Hazards Human Health

Sunrise, sterilize, sunset, repeat: Heat and sunshine work together to kill COVID-19

Efstratiou, M.A. & Tzoraki, O. (2021) Coronavirus survival on beach sand: Sun vs COVID-19. Marine Pollution Bulletin 167: 112270. DOI: 10.1016/j.marpolbul.2021.112270

 

Sandy beaches are a popular outdoor activity. By Tom Lanik – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=5569411

COVID-19, the disease caused by the coronavirus SARS-COV-2, is spread mainly person to person transfer of the virus through respiratory droplets. Outdoor activities therefore pose a much safer way to gather than indoors, because fresh air dilutes and dissipates viral particles. Beaches have become a popular outdoor gathering space over the past year, as people look for ways to socialize while socially distanced. Summer vacation is coming up, but as people make plans to head to the beach, should we be worried about COVID-19?

 

It is possible to be infected by being exposed to viral particles on contaminated surfaces. Some regulators are concerned that if people are frequenting beaches there could be transmission of COVID-19 though contaminated beach sand. Viral particles could be transferred to sand by respiratory droplets from someone infected with COVID-19. However, when these pieces of virus land on the sand they are also exposed to heat and UV radiation from the sun, which could kill the virus.

In this discussion paper, scientists from Greece pull together information from different studies and talk about what we know about heat, UV radiation, and SARS-COV-2 to lay out a convincing case as to why there is little risk of catching COVID-19 from sand at the beach, and to why local authorities shouldn’t try and disinfect beaches to kill the SARS-COV-2 virus.

SARS-COV-2 Biology

Coronaviruses, like the SARS-COV-2 virus that causes COVID-19, are RNA enveloped viruses, meaning they are covered by a membrane or “envelope”. This membrane also has four different types of proteins that are involved in how the virus reproduces and infects people. Currently, researchers think that SARS-COV-2 can survive for a few days outside of living cells, which is why disinfecting surfaces and washing hands are so important.

SARS-COV-2, the coronavirus that causes COVID-19, is covered by a viral "envelope" with different types of proteins.
SARS-COV-2, the coronavirus that causes COVID-19, is covered by a viral “envelope” with different types of proteins. By Felipe Esquivel Reed – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=87846813

How does the environment kill COVID-19?

Heat is a common, natural way of destroying bacteria and viral particles. High temperatures affect how these cells and particles function, because most cells are designed to work best within a certain range of temperatures. Viral envelopes, like the membrane that surrounds SARS-COV-2, are particularly fragile and can be destroyed at high temperatures over 100°F. In addition, ultraviolet (UV) radiation, the type of radiation that comes from the sun, can also damage viral particles. SARS-COV-2 is particularly susceptible to UV radiation.

The temperature of sand on beaches can be over 100°F when the air temperature is only 75°F. At an air temperature of 90°F, beach sand can be up to 120°F. Heat, therefore, can play a role in killing the COVID-19 virus on beaches. Since the virus is also killed by UV radiation, both the heat and sun’s rays can kill SARS-COV-2 and dramatically reduce the chance that anyone will be infected from viral particles on beach sand.

What do scientists recommend?

Because COVID-19 likely doesn’t survive on beach sand in warm weather, the scientists in this paper recommend letting nature do the work for us, rather than trying to disinfect beaches. The most common methods used to kill COVID-19 all use chlorine disinfectants, but these disinfectants can kill not only COVID-19 but also the animals and microorganisms that live on the beaches and are important for the local ecosystem. Spreading chlorine disinfectants can also cause runoff that will contaminate the water nearby. Chlorine is especially harmful to animals living in water and soil, and can affect the immune system, the blood, heart, and even respiratory system. Therefore, the less we need to use chlorine-based disinfecting methods, the better.

Overall, as long as social distancing is maintained, taking a trip to the beach is a relatively safe, low risk activity. As the weather gets warmer, beach trips and other outdoor activities like a picnic in the park, hiking, or kayaking are great ways to maintain social distancing while seeing friends and family.

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