Different solutions for different purposes
You may be familiar with cleaning, but what about sanitizing and disinfecting? Here are some basic definitions so we all have the same understanding:
- Cleaning – the process of removing unwanted substances, such as dirt, microbes, and other contaminants from an object or surface. It can be done dry or with a solution.
- Sanitizing – ridding a surface of contaminants that could affect your health. Sanitizing is meant to reduce the quantity and growth of bacteria, viruses and fungi on a surface and is typically done on food preparation surfaces.
- Disinfecting – when we “kill” the microscopic organisms (as claimed on the label of a disinfectant product) thereby reducing the risk of spreading infection. Cleaning should precede disinfecting.
- Hand Sanitizers – these are not approved by EPA and are not registered disinfectants, so be aware of claims and what’s in them! Alcohols (60% min.) and soaps (surfactants) are good, especially for efficacy against Covid-19. They can be effective at reducing the number of microbes on your hands, but do not remove them as you would when washing with soap and water.
- Alcohols – there are two predominant types of alcohol used to sanitize. Isopropyl alcohol (IPA) and Ethyl alcohol (ETOH or ethanol). They are seldom registered as disinfectants as they evaporate too fast, but are effective against many organisms. They need to be blended with water to make them most effective, typically to a level of 70% alcohol. Read the label for alcohol type and blend.
- Disinfectants – Disinfectants are antimicrobial agents designed to inactivate or destroy microorganisms on inert surfaces. Disinfectants work by destroying the cell wall of microbes, or interfering with their metabolism. They are rigorously tested and approved (certified) by the EPA for the claims made on the product label. Key is what it’s effective against (what types of bacteria, viruses and fungi) and how long it takes (dwell time) to kill them to achieve a 6-Log reduction (99.9999%). Each type of disinfectant has its own advantages and disadvantages.
What’s needed to effectively clean and disinfect against Covid-19?
The good news about Covid-19 is that it is an enveloped virus and therefore easier to kill. It has an outer layer of fatty-acid lipid proteins that it uses to reproduce. This outer envelope can be removed with soap and water, or alcohol - that is why you have heard so much about washing your hands with soap and water or using alcohol-based hand sanitizers!
There have been several studies looking at how long the virus responsible for Covid-19 remains viable on a surface. It could be detected in aerosols up to 3 hours after aerosolization (hence distancing and masks), up to 4 hours on copper, up to 24 hours on cardboard, and 2-3 days on plastic and stainless steel. Higher temperatures and exposure to sunlight will reduce these times, however lower temperatures can lengthen the viability times.1,2 This is longer than most other common viruses and why its important that proper cleaning is done on a routine basis.
So, what about other surfaces, like metals, wood, painted surfaces or fabrics? Do I use soap and water which is effective at cleaning Covid-19 from your hands? It’s certainly a possibility, but there are a few factors worth considering: the types of materials that need to be cleaned, the environments that are being cleaned, and how much time you have to clean a surface. If you are cleaning a whole room or facility, it is not practical to sing the “Birthday” song twice for every surface that you are wiping. That is why there are many other chemicals and disinfectants available.
Let’s look at some of the simple solutions, leading up to the more commercially available disinfectant products:
Soap and water: If mixing a solution, make sure you use enough soap (use at least one-part liquid soap to 100 parts water). It needs to be left on a surface (dwell time) for several minutes to be effective. Recommend 5 minutes minimum to be safe.
Another common household item is malt vinegar – It has been shown that 10% malt vinegar is effective at disinfecting surfaces. Note that white vinegar is not effective.3,4
Alcohol: The two types of alcohol, IPA and ethanol both work equally well against Covid-19. They must be in the 60-80% concentration range to be effective against lipid viruses such as coronaviruses. They work by denaturing the proteins of microorganisms. EPA testing shows that alcohol needs a 5-minute dwell time. Other studies have shown 70% ethanol to be effective against human coronavirus in 1 minute.5,6 The benefit of alcohol is that it evaporates quickly and leaves no residue. That is also its weakness, limiting how and where it can be used. Also, be aware of its flammability.
