So let's take a look by the numbers.

Los Angeles is usually one of the smoggiest cities in the U.

S.

But this guy's there have been transformed in recent weeks.

According to the E.

P.

A s Air Quality Index, E L A area had 24 days in March with a daily air quality score deemed good.

That includes 20 days in a row, the longest stretch of clean air in 40 years, when such data was first tract.

Combined with a rainy march, reduced traffic has played a huge part in reducing pollution in L.

A and other cities.

In San Francisco, traffic was down 40% on the Bay Bridge in the week after California's stay at home order went into effect, according to the state's Department of Transportation.

Data from Las Vegas also shows about a 33% decline in air pollutants caused by vehicle emissions in late March, and the pollution reduction has been global.

India's capital of New Delhi saw 71% drop in air pollutants in one week, according to government data, after that nations 1.3 billion citizens began a 21 day locked down last month.

NASA satellites detected similar massive drops and pollutants over China in February, although pollution is now returning as the nation reopened, showing much of this reduction will only be temporary.

Hi, everyone, George Stephanopoulos here.

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