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Sterilants & Disinfectants

In a healthcare setting, it is essential to be able to control infectious organisms. Sterilants and disinfectants are important tools for meeting that need. But because they are necessarily toxic to living organisms, sterilants and disinfectants must be handled carefully, and their associated wastes must be managed properly to avoid causing unintentional harm as they fulfill their intended function.

The information presented below applies primarily to sterilizing and disinfecting medical devices and other items that may contact patients. For more information on chemicals used for disinfection in janitorial cleaning and similar applications, see the Green Cleaning pages.

While all sterilants and disinfectants are toxic to some degree, some have greater killing power than others. High toxicity is an advantage in critical applications, where the risk of infection must be reduced to the lowest possible level. But the greater effectiveness of highly toxic materials comes at a price:

  • the risk of harm to staff and patients through inadvertent exposure will be greater
  • the disposal of wastes from disinfection processes may become more difficult and costly

Healthcare professionals have developed two interrelated classification systems to help determine appropriate infection control materials for various clinical situations. One system is concerned with classifying levels of infection risk guidelines based on plausible exposure risks. The other system is concerned with classifying levels of effective potency of disinfection materials. Using the two systems, an organization can match the material with the need, and ensure a safe level of infection control without overkill – i.e. without overusing materials that pose needless risks of their own, and increasing costs as well.

Categories of Infection Risk

According to one commonly used scheme, infection risk situations are divided into three categories:

  • Critical contact directly with internal fluids, such as with circulating blood though blood vessel walls, or contact directly with tissues through broken skin
  • Semi-critical: contact with mucous membranes, or contact with broken skin
  • Noncritical: contact with intact skin

Categories of Effective Potency

Sterilants and disinfectants are distinguished according to the degree to which they can be expected to destroy the organisms they contact:

  • Sterilants are capable of completely eliminating or destroying of all forms of microbial life, including spores.
  • Disinfectants form a less absolute category—they will destroy some, but not necessarily all organisms. The category is further divided into subcategories, as follows:
    • High-level disinfectants – destroy all microorganisms, with the exception of high numbers of bacterial spores.
    • Intermediate-level disinfectants – inactivate even resistant organisms such as Mycobacteriumtuberculosis, as well as vegetative bacteria, most viruses, and most fungi, but do not necessarily kill bacterial spores.
    • Low-level disinfectants – kill most bacteria, some viruses, and some fungi, but cannot be relied on to kill resistant microorganisms such as tubercle bacilli or bacterial spores.

             (Source: APIC.)

Match Risk with Potency

  • Any objects or materials used where the risk of infection is critical should be absolutely sterile.
  • For semi-critical risk situations, either a high-level or a medium-level disinfectant may be appropriate, depending on the type of exposure. For example, a publication from the Association for Professionals in Infection Control and Epidemiology (APIC) recommends high-level disinfectants for devices like laryngoscopes and endoscopes that are inserted deep into body cavities, and medium-level disinfectants for less intrusive devices such as oral or rectal thermometers.
  • For non-critical risk situations, low-level disinfectants may be adequate.

The most widely used sterilants and disinfectants in healthcare facilities are:

  • Ethylene oxide (EtO): Hospitals typically use ethylene oxide (EtO) to sterilize moisture- and heat-sensitive instruments.
  • Glutaraldehyde: Glutaraldehyde is a high-level disinfectant most frequently used as a disinfectant for heat-sensitive equipment such as dialysis instruments, surgical instruments, suction bottles, bronchoscopes, endoscopes, and ear, nose, and throat instruments. Glutaraldehyde is also used as a tissue fixative in histology and pathology laboratories and as a hardening agent in the development of x-rays. Glutaraldehyde            products are marketed under a variety of brand names and are available in a variety of concentrations (solutions range in concentration from 2.4 – 3.4%), with and without surfactants.

Both of these materials have been found to cause potential problems for facility staff and for any other individuals who may be exposed to them. Alternatives are available for most applications. Note that there are also non-chemical methods of sterilizing and disinfecting that may be suitable in some cases:

  • Some methods rely on high heat and pressure, such as the conditions obtainable in an autoclave. Since boiling in water is not sufficient for sterilization—some particularly hardy spores can survive exposure to the temperature at which water boils under normal atmospheric pressure—more drastic conditions are needed to sterilize without the use of biotoxic chemicals. Autoclaves are enclosed chambers that operate under increased pressure, allowing water to remain liquid at temperatures well above its normal boiling point. This can provide a very effective sterilization environment. However, autoclaving is not an option for heat sensitive equipment.
  • Radiation can also be used for sterilizing and disinfecting, but considering its own well-known suite of problems, it would not generally be considered a preferable alternative to chemical methods from an environmental and safety standpoint.

Risks to Human Health

Ethylene oxide (EtO) poses several health hazards requiring special handling and disposal of the chemical, and training in its use. It is identified by the National Toxicology Program as a known human carcinogen and has several other acute and chronic health effects. Ethylene oxide:

  • can cause nausea, vomiting, and neurological disorders
  • in solution, can severely irritate and burn the skin, eyes, and lungs
  • acts as a probable teratogen, and may pose reproductive hazards
  • may damage the central nervous system, liver, and kidneys, or cause cataracts
  • is extremely reactive and flammable, increasing the risk of chemical accidents that could injure hospital employees and patients

(Source:  USEPA)

Glutaraldehyde is not a human carcinogen. However, several health effects have been reported among healthcare workers exposed to glutaraldehyde:

  • asthma, and breathing difficulties
  • burning eyes and conjunctivitis
  • headaches
  • nosebleed, irritation, sneezing, and wheezing
  • hives
  • nausea
  • rashes and allergic dermatitis
  • staining of the hands
  • throat and lung irritation

For more information on environmental compliance obligations relative to sterilants and disinfectants, check out EPA's Healthcare Environmental Resource Center.

