Striving to provide quality care in a healing environment, healthcare facilities are taking a closer look at methods of sterilization and high-level disinfection for reusable medical equipment. Prevalent practices, including the use of ethylene oxide and glutaraldehyde, are not without safety and environmental impacts. Factoring in expensive and often incompatible instruments, quick turnaround needs and regulatory compliance, there’s no simple solution to sterilization and high-level disinfection. How can we balance infection control requirements with a healing environment?

According to the Centers for Disease Control and Prevention, healthcare-acquired nosocomial infections account for 70,000 annual deaths. While sterilization is done in a facility’s Sterile Processing Department, high-level disinfection can occur many places throughout a facility.


Critical items—those that enter the sterile cavity of the body—require destruction of all microorganisms, including bacterial spores. These care items include surgical instruments, implants, cardiac catheters, arthroscopes and laparoscopes. Sterilization by steam is slow and can damage high-tech equipment. Ethylene oxide, (EtO) is a known reproductive toxin and suspected human carcinogen. Its popularity has taken a plunge because of cost, risk, and hazards. Many facilities use multiple systems within one setting, striving to meet needs while reducing toxicity.

Heat- and moisture-sensitive instruments must be sterilized by ethylene oxide or one of the alternatives discussed below. Many endoscope manufacturers are now developing or producing scopes that can be steam sterilized.

Some facilities contract with third-party EtO sterilization services to sterilize heat- and moisture-sensitive instruments. For example, Kaiser Permanente found that this service offers advantages (consolidation of a toxic material into one well-controlled environment; potentially reduced liability) but at a premium price. Consequently, Kaiser Permanente has either eliminated EtO sterilization (by looking into finding disposable alternatives and/or alternatives that can be reprocessed by other means) or consolidated EtO sterilization within regions, so that the few centers retaining EtO sterilizers use them at full capacity.

Alternatives to ethylene oxide

Peracetic Acid. Thirty-five percent peroxyacetic acid (or peracetic acid) is classified as a highly toxic material, a Class II or III Organic Peroxide (by definition, <43% peroxyacetic acid); a Class 2 Unstable (reactive) Material (contains 6.5% hydrogen peroxide in equilibrium with peroxyacetic acid and acetic acid); and a Class II Combustible Material (flash point = 115°F, above 100°F but below 140°F). Precautions are necessary for working with this material. The packaging of its single use canisters is designed to “burp off” small amounts of chemical vapors, so canisters should be stored in well-ventilated areas. As many as six cases can be kept on open shelves in the same fire-rated areas if the area is sprinklered, but the room must not allow air to return to other occupied areas of the building. Reports of burns to employees who have been sprayed by incorrectly loaded reprocessors and by reprocessors opened while in cycle dictate that emergency eyewash facilities be available in the immediate work area.

Because the process is wet, if the instrument tray is not covered and the instrument is not used within 2 hours of reprocessing, it is no longer considered a sterile instrument. For this reason, this reprocessor has been termed a “just-in-time” sterilization process. Indeed, many bacteria double their population in a wet environment within 20 minutes, so it is advisable to use the instrument immediately or dry it thoroughly using an alcohol purge followed by forced air drying. Once alcohol has been introduced to the instrument, however, it is no longer considered a sterile instrument, but only a high-level disinfected instrument.

Hydrogen Peroxide Plasma Gas. Some sterilizers use hydrogen peroxide in a sealed cassette at a 50% liquid concentration. The liquid hydrogen peroxide is vaporized by radio frequency into a highly reactive plasma gas inside the sealed evacuated chamber. Although hydrogen peroxide is a strong oxidizer and can cause burns on contact, the double-sealed ampoules in the multidose cassette are not pierced until the sterilizer is under vacuum. It is impossible for an employee to open the sterilizer during a cycle, so there is no chance of worker exposure to the hydrogen peroxide liquid or the plasma gas. The sterilizer requires no special ventilation or utilities to operate, and water vapor is its only waste product.

The single biggest drawback to this technology is that it is limited to processing single channel flexible endoscopes with Teflon or polyethylene lumens of 850 mm length or less. It can, however, process a variety of heat- and moisture- sensitive instruments, including esophageal dilators, ophthalmic lenses, ultrasound probes and video cameras and couplers, surgical power equipment and their batteries.

Ozone. This new technology generates ozone from on-site oxygen, water, and electricity. Ozone is an oxidative gas the odor of which is readily detected at levels far below those that cause adverse human health effects. Ozone is a respiratory system irritant and a priority pollutant contributing to the formation of smog. It is therefore a public health concern. All the ozone in the sterilizer is theoretically converted to water vapor, requiring no special ventilation or utilities, although

it would be prudent to place the sterilizer in an area of negative-

pressure, nonrecirculating exhaust. This low-temperature sterilization process takes four hours, a period comparable with steam sterilization, but is able to process many heat-labile materials (except for latex, Kraton, and ether-based polyurethane; textile fabrics, copper and its alloys, zinc, or nickel are not recommended). The ozone system can process some lumened devices, such as arthroscopes, laryngoscopes, laparoscopes, resectoscopes, hysteroscopes, and bronchoscopes, as well as all types of urological scopes. It can also process ophthalmic lenses, cables and cords, power batteries, and Doppler probes.

