Infection Control Today - 08/2001: Think Safety When Choosing the Proper Disinfectant or Sterilant

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Think Safety When Choosing the Proper Disinfectant or Sterilant

By Bill Feil


Scanning electron micrograph magnified 30 times depicting corrosion of stainless steel by chlorine bleach.

Disinfecting or sterilizing environmental surfaces or equipment is not the most glamorous task that one performs in his or her typical workday. It is, however, critical to proper infection control in the acute care and alternate care settings. The selection of which germicidal product to use may not always be obvious. If you were to look carefully at the products in your facility, you may find 5-10 products that are registered as either disinfectants or sterilants. How do you know which product to use? The answer is simple: think safety.

Safety in this setting has many meanings: safety or assurance that the product selected will provide the efficacy required to disinfect or sterilize the surface to be decontaminated; safety for the person using the antimicrobial product; safety for the surface which is being treated; safety for others being exposed to that and other surfaces; and finally, safety for the environment. Every time someone uses a disinfectant product, they are knowingly or unknowingly making decisions in each of these areas.

Assurance of product efficacy

The first safety decision is safety, or assurance that the product selected will provide the proper efficacy. This is not a new topic in the infection control arena. In fact, most of today's guidelines still reference a process outlined in 1968 by Spaulding.1 In his process, he divided items requiring disinfecting or sterilizing into three categories: critical, semicritical, and noncritical. Each category has its own recommendations for the degree of decontamination that would be necessary. This process has continued to evolve with time and many very useful guidelines have already been written and are periodically updated. These include:

  • The Centers for Disease Control and Prevention (CDC) published their revised document, "Guideline for Handwashing and Hospital Environmental Control, 1985."2
  • In 1996, Rutula revised the "APIC Guidelines for Infection Control Practice."3
  • In 2001, Favero and Bond authored a chapter "Chemical Disinfection of Medical and Surgical Materials."4

Figure 2. Stereo microscope images of plastic magnified 75 times. Side A is the unexposed surface. Side B is after exposure to the chemical.

These guidelines provide very detailed strategies to ensure that the selection of a disinfectant or sterilant is appropriate for the risk associated with a particular surface or instrument.

The guidelines above2,3,4 help you determine the class of product required to properly decontaminate the surface. Using this knowledge base, healthcare workers must then select a product that meets these requirements. The only way to do this is by thoroughly reading the product labels. There is a wealth of information on the label. Both the Environmental Protection Agency (EPA) and the Food and Drug Administration (FDA) review and approve product labels. This is to ensure that the information required to make proper product selection is contained on the label. The label also indicates the proper uses of the product, including the sites of application (bathrooms, floors, etc.) as well as dilution instructions. At first glance these may seem confusing, but if you understand what each section provides, the label will provide the information required to make the proper decision. Periodically there are articles written to help understand label content and regulations,5 but if you are in doubt, contact the chemical manufacturer and get the answers needed to make the correct decision.

Once you have selected the product, it must be used properly. Although this seems obvious, it is often overlooked. Chemical manufacturers are required to generate data to substantiate all label claims. If the product is used incorrectly, there is no assurance that you have performed the job you intended. There are several critical steps in using a disinfectant or sterilant. For concentrated products, the first is the dilution. What does 1/2 ounce/gallon look like in a mop bucket? In a spray bottle? The free pouring of germicides is a recipe for disaster. If you are going to use a dilutable product, use the dispenser provided by the chemical manufacturer. If you disagree, do a simple test. Take one of the products in your area and find a graduated cup, beaker, or other reservoir and ask 5-10 of your associates to pour out one ounce. For most products, one ounce is about 30 mL. You will be surprised at the results. Remember, a dispenser doesn't have to be a piece of equipment on the wall. There are many unit-dose products available which are essentially simplified dispensers.

Using chemical dispensers also is not foolproof. Dispensers require routine maintenance. Most dispensers have metering tips that may become partially obstructed or even plugged over time. This will vary greatly depending on the water conditions in your area of the country. You need to verify that your dispenser is working properly. In addition to proper dilution, you need to ensure that the proper quality of water is being used. Again, the product label details the quality of water that can be used to dilute the product. Using the incorrect water source can and will affect the efficacy of the product. Not only should it be of the proper water hardness, but it should be routinely monitored for non-coliform bacteria.6

Ready-to-use germicides are always an option. For these products, the manufacturer ensures that the product has been properly prepared and is ready to be delivered to the surface. There is a cost for this convenience, but in many cases it does have a place in the surface decontamination strategy.

Once you have diluted the product correctly, you must determine whether the surface needs to be pre-cleaned. Many products are registered as one-step cleaner/disinfectants. This claim is intended for situations with low soiling. The laboratory test is typically performed using a 5% soil challenge. The general rule of thumb is, if it looks dirty, it should be pre-cleaned first. Applying the disinfectant in two separate applications can accomplish this. If the product does not have the one-step cleaner/disinfectant claim, you should always pre-clean, even if the surface appears clean.

The last step in a disinfection process is the actual application and the time required to perform the task adequately. Testing of germicides is always concentration and time dependent. Most germicides require a 10-minute contact time to disinfect a surface. This is based on the testing methodology required by the EPA. Products are beginning to be registered with shorter contact times, but the majority of the products still carry the 10-minute contact time. If you shorten the contact time from what is stated on the label, you may compromise the efficacy of the product. Take the time to do it correctly. For products that are sprayed on the surface, make sure you use the proper number of sprays to thoroughly wet the surface. If you don't, you may not be applying sufficient germicide to provide the efficacy stated on the label.

