Proper Use of Disinfectants in Laboratory Settings

February 24, 2017 | cleancore | Filed Under: Industry Articles, Trade Magazine stories, Uncategorized

Aqueous Ozone cleaning

A cleaning professional working in a laboratory was tasked with disinfecting work surfaces in the lab.  The disinfectant he was using had already been pre-mixed and poured into a bucket.  His job was to take a microfiber cleaning cloth and wipe down the surfaces with the water/disinfectant solution.

Following up on his work, his supervisor then tested the surfaces using what is called an ATP monitoring system. Already in use in many laboratories for a variety of functions, when it comes to cleaning these tools are used to determine how much adenosine triphosphate (ATP) is found on a surface before or after cleaning.

While ATP on a surface does not indicate specifically that harmful pathogens are present, in professional cleaning it is used as a barometer.  Too high a reading indicates there is reason for concern that the surface was not adequately cleaned or needs to be cleaned to protect human health.

The supervisor became alarmed because the ATP monitor readings were surprisingly high, far exceeding what he expected.  Further, knowing the cleaning worker started working from the front of the laboratory moving to the back, he found that as the surfaces were tested for ATP, the readings continued to increase.

It was later determined that the cleaning worker was following proper protocol as he had been trained.  So why were the ATP readings so high?  There are several reasons this could – and often does – happen when working with disinfectants, but the three primary reasons are:

• The areas where the disinfectant was applied had not been cleaned before the disinfectant was applied
• The cleaning cloth used had become soiled, causing it to spread contaminants instead of remove them
• What is termed “quat binding” had occurred, impacting the effectiveness of the disinfectant.
To better understand what is happening and why the surfaces were left with high ATP readings, we need to explore all three of these issues in greater detail.

The Disinfectant Two (plus) Step

The first thing administrators should know about the proper use of disinfectants is that surfaces must be cleaned first before the disinfectant is applied.  This means that if there is dust or debris on a surface, it must be removed.  Then the surface should be cleaned using a pH neutral cleaning solution.
Cleaning physically removes soils from a surface. The cleaning solution helps dissolve and loosen soils and the physical wiping using the cloth provides the necessary agitation to lift and remove them from the surface. This also helps ensure soils and pathogens are not embedded in a surface, making it hard for the disinfectant to reach them.

Disinfecting, on the other hand, kills most all pathogens on a surface, helping to eliminate their potential harm to human health.  According to the Centers for Disease Control and Prevention, while disinfectants help destroy or inactivate germs and prevent them from growing, “[they]have no effect on dirt, soil, or dust.”

Without physically removing the soils on a surface, the efficacy of the disinfectant will be diminished. Depending on the setting, some cleaning experts suggest that a surface be rinsed after cleaning and before the disinfectant is applied.  The rinsing helps remove any remaining soils that may be present plus it can help remove chemical residue from the surface.

Contaminated Cleaning Cloths

In 1971, a study was published in the journal Applied Microbiology1 investigating the spread of bacterial contamination in a hospital. “It was found that mops [used to clean the floors in the hospital], “stored wet, supported bacterial growth to very high levels and could not be adequately decontaminated by chemical disinfection.”
The study found that as they became soiled, the mops became contaminated and spreading germs and bacteria instead of removing them.  And because people generally have an estimated 50 direct and indirect contacts with floors each day, the germs and bacteria were transferred from the floor to someone’s hands and from there to surfaces, causing cross contamination.2

We now know the same thing can happen with cleaning cloths. As the cloth becomes soiled, it can begin to spread pathogens from one surface to another.  The soil also weakens the efficacy of the disinfectant because the disinfectant is now working to eliminate germs and bacteria on the cleaning cloth first and on surfaces secondarily.

Again, according to healthcare specialists Joe Saunders and Lynda Mathiesen, “as the employee mops a floor and immerses the [soiled] mop into the bucket of disinfectant solution, the solution will degrade. At a certain point…a disinfectant will be rendered ineffective.”3  Soiled cleaning cloths would have the same effect on a disinfectant solution.