Alternatives

Because of the health and environmental hazards associated with glutaraldehyde and ethylene oxide, various alternatives have been investigated. This section lists several sterilants and high level disinfectants that have been cleared by the Food and Drug Administration (FDA) for processing reusable medical and dental devices (click here for updated FDA information), along with specific references to some commercially available products.

The list is provided for convenience, and is not intended to provide specific recommendations. In general, when selecting an alternative, organizations should work with Infection Prevention &  Control to select a disinfectant that is sufficiently effective, but is the least toxic to employees and the environment.

A few general observations:

  • Disinfectants that act by generating active forms of oxygen, such as hydrogen peroxide or peracetic acid, typically create fewer by-products than compounds relying on other active elements, such as chlorine or the form of nitrogen found in quaternary amine compounds. This means fewer toxins finding their way to the sewer.
  • Hydrogen peroxide and peracetic acid are less easily inactivated by other, noninfectious organic matter than some of the non-oxygen disinfectants.
  • Hydrogen peroxide and peracetic acid can be effective against a broader range of infectious agents than some of the other alternatives.

Under any circumstances, when alternatives sterilants and disinfectants are to be used on a medical device, you should check with the original equipment manufacturer for any specific warranty restrictions on the use of specific materials or methods of disinfection.

  • Hydrogen peroxide provides high level disinfection in 30 minutes at 20 degrees Celsius. Although theFDA has approved products containing 7.5% hydrogen peroxide as a high-level disinfectant/sterilant, it has not been found to be compatible with all flexible gastrointestinal endoscopes (e.g., Olympus, Pentax or Fujinon).
  • Peracetic acid is part of the family of peryoxygen compounds. A concentration of 0.2% peracetic acid is rapidly active against all microorganisms including bacterial spores, and is effective in the presence of organic matter. It has proved to be an acceptable alternative to EtO.

However, you should note that in some instances, manufacturers have not yet approved the use of EtO alternatives for sterilization of their products. Such limitations vary by vendor and are not specific to one instrument or medical device product type. For example, one typical hospital has investigated EtO alternatives, but still requires the use of EtO on the following five instruments: angioscopes, choledocoscopes, surgiscopes, bone flaps and     hysterectoscopes.

(Source: Replacing Ethylene Oxide and Glutaraldehyde, USEPA).

  • Peracetic Acid-Hydrogen Peroxide mixtures: Although the FDA has approved products containing 0.08% Peracetic Acid/1% Hydrogen Peroxide as a high-level disinfectant/sterilant, it has not been found to be compatible with flexible gastrointestinal endoscopes manufactured by Olympus, Pentax or Fujinon.
  • Hypochlorite has FDA clearance for high level disinfection in 10 minutes at 25 degrees Celsius.

Ortho-phthalaldehyde (OPA) is chemically related to glutaraldehyde. According to the Michigan Health and Hospital Association (MHA), the disinfecting mechanism of OPA is thought to be similar to glutaraldehyde and is based on the powerful binding of the aldehyde to the outer cell wall of contaminant organisms. A notable difference between the two commercial disinfectants is the percent of active ingredient in each product. Commercial OPA-based disinfecting products contain only 0.55% of the active ingredient, while most glutaraldehyde-based disinfecting products contain 2.4 to 3.2% active ingredient – 5 to 7 times that of OPA products. OPA is a widely used glutaraldehyde alternative. Its potential benefits include:

  • lower inhalation exposure risk,
  • reduced disinfecting time (12 minutes vs. APIC-approved 20 minute disinfection time and FDA-approved 45 minute disinfecting time for Cidex),
  • solution is approved for use in almost all of their equipment without negating the warranty, and
  • cost is significantly less than installing a more substantial ventilation system to minimize respiratory irritation from using glutaraldehyde.

Ortho-phthalaldehyde is a clear blue solution with little odor. It is a potential irritant of eyes, skin, nose and other tissues resulting in symptoms such as stinging, excessive tearing, coughing and sneezing. It is a potential skin and respiratory sensitizer that may cause dermatitis with prolonged or repeated contact and may aggravate pre-existing bronchitis or asthma. In addition, the product stains proteins on surfaces to gray/black. Although OPA may pose similar occupational hazards to glutaraldehyde, the risk is significantly reduced due to the low percentage of OPA and relatively low vapor pressure of OPA-based commercial products. OPA does not currently have a recommended exposure limit; however, vendors recommend that similar protective equipment be used, including gloves and goggles.

(Source: Replacing Ethylene Oxide and Glutaraldehyde, USEPA).

Disposal of Sterilant and Disinfectant Wastes

Unused disinfectant concentrates may be considered hazardous wastes in some cases.  If so, they need to be managed under a particular set of rules.  The used end product being used (i.e. the product after dilution) may also needs to be managed under RCRA. Some solutions can be disposed of to the sanitary sewer if the local POTW permits it. Healthcare organizations are strongly advised to check with their POTW to determine what wastewater discharges of sterilants and disinfectants are acceptable.

A note on the disposal of ortho-phthalaldehyde (OPA)-containing products: Due to its toxicity, California legislation deemed Cidex OPA a hazardous waste beginning January 1, 2001. However, this legislation exempts healthcare facilities from tiered permitting regulatory requirements when treating Cidex OPA with Glycine on site to render it a non hazardous waste. Note also that if local publicly owned treatment works (POTWs) or sewer agencies have other prohibitions against sewerage of aldehydes, facilities must seek approval for this process as well.

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