High-level disinfection

Semi-critical items are defined as instruments that make contact with but do not penetrate mucous membranes and do not penetrate normally sterile areas of the body. Devices in this category must be cleaned and high-level disinfected between patients. Examples of semicritical items include flexible fiberoptic endoscopes, bronchoscopes, cystoscopes, vaginal and prostate endocavity probes, and laryngoscopes. Because of high equipment prices and the need for quick turnaround, high-level disinfection is often performed in the immediate treatment area.

A common agent for high-level disinfection is “cold sterilant” glutaraldehyde. This chemical has many drawbacks: Glutaraldehyde is an irritant, can induce asthma and respiratory sensitization, and can cause dermatitis. Workers complain of shortness of breath, irritation of mucous membranes and skin rashes. Morale can be lowered when aerosolized vapors irritate staffers and their complaints go unresolved. Some nurses who share an acquired sensitivity to chemicals and fragrances attribute this sensitivity to workplace exposure to glutaraldehyde.

Exposures can be dramatically reduced and symptoms virtually eliminated through the use of local exhaust ventilation and proper protective equipment, including goggles, face shields, aprons, and nitrile or rubber gloves. Latex surgical gloves do not provide adequate protection from dermal contact and should not be used. Surgical masks provide poor protection from disinfectant vapors and should also not be used; if respiratory protection is needed, the appropriate selection should be made based on the anticipated exposure levels.

Alternatives to glutaraldehyde

An alternative for high-level disinfection, developed and approved by the FDA in 1999, is 0.55% ortho-phthalaldehyde (OPA). This product achieves high-level disinfection in 12 minutes, versus glutaraldehyde’s 45 minutes. In a heat-controlled automatic endoscope reprocessor, OPA is effective in 5 minutes, versus 20 minutes for glutaraldehyde. OPA is less irritating to staff’s mucous membranes and does not vaporize readily, although little human toxicological research is available. The National Toxicology Program will be evaluating the chronic and acute health effects of OPA in their upcoming research agenda.

While the faster soak time and reduced vapor are improvements, OPA is not perfect. In 2004, allergy literature reports of allergic reactions in bladder cancer patients undergoing multiple cystoscopies using cystoscopes that had been reprocessed in OPA prompted Johnson & Johnson to modify its 510(k) label and contraindicate OPA for reprocessing all urological instruments used to treat patients for bladder cancer. In addition, the label states that in rare instances healthcare workers have experienced irritation or possible allergic reaction that may be associated with exposure to Cidex OPA. According to the manufacturer, “in the majority of these instances, healthcare workers were not using it in a well-ventilated room or not wearing proper personal protective equipment.”1

Additionally, OPA is 6,500 times more toxic to aquatic life than glutaraldehyde, requiring neutralization with glycine before drain disposal. (In California, glutaraldehyde is just over the threshold of being considered nonhazardous to aquatic life after its 14-day use life.) Check with your state regulators for proper sewer disposal of any high level disinfectant or chemical.

Kaiser Permanente employed the precautionary principle when dealing with OPA even before the reports of skin sensitization surfaced, due to the lack of acute or chronic human health data available for the product on its launch. Kaiser uses the same engineering, administrative and personal protective controls for OPA as it does for glutaraldehyde. Kaiser’s policy is to consolidate and isolate reprocessing rooms to areas of the building that have adequate general dilution ventilation (10-12 air changes per hour), that do not recirculate exhaust air to other areas of the building, that maintain a negative pressure relationship to adjacent spaces, and that are equipped with local exhaust ventilation or ductless fume hoods over soaking trays, tubes, and/or washers.

Concentrated OPA. In mid-2007, Advanced Sterilization Products (ASP) launched a fully automated washer and disinfector, a promising technology which purportedly eliminates the need for manually brushing the endoscope channels before reprocessing. The washer/disinfector uses a 5% concentrated OPA solution that is automatically diluted from a sealed bottle and neutralized before disposal to drain. Since the disinfectant is not reused, there is no need to manually test the solution’s microbial effectiveness with a test strip. The unit is able to monitor how much fluid is flowing through each channel during the processor cycles and provides a printed record at the end of all cycle parameters. The unit is also equipped with an alcohol and compressed air cycle to facilitate drying. This technology promises to relieve staff of the repetitive tasks of manually brushing channels and leak-testing endoscopes. While the promised benefits are certainly impressive, ASP is still in the process of answering concerns about the handling of alcohol waste, whether flammable atmospheres are created in the alcohol purge phase and whether processor lid gasketing eliminates the need for local exhaust ventilation. Any excess concentrated OPA would of course need to be disposed of as hazardous waste.

