Is liquid chalk an effective disinfectant of SARS-CoV-2 and influenza viruses?

Many hand sanitizers contain around 60-80% alcohol, which is why they are useful in preventing the spread of infectious diseases. Hand sanitizer use has been a key control measure in limiting the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission during the ongoing coronavirus disease (COVID-19) pandemic.

Study: Liquid Chalk Is an Antiseptic against SARS-CoV-2 and Influenza A Respiratory Viruses. Image Credit: Carlos Gutierrez Photo / Shutterstock

Liquid chalk as a hand sanitizer against SARS-CoV-2

Liquid chalk, a sanitizer commonly used in gyms, is said to act as an effective disinfectant for SARS-CoV-2. However, this has yet to been proven experimentally. Liquid chalk comprises magnesium carbonate (chalk), 40 to 80% alcohol (ethanol, methanol or isopropanol), water, and other additives such as resins or proprietary materials. When liquid chalk is applied to the hands, it distributes across the surface of the hand and dries into a thin layer of chalk as the alcohol evaporates.

A recent study, published in the American Society for Microbiology’s journal, mSphere, evaluated the use of many liquid chalk products as antiseptics against the transmission of highly pathogenic human viruses such as influenza A virus (H1N1), SARS-CoV-2, (IAV), and norovirus in a mouse norovirus (MNV) model. The researchers applied chalk before or after virus inoculum and determined the recovery of infectious virus to mimic its use in the gym setting.

The researchers observed that the application of chalk before or after contact with the virus led to a significant reduction in recovery of infectious influenza and SARS-CoV-2 viruses but had a negligible impact on norovirus. These observations show that liquid chalk is an effective antiseptic that can be used in social gym settings and during major sporting events such as the Olympics to curb the spread of COVID-19 in the community.

First report to directly compare sensitivity or resistance of highly infectious respiratory viruses to liquid chalk

According to the authors, previous studies on liquid chalk did not investigate its efficacy against highly infectious viral pathogens, and this is the first report that directly compares two highly infectious respiratory viruses (SARS-CoV-2 and influenza virus) as well as fomite-transmitted norovirus for their sensitivity or resistance to liquid chalk. The findings show that highly pathogenic respiratory viruses,
such as the influenza A virus, are also sensitive to liquid chalk compared with SARS-CoV-2. One additional finding observed by the authors is that when the alcohol evaporates from the liquid chalk, and it dries up, it is still effective against both SARS-CoV-2 and the influenza A virus.

Interestingly, not all chalks were equally effective against the viruses, although all of them had various proportions of alcohol. Also, noroviruses were found sensitive to alcohols, but to liquid chalk. These findings show that resistance or viral sensitivity cannot be attributed to just the alcohol under the conditions tested.

Pandemic-related restrictions have led to the closure of recreation centers and gyms to prevent contact transmission from potentially contaminated gym equipment. Observing the antiviral activity of liquid chalks against SARS-CoV-2 may help in decision-making about the reopening of gyms in the near future. This is important because gym closures due to COVID-19 can have a negative impact on personal fitness, mental health, and well-being.

Our study has shown that the implementation and application of liquid chalk in communal social gym settings is effective in reducing the infectivity of respiratory viruses, and this supports the use of liquid chalk in major sporting events to restrict the impact of COVID-19 on our communities,” conclude the researchers.

Written by

Susha Cheriyedath

Susha has a Bachelor of Science (B.Sc.) degree in Chemistry and Master of Science (M.Sc) degree in Biochemistry from the University of Calicut, India. She always had a keen interest in medical and health science. As part of her masters degree, she specialized in Biochemistry, with an emphasis on Microbiology, Physiology, Biotechnology, and Nutrition. In her spare time, she loves to cook up a storm in the kitchen with her super-messy baking experiments.