It may have been tough to enjoy it, gulping air through a mask while avoiding other humans, but D.C. had the lowest smog levels in many decades this summer.

There were only two code-orange days, when the air is considered unhealthy for sensitive groups. Last year, by comparison, there were 10 code orange days.

Three factors were at play, according to a new report by the Metropolitan Washington Council of Governments. Pandemic shutdown restrictions meant less pollution from cars, the weather was cooler and wetter than average, and decades of efforts to curb pollution are continuing a downward trend in smog in the region.

In the ’90s, it wasn’t unusual to see a summer with more than 80 days of unhealthy air — including some code purple, or “very unhealthy” days.

Jen Desimone, air program chief at MWCOG, credits a combination of federal, state, and local policies for driving down smog levels over the past 20 years. These include stricter vehicle efficiency standards, limits on pollution from power plants, and renewable energy and energy efficiency programs.

“We have seen over the long term that has made a significant improvement in regional air quality,” said Desimone.

In terms of weather, May was unseasonably cool, and August was unusually wet. Those factors inhibit the formation of smog, which is created by a chemical reaction between oxides of nitrogen (NOx), volatile organic compounds (VOC), and sunlight/heat. NOx pollution comes mostly from vehicle emissions, while VOC pollution comes from vehicle exhaust as well as industry and household chemicals.

Stay-at-home orders dramatically reduced traffic in the region, meaning less NOx and VOC pollution in the air. NASA satellite data from March, at the beginning of the shutdown, showed 30% less nitrogen dioxide in the air, compared to the 2015-2019 average.

Still, even with dramatic air quality improvements in recent years, and the unusually clean pandemic air, the region is not meeting standards set by the Environmental Protection Agency.

“We’re very, very close to meeting the standard,” said Desimone. “In fact, we’re just slightly above it.”