White House official says sunlight, humidity help kill coronavirus

WASHINGTON — Direct sunlight and high humidity can kill the coronavirus in minutes, according to new research announced on April 24 by a senior U.S. official in a press conference with President Donald Trump.

A summary of research from the Department of Homeland Security found that when the temperature was 70 to 75 degrees Fahrenheit (21 to 24 degrees Celsius) with 20 percent humidity, the coronavirus' half-life, or rate of decay, was 18 hours on a nonporous surface.

When humidity was raised to 80 percent, the halflife fell to six hours.

When sunlight was added, the half-life dropped to just two minutes.

When the virus was aerosolized in droplets that hang in the air, its half-life was one hour when the temperature was 70 to 75 degrees Fahrenheit (21 to 24 degrees Celsius) with 20 percent humidity.

When sunlight was added to the equation, its half-life was only one-and-a-half minutes.

The new research was announced to reporters at the White House by William Bryan, science and technology advisor to the Department of Homeland Security secretary, who displayed the information on slides.

The study, which was carried out by the National Biodefense Analysis and Countermeasures Center in Maryland, has not yet been released for review and is still awaiting external evaluation.

Bryan's summary of the research leaves many questions unanswered, such as the intensity and wavelength of the ultraviolet light used in the experiment.

In a statement sent to CNN, the Illuminating Engineering Society, a non-profit industry group, said, "Ultraviolet disinfecting 'wands' or other ultraviolet products for residential use — as they are inadequately proven and unregulated — may pose a safety hazard and are unlikely to provide the protection expected."