Traffic Is Way Down Because Of Lockdown, But Air Pollution? Not So Much

With traffic dramatically down in recent months, the United States is in the middle of an accidental experiment showing what happens to air pollution when millions of people stop driving.

The air is clearer. But the pollution declines aren't nearly as large as early indications suggested, according to an NPR analysis of six years of Environmental Protection Agency data.

In some cities, the amount of one pollutant, ozone, has barely decreased compared with levels over the past five years, despite traffic reductions of more than 40%. Ground-level ozone, or smog,...