Hydrogen Peroxide Risks vs Ethylene Oxide Risks

ChemDAQ Continuing Education Program

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How well would you do on a quiz about Hydrogen Peroxide (H2O2) & Ethylene Oxide (ETO)? What if your LIFE depended on it? Even though you'll likely never have to take a life or death quiz about different chemicals (thankfully!), understanding how these particular chemicals are used in your Sterile Processing department can definitely have huge implications for your short- and long-term health. In addition to protecting yourself, chemical education ensures your department and facility are compliant with FDA, EPA, and OSHA legal requirements regarding safe use, labeling, and training regarding these chemicals. 

In this 3 CE continuing education series, the ChemDAQ team will provide an important comparison between H202 & ETO sterilant chemicals and outline how they can be used safely with appropriate training, tools, and equipment. 

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Ethylene Oxide (or EtO) is a gas sterilant widely used in hospitals and sterilization facilities, particularly in the mass sterilization of disposable supplies (like syringes).  It is used as an alternate to steam sterilization for items that are heat sensitive or moisture sensitive. Sterilization in EtO can take anywhere from 14 hours to 48 hours due to the need for longer exposure times and the need for thorough aeration (degassing). EtO is highly reactive and sterilizes by attacking the cellular proteins and nucleic acids of microorganisms. However its reactivity, which makes it an effective sterilant, also means that it is hazardous to human health.  Ethylene Oxide is a known human carcinogen, mutagenic, and presents reproductive and neurological hazards. 

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Ethylene Oxide is a colorless, odorless gas used in low temperature sterilization. As a gas, it can easily penetrate packaging to sterilize items at a low temperature. The way EtO gas sterilizes a device is by disrupting the cellular metabolism and reproduction of microorganisms on the device. EtO is an alkylating agent, meaning it adds an alkyl group to the proteins of the cell. By attacking the proteins, DNA, and RNA of microbial cells, Ethylene Oxide effectively kills microbial life. EtO for sterilizers is usually found mixed with other gasses, such as CO2 or hydrochlorofluorocarbons (HCFC) in various concentrations. Because EtO presents a human health hazard, preventative measures are necessary to prevent exposure. Chronic exposure to EtO has been linked to cancer, mutagenic changes, reproductive effects, and neurotoxicity.

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EtO is commonly misunderstood. Here are some myths about EtO;

“Hydrogen peroxide and ozone are much safer than EtO.”

  • Sterilant chemicals are designed to kill all life, whether within or without the sterilizer and therefore chemicals that are used in a sterilizer will cause harm to humans who are exposed to them. 

“EtO isn’t as good as newer modalities of sterilization.”

  • The technology for delivering EtO has dramatically improved, and EtO remains to be a very effective yet delicate sterilization process with broad material compatibility. 

“EtO sterilization is only good for a few antiquated items.”

  • EtO can be used to sterilize many materials with the exception of food, drugs, or liquids. EtO is very gentle on delicate instruments, and it does not require any special packaging different from the other sterilization modalities. EtO can accept paper/plastic pouches as well as sterilization wrap and rigid containers. 

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Hydrogen Peroxide (H2O2) is a gas sterilant widely used in hospitals, usually for surgical instruments which cannot handle the high-temperature or moisture of steam sterilization. Advantages to Hydrogen Peroxide sterilizers are that they generally have short exposure cycles, there is not an extended aeration period, and the equipment only requires power as a utility (not water, compressed air, or steam). A disadvantage is that cellulose-based products such as paper cannot be used in the sterilizer. The Hydrogen Peroxide used in gas sterilization can be up to 90% concentration, which is much stronger than the concentrations found in other products used in daily life.  Items like pharmaceutical grade H202, detergent bleach, and contact lens cleaner all have concentrations lower than 8%. 