Bleach: Chlorine is a good disinfectant, has good anti-microbial activities against bacteria, fungi and viruses, and is effective against Covid-19. It must have a minimum concentration of 1000 ppm to be effective. The EPA requires a 2 minute dwell time. The CDC has shown that its effective against coronavirus in 1 minute.5,6 That means taking household bleach (~6% concentration) and diluting it as follows:
- 4 teaspoons bleach per quart of cold water or
- 5 tablespoons (1/3 cup) bleach per gallon of cold water
Bleach does have it drawbacks. You will need to wear gloves as it dries out your skin quickly. It can irritate your nose and throat (wear a mask if it affects you). It can discolor fabrics and damage surfaces (even metals like stainless steel). It degrades over time and is highly reactive with other chemistries: DO NOT mix with vinegar, ammonia or IPA as highly toxic gasses are formed.
Hydrogen Peroxide (HP): HP is used widely in household products due to its oxidizing properties. Commercially available 3% hydrogen peroxide is effective for disinfecting a wide variety of surfaces. It is capable of inactivating bacteria, viruses, spores, yeast and fungi. The EPA requires a 5-minute dwell time.5 It is generally considered safe, as it breaks down into oxygen and water. It does degrade and become less effective over time, so been mindful of the products expiration date on the bottle!
Accelerated Hydrogen Peroxide (AHP) – AHP is a commercially available disinfectant that works much faster than standard AHP. The additives improve its ability to kill more types of microorganisms in 1 minute.3,5 This product is highly recommended as its nontoxic, very effective, and has one of the lowest dwell times in the market. This product is noted to illustrate that commercially available disinfectants can have beneficial properties, such as: safety, faster acting and greater efficacy. There are many other types of disinfectants available. Check out the EPA’s “List N” which details recommended disinfectants effective against Covid-19 here.5
A key item to re-emphasize is the importance of dwell time. Each chemistry has a necessary dwell time for it to kill the relevant microorganism. This is where the surface must remain visibly wet for that period of time. Known dwell times with the above noted products are included herein.
Different types of cleaning
It’s easy to imagine why one needs to clean. People sneeze or cough, propelling virus laden respiratory droplets onto the myriad surrounding surfaces, after which contaminated hands touch many additional surfaces. When we then touch those surfaces, we pick up the virus on us, and then potentially pass on to others as we touch other surfaces ourselves.
There are many ways to clean, some more effective than others. The main objective here is to remove the virus from the surface and inactivate or kill the remaining germs and viruses. There are several key components of cleaning, let’s use the hand washing example with which we are most familiar: rubbing your hands together to cover all the surfaces – providing the mechanical action; using soap and water or alcohol hand sanitizer – using chemistry and removal, and finally the time factor - giving it the proper time to let the soap and water damage the outer layer of the virus. The same holds true for proper cleaning; the key components are the same.
Let’s start with the most basic of cleaning methods: Cleaning a surface with a dry wipe – this is the “mechanical removal” component of cleaning. It removes roughly 70% of contaminants, which seems like a lot, but is not effective at eliminating microbes – this gets a rating of “Basic”. Best application would be the pre-clean of dirty surfaces before either of the next 2 options is employed. Consider this ineffective against Covid-19.
The next level up is Cleaning with Soap and Water or Alcohol (and others like malt vinegar) – In addition to the mechanical component, we are adding a solution that does two things: 1) the solution loosens contaminants so mechanical removal is more effective, and 2) a layer of solution is left on the surface to deactivate the remaining bugs. – this gets a rating of “Effective”. This is good for day-to-day cleaning of high-touch surfaces.
The top level is Cleaning with a Disinfectant (e.g. Bleach or Hydrogen Peroxide) – when used with a wipe, it marries the mechanical action with a the solution that improves the wiping effectiveness, and leaves a solution layer behind (a registered disinfectant) that kills the concerning virus. This gets a rating of “Best”. Use this protocol in areas of high concern, or compromised surfaces in high touch areas. If AHP is used, disinfection can be accomplished in as little as 1 minute. Other disinfectants can be significantly longer, up to 10 minutes in some cases.
