Since the coronavirus has become a threat, many of us have been doing a lot more cleaning at home, spraying and wiping just about everything in sight, especially high-contact surfaces like door knobs and faucet handles.
But many of us are used to giving a surface a quick spray, followed by one or two wipes, which may not leave enough time for the product to work. And once you start reading the labels of cleaning products carefully, it gets really confusing. Several readers have pointed out that disinfectant wipes and spray cleaners have different instructions on their labels for how long a cleaner should stay on a surface to effectively kill germs, ranging from 30 seconds to four minutes or even up to 10 minutes. In addition, some labels recommend cleaning before using a disinfectant.
So what is the right way to clean? We have spoken with infectious disease scientists and microbiologists who study and test cleaning products to answer your questions about cleaning up during the coronavirus era. The bottom line: Whether you’re worried about the coronavirus or other germs hiding in our homes, many of us clean up too quickly for the disinfectant to do its job.
Here’s what the experts said.
How long should a disinfectant stay on a surface to kill germs?
You probably need to leave your disinfectant on the surface you are cleaning for much longer than you think.
“The longer you can keep him in touch, the better,” said Dr. Andrew Janowski, a pediatric infectious disease instructor at Washington University School of Medicine St. Louis Children’s Hospital. “What I do at home: I wait about a minute if I apply a spray and then wipe. “
To find out how long is recommended for a specific product, check the label. Guidance can range from 30 seconds to several minutes of contact before wiping. Note that some products may claim to disinfect, which means that they reduce the level of certain bacteria, but not viruses. A claim regarding a disinfectant means that the product destroys or inactivates both the bacteria and the viruses indicated on the label.
Even cleaners from the same brand have different contact times. My Clorox bleach bottle indicates five minutes of contact time, while Clorox Clean-Up Cleaner + Bleach advises 30 seconds. Clorox Anywhere Hard Surface reports two minutes (but promises to kill only bacteria, not viruses), while Clorox Disinfecting Wipes reports four minutes. Even among similar Lysol brand wipes, the recommended contact time varies – the The lavender scented wipe recommends 10 minutes of contact time, while the lemon-lime scented wipe indicates four minutes.
Why are the recommended contact times so different? It depends on the bacteria and viruses that the product claims to kill. To make a disinfection claim, a product must go through a strict testing process defined by a country’s regulatory agencies. In the United States, it’s the Environmental Protection Agency. To test a disinfectant, scientists cover a surface with a large dose of the organism studied. They then spray the surface with a disinfectant and let it sit for a while before testing to determine if any of the organisms remain viable.
These tests are essentially worst-case scenarios using excessively high concentrations of germs – about 100,000 organisms per centimeter – which is much more than would typically be found in a domestic setting. “Most common surfaces in homes and hospitals contain less than 100 organisms per square centimeter,” said Dr. David Weber, professor of medicine and epidemiology at the University of North Carolina at Chapel Hill.
But even if the advice on contact time is probably exaggerated, to be sure that a surface has been completely disinfected, you should pay attention to the disinfection time recommendations on the label, especially when someone in the house is sick. In some cases, contamination by organisms can reach very high levels in a home – such as when working with raw chicken in a kitchen or when someone in the house is sick and an area has been contaminated with stool or vomiting. And certain organisms, such as norovirus, which causes severe gastrointestinal symptoms, are particularly difficult to eliminate and can cause illness in infinitesimal doses.
Why does the label say that a surface needs to be cleaned before use a disinfectant? Do I really need to clean twice?
If your surface is covered with crumbs, grime or spilled food, then yes, you need to clean up debris and dirt before using any disinfectant.
“For a germicide to work, it must touch the germs,” said Dr. Weber, who consulted for PDI, a company that manufactures disinfectants. “If you have a layer of dirt, the dirt can protect the bacteria. Cleaning must precede disinfection. “
Some cleaners promise to both clean and disinfect, but even these labels advise to pre-clean a very dirty surface.
The label on my disinfectant wipes says that I have to use them for four minutes. Do I really have to wipe that long?
When the wipes are tested in the laboratory, the clock starts with the first wipe and continues until the surface dries. So you don’t need to wipe for four full minutes (or at the time indicated on the label). The goal is for the wiping time and drying time to last four minutes, says Haley Oliver, microbiologist and associate professor of food science at Purdue University.
In a recent study on disinfectant wipes, Dr. Oliver and his colleagues tested a six-inch square formica covered with Staphylococcus aureus bacteria. The surface was wiped four times with a disinfectant wipe and left to dry. Five of the six products tested remained wet on the surface until the contact time with the label was reached. A product dried 15 seconds too early, but it still worked well against germs.
“I think it’s important to be aware of the contact time,” says Dr. Oliver, whose research includes working with Diversy, a leading producer of cleaning and disinfection products. “If this is my house and I am wiping, I want to see that the wipe has deposited liquid on this surface. “
I often use a single wipe to clean multiple surfaces. Do I have to use a new wipe every time to avoid spreading germs?
You can use a wipe to clean multiple surfaces. As long as the wipe stays wet, which indicates that it still contains a lot of cleaner, you don’t have to worry about the spread of organisms. That said, most of the experts I’ve spoken to prefer not to mix the pieces. So they would use a wipe on multiple surfaces in a bathroom, for example, but they would not use the same wipe in the kitchen.
Dr. Oliver notes that there are no official guidelines on the area that a cloth can cover. The key to disinfecting with wipes is to know when your wipe lacks disinfectant. “If it is not wet, then you do not come into contact with microbes with the chemistry that was expected,” says Dr. Oliver. “If you run out of ingredient and your towel is dry, you could pass these organisms on. “
What is the best cleaner to get rid of coronaviruses?
Product labels will specifically indicate what types of bacteria and viruses have been tested. But because SARS-CoV-2, the virus that causes Covid-19, is so new, most cleaning products have not been tested against it. The E.P.A. however published a list of products that can kill the virus because they are proven to work against harder-to-kill viruses or other types of coronavirus.
The good news is that the new coronavirus is actually much easier to kill than many of the organisms previously studied. So it’s likely that even if you didn’t follow the contact time recommendations for disinfectants, you probably killed the virus. But you must follow the meaning of the label to fight more difficult to kill germs such as e-coli, salmonella or staphylococci.
“It is important to note that these recommendations are generic and generally based on the time it takes to kill bacteria – for example, Staph and Strep, which are much more difficult to kill than a virus like SARS-CoV- 2, “said Dr. Daniel R. Kuritzkes, chief of the infectious disease division at Brigham and Women’s Hospital and professor at Harvard Medical School. “Shorter exposure times are most likely still effective enough to prevent Covid-19. “