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Hydrogen Peroxide is a strong oxidiser; it reacts easily with other substances, accepting the electrons of other substances and killing microbial life by destroying the cell walls. Hydrogen Peroxide (H2O2) slowly decomposes into water (H2O) and oxygen (O2). Hydrogen Peroxide is colorless, odorless, and unstable. It is highly flammable, and spontaneous ignition can occur if it comes in contact with flammable substances like paper, wood, oil, or cotton. Hydrogen Peroxide at high concentrations is hazardous to human health.  Hydrogen peroxide exposure takes place through inhalation of mist or through skin or eye contact. It will cause irritation, possibly painful blisters, and can cause permanent eye damage. H2O2 has also been shown to be an animal carcinogen and a mutagen. 

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H202 is commonly misunderstood. Here are some myths about H2O2

“This Hydrogen Peroxide sterilant is just like the Hydrogen Peroxide I buy at the store.”

  • The concentration for pharmaceutical hydrogen peroxide is around 3%, while the concentrations used in the sterilizer is between 50-60% concentration. 

“Hydrogen Peroxide as a sterilant is not hazardous.”

  • Both H2O2 and EtO pose serious health hazards if humans are exposed to the chemical, and H202 actually has a lower IDLH (Immediately Dangerous to Life and Health) limit than EtO. 

“Monitoring for H2O2 isn’t necessary since the sterilizers are very safe.”

  • While H2O2 sterilizers are designed to be very safe and prevent chemical exposures to the operators, equipment malfunctions and human error can lead to dangerous exposures. 

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The Occupational Safety and Health Administration (OSHA) has defined Permissible Exposure Limits (PELs) for many chemicals. Most of these PELs were adopted in the 1970s from the Threshold Limit Values (TLVs) of the American Conference of Governmental Industrial Hygienists (ACGIH). Both EtO and H2O2 have a PEL of 1.0 ppm as a Time Weighted Average (TWA) of 8 hours.  The Time Weighted Average means that the person must not be exposed for a sustained amount of time (an average over an 8 hour period).  

For more information about OSHA’s PELs, see 


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The Hazard Communication Standard (HCS) (29 CFR 1910.1200) from OSHA is a general standard for the use of chemicals in the workplace. Hydrogen Peroxide is listed in this general standard, requiring employers to provide a written hazard communication program regarding the chemical.  This is usually met by having access to chemical Safety Data Sheets that meet the requirements of the OSHA HCS. EtO has its own standard, 29 CFR 1910.1047 which includes many sections similar to the HCS as well as EtO specific material. The HazCom standard explicitly tells employers that they have to train their employees on the “methods and observations that may be used to detect the presence or release of a hazardous chemical in the work area” [1910.1200(h)(3)(i)].

For more information about OSHA’s Hazard Communication, see https://www.osha.gov/dsg/hazcom/

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The Immediately Dangerous to Life or Health air concentration values (IDLH values) are developed by the National Institute for Occupational Safety and Health (NIOSH). The IDLH value for Ethylene Oxide is 800 ppm air concentration, while the IDLH value for Hydrogen Peroxide is only 75 ppm air concentration.  This means that exposures of 75ppm of H2O2 or 800ppm of EtO could cause significant damage to a person’s health, perhaps even fatal damage.

For more information about NIOSH’s IDLH, see


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The Threshold Limit Value (TLV) is a determination published by the ACGIH (American Conference of Governmental Industrial Hygienists) that exposure at or below the level of the TLV does not create an unreasonable risk of disease or injury. These TLVs represent the opinion of the scientific community based upon data, and they are not regulatory standards.  In many cases (as with EtO and H2O2), OSHA has adopted the recommendation of the TLV in determining the Permissible Exposure Limit (PEL). The TLV for H2O2 and EtO are both 1.0 ppm over an 8 hour Time Weighted Average.  However, the ACGIH also says that “Excursions in worker exposure levels may exceed 3 times the TLV-TWA for no more than a total of 30 minutes during a workday, and under no circumstances should they exceed 5 times the TLV-TWA, provided that the TLV-TWA is not exceeded.” This means that the maximum exposure to hydrogen peroxide should be no more than 5 ppm.

