Midday sunlight can kill coronavirus in 34 minutes in most US, world cities: Study

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Exposure to midday sunlight can inactivate the coronavirus within 11 to 34 minutes during summer in most US cities and other cities around the world, a study suggested.

“Ninety percent or more of SARS-CoV-2 virus will be inactivated after being exposed for 11-34 minutes of midday sunlight in most US and world cities during summer,” the study published early June in the Photochemistry and Photobiology journal.

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The World Health Organization (WHO) defines “viral inactivation” as “a process of enhancing virus safety in which the virus is intentionally ‘killed’.”

The study explains that “Ultraviolet radiation in sunlight is the primary virucidal agent in the environment.” Virucides are substances that destroy viruses.

The researchers question whether the stay-at-home orders, curfews and lockdowns effective in containing the spread of the coronavirus and suggest that there is an environmental element to the spread of COVID-19 aside from direct interaction between people.

“If we accept a possible virucidal role of sunlight during coronavirus pandemics, then forcing people to remain indoors may have increased (or assured) contagion of COVID-19 among same house-hold dwellers and among patients and personnel inside the same hospital or geriatric facilities,” the researchers said.

“In contrast, healthy people outdoors receiving sunlight could have been exposed to lower viral dose with more chances for mounting an efficient immune response,” they added.

The study estimated how long it would take to inactivate the coronavirus in some cities around the world at noon in summer, during maximum solar exposure:


Miami, Florida: 14+ minutes

Houston, Texas: 16+ minutes

Phoenix, Arizona: 18+ minutes

Atlanta, Georgia: 18+ minutes

Los Angeles, California: 18+ minutes

Washington, D.C.: 21+ minutes

Philadelphia, Pennsylvania: 22+ minutes

New York City, New York: 22+ minutes

Chicago, Illinois: 22+ minutes

Boston, Massachusetts: 23+ minutes

Central and South America:

Bogota, Colombia: 11+ minutes

Mexico City, Mexico: 11+ minutes

Sao Paulo, Brazil: 13+ minutes

Buenos Aires, Argentina: 19+ minutes


Barcelona, Spain: 22+ minutes

Paris, France: 28+ minutes

London, UK: 30+ minutes

Moscow, Russia: 34+ minutes

Middle East:

Baghdad, Iraq: 18+ minutes

Tehran, Iran: 19+ minutes

Istanbul, Turkey: 22+ minutes


Kinshasa, Congo: 11+ minutes

Lagos, Nigeria: 11+ minutes

Khartum, Sudan: 11+ minutes

Cairo, Egypt: 16+ minutes


Mumbai, India: 11+ minutes

Shanghai, China: 16+ minutes

Seoul, South Korea: 18+ minutes

Tokyo, Japan: 20+ minutes

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