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June 2003 Consultations on the Risk Management of Ethylene Oxide used for Sterilization in the Healthcare Sector

Degradation/Decomposition Products of Ethylene Oxide in the atmosphere

The following is a response to a question asked at the June 2003 consultation meetings related to the degradation/decomposition products of ethylene oxide in the atmosphere, and the potential human health risks posed by these products.

Ethylene oxide (ETO) can degrade in air and water by the process of radical formation and hydrolysis. Depending on presence of other chemical species, this can lead to the formation of glycols (eg. ethylene glycol), halogenated alcohols (eg. ethylene chlorohydrin), methane, aldehydes, ethylene, and polymers of ETO.

Most of these substances would not be of a significant human health concern due to their 1) low inherent toxicity (eg. ethylene/methane) or 2) extremely low levels in comparison to ethylene oxide (aldehydes).

The two substances that would be of most concern are ethylene chlorohydrin and ethylene glycol.

Ethylene oxide reacts with water to produce ethylene glycol. Ethylene glycol is considered to have adverse health effects if taken orally, or if exposure occurs by inhalation, but only at significant volumes or concentrations respectively. In the liquid form, ethylene glycol is an irritant to the skin and eyes. As a breakdown product of ETO, ethylene glycol would be produced at much lower amounts than ETO, therefore the health impacts of the former would be a much more significant health concern.

In contrast, like ethylene oxide, ethylene chlorohydrin has carcinogenic potential. Ethylene chlorohydrin is formed from ethylene oxide in the presence of chlorine bearing substances. Ethylene oxide is permitted to be used in Canada as a fumigant on whole or ground spices, but only at concentrations which do not give rise to residual ETO following processing.

Ethylene oxide is not permitted to be used in spice mixtures containing salt, due to the potential for formation of the ethylene chlorohydrin byproduct. The use of ETO in spices, and hence the potential development of byproducts such as ethylene chlorohydrin is currently being reviewed by Health Canada.

The use of ethylene oxide on medical/pharmaceutical products which contain chlorine, may lead to trace amounts of ethylene chlorohydrin, and therefore, it is important to use evacuation of air or flushing with air (or a combination of both) to remove ETO and its byproducts from sterilized products.

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