Veterinary Compliance Assistance

Sterilants and Disinfectants in Veterinary Facilities

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.  This section provides an introduction to sterilants and disinfectants in common use, and includes information on proper handling and disposal, and on available alternatives.

The information presented below applies primarily to sterilizing and disinfecting medical devices and other items that may contact humans and animals.

For more information on chemicals used for disinfection in janitorial cleaning and similar applications, see the Cleaning Chemicals page.


Sterilants and disinfectants kill living organisms.  They need that essential property to perform their basic function.  But "desirable" organisms (like us, presumably), and "undesirable" organisms, like disease-causing pathogens, are not that different at the cellular level, publicawhere their basic metabolic processes are concerned.  If a substance is toxic to pathogens, chances are it will also be harmful to other organisms.

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:

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

Veterinary 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 -- in other words, with providing "how clean is clean?" guidelines based on plausible exposure risks.  The other system is concerned with classifying levels of effective potency of disinfection materials.  Using the two systems, you 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 increase your 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 Mycobacterium tuberculosis, 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.)

Choosing the Appropriate Material to 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 noncritical risk situations, low-level disinfectants may be adequate.

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

  • Ethylene oxide (EtO). Clinics typically use ethylene oxide (EtO) to sterilize moisture- and heat-sensitive instruments. EtO is a hazardous air pollutant (HAP) and the operation of EtO sterilizers at human healthcare facilities is regulated by a National Emission Standard for Hazardous Air Pollutants (NESHAP). This regulation does not apply to veterinary hospitals and clinics.
  • 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 (see the following section).  Alternatives are available for most applications (see the Alternatives section below).

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.


(Note -- this discussion deals with the risks involved in using and disposing of the most commonly used sterilants and disinfectants.  The risks associated with infection are surveyed in the previous discussion.)

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 healthcare facilities employees and visitors


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

(Source: Glutaraldehyde: Occupational Hazards in Hospitals, CDC)

Compliance Requirements

Several Occupational Safety and Health Administration (OSHA) regulations relate to sterilants and disinfectants:

  • OSHA has established a permissible exposure limit (PEL) standard for ethylene oxide of 1 ppm in air as an 8 hour time weighted average, and 5 ppm over any 15 minute sampling period.
  • OSHA's Hazard Communication Standard (HazCom), requires that information concerning any associated health or physical hazards be transmitted to employees via comprehensive hazard communication programs (Go to VetCA HazCom page). The programs must include:
    • Written Program.  A written that meets the requirements of the Hazard Communication Standard (HazCom).
    • Labels. In-plant containers of hazardous chemicals must be labeled, tagged, or marked with the identity of the material and appropriate hazard warnings.
    • Safety Data Sheets. Employers must have an SDS for each hazardous chemical which they use and SDSs must be readily accessible to employees when they are in their work areas during their workshifts.
    • Employee Information and Training. Each employee who may be "exposed" to hazardous chemicals when working must be provided information and be trained prior to initial assignment to work with a hazardous chemical, and whenever the hazard changes.
  • Depending on the ingredients contained in a sterilant or disinfectant and its manner of use, employee protection may be required including:
    • Ventilation controls
    • Personal protective equipment
    • Clothing or gloves

and other applicable precautions. This assessment should be made by the employer, again, based on the unique conditions of use of the product at that establishment.

  • Where the eyes or body of any person may be exposed to injurious corrosive materials, employers must provide suitable mechanisms for quick drenching or flushing of the eyes and body within the work area for immediate emergency use [1910.151(c)].

Certain Environmental Protection Agency (EPA) regulations may also apply to sterilants and disinfectants:

  • The Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) provides EPA with the authority to oversee the registration, distribution, sale and use of pesticides.  FIFRA applies to all types of pesticides, including antimicrobials, which includes sterilants, disinfectants and other cleaning compounds that are intended to control microorganisms on surfaces.  FIFRA requires users of products to follow the labeling directions on each product explicitly. (go to FIFRA page).
  • Discarded sterilants and disinfectants may be a hazardous waste due to their corrosiveness, flammability, toxicity, or reactivity.  For information on how to properly identify your hazardous waste, please see VetCA's Hazardous Waste Determination page. You should also check the VetCA Hazardous Waste State Resource Locator page for your state for links to any state-specific variations on the federal rules that may apply to you.

Some sterilants and disinfectants are considered hazardous wastes, and are regulated under RCRA (see below).

A brief summary of which federal agency plays what role in the regulation of sterilants and disinfectants can be found in a document from the Centers for Disease Control.  


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, along with specific references to some commercially available products.

The list is provided for your convenience, and is not intended to provide specific recommendations.  In general, when selecting an alternative, you should choose a disinfectant that is sufficiently effective, but is the least toxic to employees and the environment.

Here are 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 the FDA 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. 

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
  • 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 several companies.

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. 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 (RCRA).  You should also to check to see if the end product being used (i.e. the product after dilution) also needs to be managed under RCRA.

Here are a few considerations:

  • If the sole active ingredient of a sterilant or disinfectant is a P or U-listed waste, the product itself must be managed as a hazardous waste.  (This information should be available on the Safety Data Sheet [SDS, formally Material Safety Data Sheet (MSDS)] that your supplier can provide for the product.)
  • A sterilant or disinfectant might also have to be considered a characteristic hazardous waste due to:
    • Corrosivity: It is important to check the pH level of the product. Many products have pHs higher than 11 or lower than 2. A sterilant or disinfectant product may be considered hazardous if it has a pH of less than 2 or greater than 12.5. This information can be determined form the MSDS under the "Physical Data" category.
    • Toxicity
    • Reactivity
    • Ignitability

See the Hazardous Waste Determination page for more background information on this topic.

Some solutions can be disposed of to the sanitary sewer if the local POTW permits it.  You are strongly advised to check with your 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.  (Source: Replacing Ethylene Oxide and Glutaraldehyde, USEPA)

More Resources

General Information

EPA Office of Pesticide Programs, Chemical Search. Enter chemical name or CAS number to find registration and chemical information. Also, provides EPA point of contact. A video tutorial is available.

Fact sheets on EtO and glutaraldehyde are also available from OSHA. 

The EPA provides a list of antimicrobial agents registered as pesticides.

Best Management Practices

Best Practices for the Safe Use of Glutaraldehyde - extensive best practices recommendations from the federal Occupational Safety and Health Administration (OSHA)

Glutaraldehyde: Occupational Hazards in Hospitals -  provides useful information on adverse health effects of glutaraldehyde and on how you can be exposed to glutaraldehyde, and suggests control methods and work practices to prevent or reduce your exposure to glutaraldehyde.  The brochure was published by the National Institute for Occupational Safety and Health (NIOSH), a division of the Centers for Disease Control.


Replacing Ethylene Oxide and Glutaraldehyde - fact sheet from the EPA series of environmental best practices for healthcare facilities.  It provides a concise summary of alternatives to EtO and Glutaraldehyde. Center for Devices and Radiological Health (2000).


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