Ethylene oxide is a fequently used and potentially dangerous sterilizing agent. Also known as EtO or EO, it is highly compatible with today’s polymer-based single use medical devices, procedure kits, surgical trays, etc., and is used for sterilization in many veterinary and animal surgical facilities. 

 

In the small-batch sterilizers used in animal surgical units, EO is usually delivered as a gas or a small liquid capsule that is opened and allowed to vaporize for each batch run. At normal room temperatures, EO is a colorless, highly flammable, toxic gas and improper or careless use can cause serious problems.

 

EO is a gas at room temperature with a boiling point of 10.7°C (51°F). It is colorless with a characteristic sweet odor, however if you smell it you are breathing a concentration hundreds of times greater than the exposure limit. The OSHA permissible exposure limit is only 1 ppm where the reported odor threshold is between 500 and 700 ppm. Therefore, odor is a very poor warning property for EO.

 

EO is also a highly flammable gas. The flammable limits in air are 3% to 100%, a very wide range. The vapor density is 1.5 (air=1.0) and if uncontrolled the vapors will tend to sink to the floor (or lowest available levels) and accumulate, spreading to the nearest ignition source.

 

Now, for the health effects. EO is a serious health hazard. Exposures usually occur by inhalation or skin absorption. Exposures to either the liquid or vapors can have severe results. Liquid EO can produce irritation or blistering of the skin or frostbite, from rapid evaporation and consequent cooling. In some persons, ethylene oxide exposure may result in allergic sensitization and future exposure may cause hives or a life-threatening allergic reaction.

 

Ethylene oxide has its own specific OSHA standard, 29CFR1910.1047. This standard covers all occupational exposures to EO and outlines the requirements for monitoring, medical examinations, training, and recordkeeping. Under the standard, OSHA has established an action level of 0.5 ppm and a permissible exposure limit (PEL) of 1.0 ppm, both based on eight-hour time weighted averages (TWA). There is also a short term exposure limit (STEL) of 5.0 ppm, a 15-minute average that employees shall never exceed. Periodic monitoring is conducted every six months for employees exposed at or above the action level and every three months for those exposed at or above the PEL. The appendices contain useful information on health and safety data, sampling and analytical methods, and workplace design and practices.

 

If ethylene oxide is used in your facility, potential exposures should be evaluated. First, take a close look at your equipment and how it is set up. Is the room or area appropriate with proper ventilation and exhaust and without conflicting uses? For general ventilation, is the room on dedicated single-pass air without recirculation? Is the area balanced slightly negative to adjacent spaces? Are there sufficient room air changes (normally calculated as air changes per hour, ACH, based on room volume and the cubic feet per minute, CFM, of supplied conditioned air)?

 

Additional assistance is available from the EtO Sterilization Association (http://www.eosa.org/) as well as the NIOSH and OSHA websites. In the case of areas where EO is used, ensure ample exhaust, sufficient room air changes, safe cylinder/material handling, and routine leak-check procedures. Finally, conduct periodic monitoring of the engineering systems and air concentrations.

 

From Sterilize That! by the Safety Guys