Oregon DEQ measurements illustrate remarkable decline in airborne pollutants

Chuck Thompson, April 28, 2020. If you think you’ve been able to see those mountains on the horizon a little more clearly in recent weeks, you’re not imagining things. Partly a result of stay-at-home orders related to the COVID-19 pandemic, air quality across the Columbia River Basin has dramatically improved.

“Over the past few weeks, we’ve seen about a 40 percent reduction in several pollutants related to vehicle emissions, specifically nitrogen oxides and black carbon, which is also known as soot,” said Laura Gleim, spokesperson for the Oregon Department of Environmental Quality (DEQ).

DEQ’s numbers track neatly with traffic figures from the Oregon Department of Transportation (ODOT).

“In general traffic has declined about 40 percent pretty consistently around the state since Governor (Kate) Brown’s ‘stay home’ order,” according to ODOT spokesperson Don Hamilton. Governor Brown’s COVID-19-related order came on March 23.

On a typical Monday afternoon, drivers might despair at joining traffic on Portland’s Banfield Expressway (I-84). These days it’s mostly smooth sailing.

Though fewer vehicles on the road helps, the similar numbers gathered by each agency don’t necessarily indicate a direct alignment between percentage decrease in traffic and percentage improvement in air quality. In other words, it’s not all about COVID-19.

“It’s important to note that some of the fluctuation we’re seeing is because of changes in weather—wind speed, direction, temperature,” said Gleim. “Pollutants rise and fall based on weather.

“There’s also less smoke in the air from fires right now. There are fewer controlled burns going on, it’s warming up so people are using their woodstoves less, and we thankfully haven’t seen any major wildfires yet. This has all led to cleaner and clearer air quality in the state. We’re able to see faraway mountains, for instance.”

DEQ figures for late March show average concentrations of nitrogen oxides and black carbon down between about 27 to 32 percent from the same period in 2019.

Trending: cleaner air

Oregon DEQ tracks several air pollutants in vehicle emissions at an air-monitoring site near I-5 in Tualatin, just south of Portland. It analyzes data for nitrogen oxides (presented in parts per billion) and black carbon (presented in micrograms per cubic meter).

Two DEQ charts illustrate the dramatic improvements in air quality since the COVID-19 crisis began.

[/media-credit] Black carbon emissions DEQ April 2020.

[/media-credit] Nitrogen Oxides emissions, DEQ April 2020.

 DEQ’s Tualatin monitoring site can serve as an indicator of statewide trends. DEQ doesn’t monitor for specific pollutants in other areas of the state because total traffic volume is much lower outside the Portland-metro area. Lower traffic volume results in lower ambient concentrations of vehicle emission pollutants.

 “We’re tracking nitrogen oxides and black carbon specifically during this period because they’re good indicators of vehicle emissions more broadly,” said Gleim.

 Not clear everywhere

In other parts of the Columbia River Basin, it’s still too early to definitively say what effect, if any, COVID-19 shelter-in-place restrictions are having on air quality.

“There’s some significant air quality differences in some cities and areas. In Idaho, we just aren’t seeing that quite yet,” said Steve Miller, air quality data bureau chief for the Idaho Department of Environmental Quality. “It is still too early to definitively quantify any differences in air quality that may be occurring due to COVID-19 and its effects on commuting and other things.

“Additionally, we have been having primarily good air quality in Idaho prior to and during the COVID-19 event, so it is more difficult to decipher such information.”

While vehicle traffic has been reduced across the Pacific Northwest (and world) as a result of COVID-19 regulations, pollutant particle levels in the air aren’t consistent across the region. In fact, in some densely populated residential areas, air quality has gotten worse.

On April 20, Tacoma’s News Tribune reported air quality in Puget Sound has actually declined this spring.

 “With many Puget Sound-area residents staying home, people have been using wood-burning stoves for home heating. Others have been making outdoor fires,” according to the News Tribune.

The Seattle Times cautioned those pinning improvements in air quality on broader issues related to global climate change shouldn’t get their hopes up just yet. In the short term, reduced car emissions won’t make a difference in global warming, according to the Times.

“A lot of people are saying this is good for the climate problem. No, not really,” the Times quoted Pieter Tans, a senior scientist with the National Oceanic and Atmospheric Administration’s Global Monitoring Division.

View from space

In general, however, air quality has improved as COVID-19 shelter-in-place orders have led to decreases in travel and traffic around the world.

NASA’s Aura satellite data—which orbits 438 miles above the Earth—has returned images that show remarkable decreases in pollution over China, India and other countries.

This fascinating NASA slide graphic shows the incredible impact of stay-home orders on pollution in the Northeast United States.

“March 2020 shows the lowest monthly atmospheric nitrogen dioxide levels of any March during the Ozone Monitoring Instrument data record, which spans 2005 to the present,” according to NASA. “In fact, the data indicate that the nitrogen dioxide levels in March 2020 are about 30 percent lower on average across the region of the I-95 corridor from Washington, D.C. to Boston than when compared to the March mean of 2015-19.”

The East Coast is far beyond views from the Columbia River Basin. But the NASA pictures show an undeniable if unintended impact of stay-home orders. At least in the short-term, distant views are improving.