What is ethylene?

Ethylene: Medical Applications and Safety Considerations

Ethylene is a gaseous compound primarily used in medical settings as ethylene oxide (EtO), a sterilizing agent for heat-sensitive medical equipment, though it presents significant safety hazards including toxicity, carcinogenicity, and flammability. 1

Chemical Properties and Sources

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

• Molecular weight: 62 Da 1
• Colorless gas with minimal protein binding
• Highly flammable and can trigger explosive chain reactions 1
• Found in both anthropogenic and biogenic sources 2

Natural sources of ethylene include:

• Microbial activity in soil and marine environments
• Biological formation in various plant species
• Plant growth regulator that affects cell division and expansion 3

Anthropogenic sources include:

• Combustion of fossil fuels
• Forest and savanna fires
• Motor vehicle exhaust (largest contributor to urban ethylene levels)
• Industrial emissions 2

Medical Applications

Ethylene Oxide Sterilization

Ethylene oxide is the primary medical application of ethylene, used for sterilizing heat-sensitive medical equipment:

• Mechanism: Low pressure or subatmospheric ethylene oxide sterilizers operate at temperatures below 60°C, making them suitable for sterilizing flexible endoscopes and other heat-sensitive instruments 1
• Effectiveness: Among currently available sterilization methods, only ethylene oxide sterilization is both effective and compatible with GI flexible endoscopes 1
• Process requirements:
  • An EO venting cap must be fitted according to manufacturer's instructions
  • Instruments must be thoroughly cleaned prior to sterilization
  • Biological indicators are required for routine monitoring
  • Instruments must be placed in special disinfection bags or containers with internal indicators 1

Safety Concerns and Limitations

Health Hazards

Ethylene oxide presents significant health risks:

• Toxic in both liquid and gas forms
• Can cause serious eye irritation, sore throat, difficulty breathing, and blurred vision
• Carcinogenic with increased risk of breast and lymphohematopoietic cancers 4
• Requires strict environmental controls and specially trained staff 1

Practical Limitations

The use of ethylene oxide has several practical drawbacks:

• Lengthy processing time (1-7 days)
• Extended aeration period (8-12 hours) required to remove residual gas 1
• Not suitable for quick turnaround of instruments
• High flammability with risk of explosive chain reactions 1
• Few hospitals have ethylene oxide sterilizers due to safety concerns 1

Alternative Sterilization Methods

For medical equipment sterilization, alternatives to ethylene oxide include:

1. Gas Plasma:

   • Uses hydrogen peroxide gas plasma at low temperatures (<50°C)
   • Produces free radicals that interact with microorganisms
   • Requires special adapters for devices with lumens
   • Complete cycle takes only 75 minutes 1

2. Peracetic Acid (PAA):

   • Mixture of acetic acid and hydrogen peroxide
   • Wide antimicrobial spectrum against bacteria, spores, fungi, and viruses
   • More potent and faster-acting than glutaraldehyde and OPA
   • Environmentally friendly but potentially corrosive to metallic components 1

3. High-Level Disinfection (HLD):

   • Standard for most endoscope reprocessing
   • May require double HLD for endoscopes stored longer than recommended time 1

Environmental and Exposure Considerations

• Occupational exposures generally range up to 50-100 ppm for those working in horticultural, petrochemical, and fire/rescue industries 2
• Community-level personal monitoring has documented exposures of 3-4 ppb 2
• Indoor sources include environmental tobacco smoke, wood or propane fuel use, fruit storage, and cooking 2
• Recent research suggests potential association between environmental ethylene oxide exposure and increased risk of in situ breast cancer 4

Best Practices for Medical Use

When ethylene oxide sterilization is necessary:

• Follow manufacturer's instructions precisely
• Ensure proper ventilation and environmental controls
• Use appropriate personal protective equipment
• Document temperature and time of sterilization
• Perform thorough cleaning of instruments before sterilization 1
• Consider alternative sterilization methods when quick turnaround is needed 1

Ethylene oxide should only be used in settings with proper safety equipment, strict environmental controls, and specially trained staff due to its significant hazards 1.