It is important to know that when using disinfectants, it is necessary to clean first and then disinfect, as there may be microbes lying beneath surface contaminants. One step cleaner/disinfectants, such as AHP allow these to be combined, where the addition of surfactants help solubilize the contaminants as the disinfectant kills the viable microbes.
How you wipe a surface clean is also important, so that you do not reapply or simply move around the contaminants. Do not scrunch up the wipe and use a back and forth or circular motion over a surface, then go to another surface and reuse the same wipe again! All this accomplishes is moving the contaminants around, or makings things worse by cross-contaminating other areas. All the work done to clean and disinfect can be undone or left partially complete with improper wiping techniques. So then, what is recommended? In cleanrooms, the most critical of environments, they have been effectively cleaning invisible dirt and microbes for decades. Here are some effective practices:
- Quarterfold the wipe first, providing at minimum four clean sides of the wipe for use when refolded.
- Presaturated wipes are the most efficient. Note: if using a spray bottle, spray the wipe first and then use on the surface. Do not spray the surface to be cleaned and then apply the wipe.
- Wipe unidirectionally with overlapping stokes, fully wetting the surface, with the goal of lifting and removing the contaminants at the end of each stoke. Obviously, this not possible on irregular surfaces, but wiping in one direction (vs rubbing back and forth) is key.
- Refold the wipe and use a new surface. Caution: reusing the same surface promotes redepositing of viable contaminants as well as non-uniform wetting of the surface.
- Allow the surface to remain wet for the full dwell time. Reapply if necessary. The surface can be wiped dry after the dwell time has been reached, if desired.
The most important areas to clean
The final consideration needs to be what areas need to be cleaned. High-touch surfaces should be the first and most frequently cleaned. The CDC recommends they be cleaned daily. They are:
- Doors – push plates, knobs, locks, keys, glass and wood surfaces
- Light switches
- Faucet and flush handles
- Railings and handles
- Tables, chairs
- Supplies brought into the house or facility
- Electronics: Phones, tablets, remotes, keyboards
Electronics are a challenge as they are mostly not compatible with liquids. Follow manufacturers specific recommendations for cleaning and disinfecting if available. If not use a wipe saturated with 70% IPA on it to wipe down the surfaces, making sure not to over saturate the surface.
Other areas that are of significantly lower risk of transmitting infection, such as floors and tables should be addressed periodically as microbes will settle on them, and shoes will track in dirt and other contaminants. Mopping them with a detergent will be sufficient, unless the area is suspect, which then requires a disinfectant to be used. (Please refer to CDC guidance for cleaning suspected or compromised areas.) Carpets, floor rugs and drapes are much more difficult. Remove all visible contamination and clean with appropriate cleaners or consider using a compatible disinfectant for porous surfaces. Using commercial cleaners are also a consideration. Laundering of fabric items that can be easily removed and washed should be considered as well.
Along with everything else mentioned in this article, don’t forget a few common-sense items: Wear gloves when you are cleaning. Clean your hands often. Clean your phone often! Don’t touch your face, nose or eyes! Wear a mask when outside and consider glasses and gloves when shopping.
Pier de Jong Cleanroom Thought Leader
- Covid lifespan on surfaces – Aerosol and surface stability of HCoV19 compared to SARS-CoV-1, Doremalen, Bushmaker, Morris, 3/9/20
- Persistence of coronaviruses on inanimate surfaces and their inactivation with biocidal agents, Kampf, Todt, Pfaender, Steinmann, Elsevier and Healthcare Infection Society, 1/31/20
- What is the best disinfectant for surfaces, Dr. Joseph Mercola 3/25/2020
- Effectiveness of Common Household Cleaning Agents in reducing viability of Human influenza A/H1N1, Plos One, 2010
- List N products with Viral Pathogens and Human Coronavirus claims for use against SARS-CoV-2, EPA.gov, 3/16/20
- Cleaning and Disinfection for Households, CDC 3/26/20
- Novel Coronavirus (Covid-19) fighting products Center for Biocide Chemistries American Chemistry council 3/30/20
- The new corona virus can live on surfaces for 2-3 days – here is how to clean them, Allison Aubrey, 3/14/2020