ETHOXOFUME 1000 (EtO): methyl bromide alternative update

Abstract

Ethylene oxide (C₂H₄O = EtO) is made from the oxidation of ethylene and over 15 million tonnes are produced annually. For over 80 years EtO has been used as a sterilant / fumigant. EtO is lethal to bacteria, viruses, moulds, insects and their eggs. Historically EtO was used in the fumigation of bulk grain. EtO is still widely used in “cold” sterilization of medical devices and instruments. With the precondition of destroying vented EtO at the completion of fumigation, EtO could be a niche methyl bromide (CH₃Br = MeBr) alternative. EtO is toxic by inhalation with an LD₅₀ of 330 mg.kg^-1 EtO is classified as carcinogenic to humans by the International Agency for Research on Cancer (IARC). Occupational Limits: TLV-TWA (1 ppm); OEL (UK)-LTEL (5 ppm). EtO is a colourless, highly flammable gas (Lower Explosive Limit (LEL) = 3 vol% in air) which liquefies at 10.9oC. To reduce flammability EtO is mixed 12 vol% EtO in carbon dioxide (CO₂). Onsite mixing of EtO and Air is an option, however the EtO must be kept below 54 g.m^-3 (3 vol%) – higher doses of EtO would require on-site mixing with CO₂ or N₂. Quarantine fumigations using ETHOXOFUME 1000 are carried out using vacuum chambers to treat non-food import and export commodities. On completion of the fumigation the EtO/Air mixture can be exhausted using a high pressure fan and destroyed in a “burner” where it is converted to CO₂ and H₂O. The Ct product for the control of various species of insects show that EtO on a weight basis (g.m^-3) has better efficacy than MeBr. A conservative recommended dose rate of 48 g.m^-3 results in a concentration of 1.2 vol% for MeBr and 2.7 vol% for EtO (this is less than the LEL of 3 vol%).

Keywords: Ethylene oxide, Fumigant, Sterilant, Insecticide, Incineration