For more information about ACGIH’s TLVs, see


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The Joint Commission publishes standards to measure, assess, and improve the performance of healthcare organizations.  In their Environment of Care (EC) standards, EC.02.02.01 states “The hospital manages risks related to hazardous materials and waste.” Within this category, Element of Performance (EP) #9 states “The hospital minimizes risks associated with selecting, handling, storing, transporting, using, and disposing of hazardous gases and vapors.” Element of Performance (EP) #10 states “The hospital monitors levels of hazardous gases and vapors to determine that they are in safe range.” These Joint Commission standards indicate that H2O2 and EtO should be carefully managed to minimize risk, including monitoring of hazardous gases and vapors.

For more information about Joint Commission’s Environment of Care standards, see


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The Association for the Advancement of Medical Instrumentation (AAMI) is a nonprofit organization comprised of industry professionals for the purpose of developing consensus standards for the medical device industry. AAMI standard ST41 is about “Ethylene Oxide sterilization in health care facilities: Safety and effectiveness.” ST41: B. states “For the health and safety of employees, AAMI recommends continuous monitoring of the workplace environment.” AAMI standard ST58 is about “Chemical sterilization and high-level disinfection in health care facilities.” ST58 states “Vapor monitoring is recommended if there is the potential for the vapor concentration to exceed the OSHA PEL.” 

For more information about AAMI, see https://www.aami.org/home

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Both Hydrogen Peroxide and Ethylene oxide are primary irritants, meaning they cause inflammation and other evidence of irritation with people when exposed to unsafe concentrations of these chemicals.  Both cause eye irritation and cause respiratory distress when inhaled. Both have been confirmed as carcinogens in animals, with EtO also being categorized as a known human carcinogen. According to AGCIH, it is unknown if Hydrogen Peroxide has a carcinogenic effect on humans. 

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These exposure studies show the importance of monitoring:

An ASP Published article found that various sterilizers emitted up to 20 ppm of H202 vapors that escaped after the chamber door was opened. See the full article here: https://www.asp.com/education/case-studies/comparison-study-of-environmental-hydrogen-peroxide-levels

An article by Steris titled “Safety in Central Service: Management Responsibility,” points out that if monitoring of vapors is required, a plan should be reviewed that may include both continuous monitoring and personal monitoring devices. See the full article here: https://university.steris.com/resources/safety-in-central-service-management-responsibility/

A study conducted by Tokyo Healthcare University Postgraduate School found that H2O2 concentration inside a sterilizer immediately after the end of the cycle, when healthcare workers would be reaching in to remove the load was very high (13 ppm – 60 ppm). See the full study here: http://www.deconidi.ie/html/conf/wfhss-conference-2012/lectures/wfhss_conf20121121_lecture_sp_s702_en.pdf

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One proposed solution to hazardous chemical monitoring is badge monitoring. Badges provide a retrospective Time-Weighted Average by measuring how much a person was exposed during the time that person wore the badge.  The badges are sent off for analysis and return with results two weeks later.  This is an accepted method of monitoring, but it is not the best solution for preventing harm to employees.  It would be much better to detect a hazardous gas leak in the moment and prevent exposure, than for someone to discover 2 weeks later that they had been exposed.  

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Any time there is risk of splashes from liquid EtO or H2O2, workers should wear splash-type goggles and appropriate skin protection.  This includes gloves made of nitrile, PVC, or neoprene and impervious clothing such as an approved splash protective suit. Approved boot covers made of NBR, PVC, Polyurethane, or neoprene would be used to cover shoes.  When handling sterilant for a particular sterilizer or re-processor, consult the manufacturer’s instructions about what kind of PPE is required for handling the sterilant. If concentrations in excess of 10 ppm are expected, employees should use a NIOSH/DHHS approved self-contained breathing apparatus.

