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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.
Properties
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.
Risks
(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.
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, 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.
Alternatives
Replacing
Ethylene Oxide and Glutaraldehyde - EPA fact sheet.
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