in replacement for EO/CFC-12 mixtures but have been phased out in Europe. On an industrial scale, non-flammable mixtures can be created in situ within the sterilizer chamber using nitrogen. Non-flammable EO mixtures can be supplied for industrial or hospital use with carbon dioxide (CO2) as a diluent.

Hydrofluorocarbons (HFCs) have been investigated as alternative replacement diluents but have not been widely adopted for technical reasons and the environmental impact of the use of HFCs. In the European Union, the use of HFCs in sterilizing equipment is not currently explicitly excluded. One company in Poland supplies EO/HFC-134a (5.6 per cent by weight EO and 94.4 per cent HFC-134a) for use in hospital sterilizers. EO/HFC blends have also been investigated to replace EO/methyl bromide blends to fumigate, inter alia, archives and antiquities.