Diluted Peracetic Acid. Another manufacturer, Steris, is also marketing a high-level disinfector, one that generates a dilute peracetic acid solution from a measured amount of bulk dry chemical mixed with water inside the processor and circulated throughout the processor and device lumens under pressure. The processor washing phase does not replace manual pre-cleaning using a brush. The disinfector eliminates personal contact with chemical components by using a sealed bag for both the enzymatic detergent and disinfectant. The chemicals are not reused, so there is no need to manually test the solution’s effectiveness. The waste from each cycle is purportedly nonhazardous. In addition, it is not possible to open the disinfector during a cycle, which eliminates skin exposure.


Regardless of what technology is in use, material compatibility is a must. The reprocessing algorithm (figure 1) is helpful in identifying the sterilization and disinfection options for various pieces of equipment. Manufacturers stipulate the sterilization processes approved for each device. Make sure to consider reprocessing requirements and compatibility when purchasing new equipment.

The reprocessing algorithm defines the various levels of cleaning required for reusable devices

Design for health

How do we design workplaces to facilitate safe and environmentally healthy sterilization and high-level disinfection? The Joint Commission and other agencies require measurement of and set limits on levels of chemical vapors in the air. The Joint Commission mandates plans and training for chemical spill response, and encourages standardized operations for high-level disinfection and sterilization practices. Industrial hygienists and infection control practitioners should be at the table for design and system development of all areas performing high-level disinfection and sterilization. Of equal importance, though, is reducing the number of areas where liquid or cold sterilants are used.

Separation of clean and dirty

CDC’s Healthcare Infection Control Practices Advisory Committee (HICPAC) published the Guidelines for Environmental Infection Control in Healthcare Facilities in 2001. It is a comprehensive summary of recommendations for the prevention and control of infectious diseases linked to healthcare environments. While it does not specifically call for physically separate clean and dirty utility rooms, it stresses the principle of segregating contaminated and clean equipment and supplies. In addition, the Association for Professionals in Infection Control and Epidemiology, Inc. (APIC) has guidelines for infection prevention and control in flexible endoscopy areas.2 These guidelines recommend that besides separate hand washing and utility sink facilities, work flow should be designed to avoid the commingling of contaminated with clean equipment, and should promote good infection-control practices (figure 2).

After the procedure, the outside of the scope is wiped clean and flushed while still attached to the video tower (1). The scope is removed from the tower and transported to the Scope Wash Room (2), where it is leak tested and manually cleaned with enzymatic cleaner and a brush, then rinsed and the outside dried. The cleaned and dried scope is placed in the automated endoscope reprocessor (3). At the completion of the cycle the scope is flushed with alcohol and dried with compressed air, then removed and stored (4) in a separate location. If functional spaces are not directly adjacent then covered trays or carts should be used to transport scopes between functional rooms

Train for safety

The Occupational Safety and Health Administrations’ Hazard Communication Standard requires documented staff training for those working with any chemical. The standard requires knowledge of the hazards associated with the chemical, proper use, methods of exposure, appropriate personal protective equipment, spill response and access to material safety data sheets. The training should be given whenever anyone is introduced to the material, when and if there is a change of work practices, and annually.


Control of high-level disinfection and sterilization can be established through oversight by an Environment of Care Hazardous Material and Waste Management Committee, as required by the Joint Commission. Policies should be clear and effectively posted. Worker training, appropriate protective equipment, standardization and ongoing documented monitoring are integral to safety, compliance, quality control and staff and environmental safety.

Continuous quality improvement

Taking a closer look at current practices provides an opportunity to standardize practices, improve safety protocols, and the quality of the cleaning process. Safe and effective sterilization and high-level disinfection require oversight, but with controls in place, these practices can balance safety and healing. HD


Erica Stewart, CIH, HEM, is a Project Manager with Kaiser Permanente’s National Environmental, Health and Safety Department. She has worked for Kaiser Permanente in various EH&S capacities for 16 years and worked in private EH&S consulting for seven years before joining Kaiser Permanente. She was the 2006 Chair of the AIHA Stewardship and Sustainability Committee and 2007 Chair of the AIHA Healthcare Working Group.

Janet Brown is Partner Program Manager for Hospitals for a Practice GreenHealth (

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  1. Johnson & Johnson’s Advanced Sterilization Products Cidex OPA Label LC-20390-008 Rev.B (Rev. C or Rev. D)
  2. Alvarado CJ, Reichelderfer M. APIC Guideline for Infection Prevention and Control in Flexible Endoscopy. AJIC, vol 28, number 2, April 2000, p 138-155.