What is ethylene?

Ethylene: Properties, Uses, and Medical Implications

Ethylene is a flammable, colorless gas used primarily as a sterilizing agent for heat-sensitive medical equipment and as an industrial chemical, with significant toxicity concerns requiring strict safety protocols during handling and use.

Chemical Properties and Sources

Ethylene is a small, water-soluble molecule with the following characteristics:

• Colorless gas with minimal toxicity in its pure form 1
• Molecular weight of 62 Da 2
• Highly flammable and can trigger explosive chain reactions 2

Ethylene is found in various environments:

• Natural sources: Produced by microbial activity in soil and marine environments, and formed biologically in many plant species 1, 3
• Anthropogenic sources: Burning of fossil fuels, forest fires, vehicle exhaust (largest urban contributor), and industrial emissions 1
• Indoor sources: Environmental tobacco smoke, wood or propane fuel use, fruit/vegetable storage, and cooking 1

Medical Applications: Sterilization

Ethylene oxide (EtO) is primarily used in healthcare for sterilization purposes:

• Sterilization of heat-sensitive equipment: Among currently available sterilization methods, only ethylene oxide sterilization is both effective and compatible with flexible gastrointestinal endoscopes 2

• Process requirements:

  • Low pressure or subatmospheric ethylene oxide sterilizers operating at temperatures below 60°C 2
  • EO venting cap must be fitted according to manufacturer's instructions 2
  • Instruments must be thoroughly cleaned and suitably packaged 2
  • Biological indicators required for routine monitoring 2

• Major limitations:

  • Long processing time (1-7 days) including aeration period of 8-12 hours 2
  • Not suitable for quick turnaround of instruments 2
  • Requires strict environmental controls and specially trained staff 2

Health and Safety Concerns

Ethylene oxide exposure poses significant health risks:

• Acute toxicity: Eye irritation, sore throat, difficulty breathing, and blurred vision 2
• Chronic toxicity: Increased risk of cancer, particularly linked to breast cancer and lymphohematopoietic cancers 4
• Environmental exposure: Studies have shown increased risk of breast cancer (particularly in situ) associated with proximity to EtO-emitting facilities 4
• Occupational exposure: Documented in horticultural, petrochemical, and fire/rescue industries, with levels generally ranging up to 50-100 ppm 1

Alternative Sterilization Methods

For medical equipment sterilization, alternatives to ethylene oxide include:

1. Gas plasma sterilization:

   • Uses hydrogen peroxide gas plasma at low temperatures (<50°C) 2
   • Produces free radicals that disrupt microorganism function 2
   • Limitations: Not suitable for devices with very long narrow lumens or those closed at one end 2
   • Cycle time of approximately 75 minutes 2

2. Peracetic acid (PAA):

   • Mixture of acetic acid and hydrogen peroxide with strong antimicrobial properties 2
   • More potent and faster-acting than glutaraldehyde and OPA 2
   • Environmentally friendly as it degrades into acetic acid 2
   • Potential for corrosion of metallic components with long-term exposure 2

3. High-level disinfection (HLD):

   • Alternative to sterilization for semi-critical devices 2
   • Double HLD may be required for endoscopes stored longer than recommended time 2

Clinical Considerations

When dealing with ethylene oxide in clinical settings:

• Manual cleaning of endoscopes remains essential before any automated cleaning or disinfection 2
• Ethylene oxide sterilization must be performed after high-level disinfection 2
• Temperature and time of sterilization should be documented and follow manufacturer's instructions 2
• Personal protective equipment is essential when handling ethylene oxide 2

Conclusion

While ethylene oxide is effective for sterilizing heat-sensitive medical equipment, its use requires careful consideration of safety protocols due to its toxicity and flammability. Alternative sterilization methods may be preferable when quick turnaround is needed or when safety concerns are paramount.