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In order to protect your workers from hazardous vapor exposure, follow these steps:

Elimination – If possible, eliminate potential hazards by removing them entirely from the area (not practical for H2O2 or EtO).

Substitution – If possible, replace the hazard with something safer. The belief that H2O2 is safer than EtO has led many hospitals to switch from EtO to H2O2.

Engineering Controls -  Isolate people from the hazard using barriers or dedicated exhaust.

Personal Protective Equipment – Provide appropriate PPE to protect workers from substances they may encounter.

Preventative Maintenance – Keep sterilizers and re-processors in top shape to help prevent machine malfunctions.

Continuous Monitoring – Monitor the environment to ensure a safe workplace. Odor is an unreliable indicator of the presence or concentration of EtO or H2O2. 

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To protect workers from hazards in the workplace, it is the responsibility of management to provide education and training about the safe operation of equipment and the safe handling of hazardous chemicals.  This means that employees should receive training and have access to device and sterilizer manufacturer’s instructions and know what to do in a malfunction.  Employees should also have access to chemical Safety Data Sheets (SDS) and be trained how to access them and read them.  Additionally, team members should be trained how to interpret the various air monitoring systems and the exposure limits of hazardous chemicals.

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The Manufacturer and User Facility Device Experience (Maude Database) is an FDA database that contains “adverse event [reports] involving medical devices.”

Event Description:

The facility reported that an employee experienced a burn while handling items that were processed in a VPro Max 2 sterilizer.

A service technician found the unit to be operating according to specification; no repairs were required, and the unit was returned to service.

Facility personnel confirmed that the employee was not wearing proper PPE, specifically gloves, while operating the sterilizer.

The sterilizer operator manual states, "danger - chemical injury hazard: any visible liquids in the chamber or on the load must be treated as concentrated hydrogen peroxide.”

The user facility personnel should ensure all instruments are properly dry prior to placement in the v-pro max 2 sterilizer.

Residual H2O2 may remain at cycle completion or when cycle abort occurs.

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The Manufacturer and User Facility Device Experience (Maude Database) is an FDA database that contains “adverse event [reports] involving medical devices.”

Event Description:

A customer reported an odorless vapor/smoke emitting from the Sterrad® 100NX sterilizer, and one healthcare worker experienced irritation, burning, and itchiness in the eye.

The healthcare worker took off his contacts to rinse and flush eyes; the reaction lasted 4 hours.

The healthcare worker also had a light headache which lasted one hour.

The healthcare worker did not receive medical attention/treatment for his symptoms.

The customer was advised to clear the facility and shut down the unit until serviced.

A field service engineer was dispatched and replaced the adapter converter, catalytic converter, oil mist filter and vacuum pump oil to resolve the smoke/haze issue.

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The true solution to hazardous gas monitoring is Continuous Monitoring, which protects workers in real time. It gives a real-time measurement in ppm of the employees' workspace, as well as providing the concentration in 15-min and 8-hour TWAs. ChemDAQ monitors have built-in low level, high level, and action level alarms to notify staff if concentrations reach unsafe levels. They also have impending alarms that warn staff that the exposure is trending towards the PEL being exceeded, preventing exposure, not just reporting it.  

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As we wrap up this series on Hydrogen Peroxide & Ethylene Oxide sterilant chemicals we hope you realize how dangerous both of these chemicals can be to your personal health and the health of your healthcare team members. While unmistakably dangerous if exposed, the good news is that there are tools and equipment available to the industry that can safely enable Sterile Processing and Endoscopy users to work around these chemicals with confident compliance.  

Wherever you are on your journey to chemical safety in your department, it is critically important to involve and listen to the voices of frontline technicians who are most at-risk for injury and exposure. No decision is as personal as personal safety, and no technician should have to work in an environment they feel is unsafe.

In this 3 CE continuing education series, you were able to see a small part of the chemical puzzle that makes up our industry.

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