Safety for the person applying the chemical

The second safety decision is for the person who is applying the chemical to the surface. There are two aspects to this discussion: safety from the chemical and safety from the microbes. Proper safety equipment for use of the chemical germicide can be found in two locations: the product label and the product MSDS. A germicide's function is to kill microbes on surfaces. There are many vulnerable surfaces on the human body and these should be protected properly. Chemical manufacturers are required to test products to determine what precautions will be necessary to keep users properly protected. These tests categorize sensitivities to the skin, eyes, mucous membranes, etc. The proper personal protective equipment (PPE) is spelled out and should be used. This is easy to dictate administratively, but it will require surveillance to ensure that it is being implemented properly.

In addition to PPE, the label, and MSDS also provide instructions in the event of accidental exposure to the chemicals. You should have your product MSDSs accessible. This will save time in determining the proper course of action and will also give instructions so further damage is not done through improper treatment after the accident has occurred. Finally, the MSDS also contains emergency numbers that can be called for further consultation.

Chemical exposure is not the only concern, however. There have been several articles published that further articulate the need for use of proper PPEs.7,8,9 These outline the transfer of microorganisms from the contaminated surface to fingertips, gloves, uniforms, other surfaces, and other patients. The use of PPE and proper handwashing protocols can be key elements to stopping the spread of many organisms. The benefit of preventing nosocomial infections is worth the cost of the PPE and time to perform proper handwashing after decontaminating surfaces. This ensures that you are working in a safe environment and that others are also not being unnecessarily exposed due to cross contamination.8

Safety for surfaces

The third safety decision is for the surfaces to be disinfected. Improper use of chemicals can and will cause damage to surfaces. Household bleach has been recommended for many applications, however, bleaches can be corrosive to metal surfaces. Figure 1 depicts the corrosion of stainless steel by chlorine bleach. This damage is not reversible and can be costly.

Resilient floor tiles are another excellent example of surfaces that can be easily damaged. Floor finishes are sensitive to the pH of the products used to clean them. At the low pHs of some acid bathroom cleaner/disinfectants (< 2.5), the floor finish will be stripped off the floor. This can also occur at high pHs (> 10). Some quaternary surfactant based disinfectants can have pHs in this range.

Plastics can also be damaged. Figure 2 shows chemical damage to a plastic. Although plastics are generally resistant to chemical exposure (chemical products are stored in plastic containers), this is not a guarantee that it is safe for all types of plastic. Many different resin chemistries are utilized in the acute care and alternate care settings and certain chemicals may not be safe on all plastics. If in doubt, ask the manufacturer of either the chemical or the surface, or place a small amount of product on the surface and look for damage.

A final concern for surface safety is the application procedure. Many surfaces are laminated or coated with chemical-resistant materials. The use of mechanical action can remove the protective coating and expose the non-resistant portion of the surface to the germicide. Figure 3 shows where the protective coating on a shower flange was etched away with a scouring pad. This allowed the acid bathroom cleaner to attack the underlying metal. This can be true for other surfaces as well. Mechanical damage and chemical damage can at times be difficult to distinguish, but the end result is the same--the surface is irreversibly damaged.

Safety for the environment


Figure 3. Stereo microscope images of plastic magnified 75 times. Side A is the unexposed surface. Side B is after exposure to the chemical.

The last safety decision is for the environment. This responsibility again falls primarily on the chemical manufacturers and their suppliers. The EPA or FDA must approve each ingredient in a germicidal formulation for use. There are two registration pathways, one for active ingredients (antimicrobials) and one for inert ingredients. There are many tests required to ensure that these materials are safe for the environment. Registering a new active or inert ingredient can take several years and millions of dollars. This only ensures that, if properly used, the germicide will provide the level of safety to the environment that the government agencies require. You need to ensure that they are used properly and that they are disposed of properly. We all need to do our part to minimize the impact on the environment.

Ensuring appropriate selection and safe use of disinfectants and sterilants

How do you ensure that you and others are selecting the proper disinfectant? Education and training are the only ways to accomplish this task. There are three keys to any education and training program:

  • Education materials: Have a list of references available for new hires. This can be through the distribution of hardcopies of literature, by distributing a list of Internet sites that contain the information, by showing the location of the MSDS, and other relevant information and by having wall charts next to your germicides depicting proper use.
  • Training: Take the time to train every staff member on proper use of germicides. Training can be in many forms: manufacturer's programs, continuing education courses, e-learning, and manufacturer provided in-service training programs. In addition to these programs, make use of local, regional, and national meetings as a means to provide training. These can be expensive, but if you utilize the "train the trainer" approach, these meetings can be extremely beneficial.
  • Surveillance: For a program to work effectively, there must be follow-up with routine surveillance programs for the users, equipment, water quality, etc. Each organization needs to identify the persons responsible, provide the necessary resources and develop a corrective action program that encourages prompt response to potential issues without threatening individuals. Praising identification of issues, rather than focusing on assessing blame will encourage everyone to get involved. Encouraging the use of test kits and/or test strips, having a suggestion box or fix it list and providing constant feedback will keep the focus on doing the job safely and correctly.

In the end, proper selection and safe use of disinfectants and sterilants is a group and individual responsibility. By choosing a particular disinfectant or sterilant, you are making many decisions. Take that responsibility seriously. Educate yourself, obtain the proper training, and most importantly, think safety.

William Feil is a scientist for the Professional Products Division of Ecolab Inc. in Mendota Heights, Minn.

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