Disinfectants Losing Steam

One of the reasons a disinfectant can lose its bacteria and germ killing punch is because as the disinfectant is used, quats (quaternary ammonium chloride)—the active ingredients in the disinfectant—are absorbed into the wipes, cleaning cloths, and mop heads.  Quats have positively charged ions, and these cleaning applicators typically have negatively charged ions.
The end result is that as the cleaning cloth is used, the killing power of the disinfectant is diminished.  When you realize it is also getting more soiled in the cleaning process, you see how this can reduce the effectiveness of the disinfectant dramatically. The result: pathogens remain on the surface which is why, along with the other items discussed, our ATP readings are so high and get worse as cleaning tasks are performed.

Addressing these Challenges

There are certainly other issues that can impact the effectiveness of a disinfectant and we have listed these in the sidebar below.  But since the three discussed here are vital to effective disinfecting, let’s discuss how these challenges can be addressed:

The Two (Plus) Step

All surfaces must be cleaned first using a pH neutral cleaner before disinfecting.  This is key and the more effectively it is performed, the more likely harmful pathogens will be removed and/or eliminated by the disinfectant.  An option being used in food service and professional cleaning is to use aqueous ozone for this task.  Aqueous ozone has been used for years to “treat” drinking water and clean carpets and hard surfaces, often more effectively than a traditional cleaning solution.  (See Sidebar: Making Aqueous Ozone)

Contaminated Cleaning Cloths

Cleaning cloths should be changed frequently, possibly as soon as one surface is cleaned and before cleaning the next, depending on the setting. Also, establishing a color-coded cleaning system will help ensure, for instance, a restroom cleaning cloth is never used to clean and disinfect a laboratory surface.

Quat Binding

Addressing this challenge can be more perplexing.  Ensuring surfaces are cleaned as effectively as possible before disinfecting helps to minimize the problem. Other steps to take include the following:

• Spray the disinfectant directly on the surface to be cleaned, not on the cleaning cloth
• Do not pour a disinfectant into a bucket of water or store cleaning cloths in the bucket
• Consider alternatives to traditional disinfectants such as bleach (be wary of environmental issues) or use an aqueous ozone cleaning system; quat binding cannot take place with these alternatives
• Look for disinfectant that do not contain “quats.”

Many people do not realize that disinfectants are almost as important to human health as was the development of penicillin or other so-called “miracle drugs.”  We’ve known about contamination issues for thousands of years.  All the way back in the first century BC, the ancient Roman scholar Marcus Terentius Varro wrote, “there perhaps exist, in marshy places, animals which are invisibly small, and which cause serious diseases by invading the body.”

Now we know how to eliminate these “animals,” which we now call microorganisms or pathogens.  We can do it as long as the disinfectants we use are used properly.

Matt Montag is national sales manager for CleanCore® Technologies, manufacturers of aqueous ozone cleaning systems designed for the professional cleaning industry.

1 “Hospital sanitation: the massive bacterial contamination of the wet mop,” by researchers J. C. N. Westwood, M. A. Mitchell, and S. Legacé, Applied Microbiology, April 21, 1971.
2 Indirect floor contact includes such things as tying shoelaces that have dragged on the floor; leaving a purse on a restroom floor and then picking it up from the surface touching the floor, etc.
3 “Floor Disinfection: Creating a Healthier Environment,” by Joe Saunders and Lynda Mathiesen, published in Infection Control Today, June 1, 2000.
Also, Westwood, J. C. N., Mitchell, M. A., & Legacé, S. (1971). Hospital Sanitation: The Massive Bacterial Contamination of the Wet Mop. Applied Microbiology, 21(4), 693–697.
[reference:, under the heading Formats,citation]

Sidebar: Making Aqueous Ozone

Ozone can be made mechanically through the interaction of electricity and oxygen.  It is then infused into water to create aqueous ozone. Once applied to a surface, it eventually changes back into water and oxygen.