Millions of people who are staying home from work and school are creating an unintended consequence for the environment: cleaner air.
Shelter-in-place orders are only about a week old, but air pollution experts say they are seeing drops in smog across the Bay Area — a pattern that already has played out in China, Italy and other parts of the world where efforts to slow the spread of coronavirus have significantly reduced motor-vehicle traffic and industrial activity.
“We are seeing clean air quality right now. When we look at our measurements, it is below what we were seeing a few weeks ago, for sure,” said Phil Martien, director of assessment, inventory and modeling at the Bay Area Air Quality Management District in San Francisco.
Martien and other air scientists say it’s still too early to calculate exactly how much less soot and smog is in the air across Northern California due to the coronavirus pandemic. That’s because shelter-in-place rules only took effect a few days ago. Weather changes also can have a big impact on day-to-day air pollution levels. Wet weather washes particles out of the air, hot weather exacerbates smog, and breezy weather can blow pollution to other parts of the state.
Nevertheless, anyone walking, biking or driving outdoors can see the blue skies. And other clues are beginning to surface.
Traffic counts at Bay Area bridges have been roughly 70% lower in recent days than normal, Martien said. Because motor vehicles are responsible for about 30% of the fine particulate matter, or soot, in Bay Area air, that means those tiny particles, which lodge deep in the lungs and can cause heart and lung problems, have probably declined by at least 20%, he said.
Similarly, nitrogen oxides, chemicals that are emitted from burning fuels and contribute to smog, are down roughly 40% using similar estimates, he said. And carbon dioxide, a leading greenhouse gas, is off roughly 20% due to the decline in Bay Area driving, Martien said.
Other factors, such as whether people are burning more wood at home in their fireplaces or how much pollution from large factories is being reduced, are still not yet known. It will take months to investigate. But health benefits are likely.
“This is not how we want to see air quality go down,” Martien said. “I suspect this is just a temporary reduction. But definitely, for the elderly and people who have health issues like heart issues or breathing difficulties, clean air is especially beneficial.”
Every day since March 14, the EPA Air Quality Index has reported all nine Bay Area counties bathed in green on its color scale, for good quality air. It’s rare to have so many consecutive clean-air days.
And last week, air-quality sensors that measure particulate matter showed the lowest average readings of any week so far in 2020 — down 21% in Oakland, 36% in San Jose and 41% in San Francisco from the week before.
Blue skies this month show what the future might look like when more of California’s vehicles are electric, said Ronald Cohen, a chemistry professor at UC Berkeley who studies Bay Area air trends. But for now, they symbolize lost jobs and lost economic activity.
“As wonderful as it is to breathe clean air, in the short term we want all that pollution to come back because we want the economic activity to come back,” Cohen said.
Most months, Bay Area air quality is generally cleaner than in many parts of the world, including in Los Angeles and the Central Valley.
That’s because 50 years of air pollution laws have required everything from unleaded gasoline to vehicle smog checks to scrubbers on factory smokestacks. The region’s high-income population also tends to drive more electric vehicles and newer vehicles than people in other areas, and there is only a modest amount of heavy industry like oil refineries, and a mostly mild climate.
However, in high-pollution places such as China — where coal-fired power plants, steel mills and 340 million vehicles belch out dangerous levels of smog daily — the coronavirus has sparked far more dramatic changes.
NASA scientists have reported drops of up to 30% in smog-forming pollutants over central and eastern China in January and February, compared to the same months in recent years, based on satellite measurements. They attribute some of that drop to strict limits on driving and other activity during the outbreak.
The big improvement in air quality, which already has started to wane as China’s economy begins to slowly ramp back up, saved thousands of lives, scientists estimate.
Through Sunday, a total of 81,093 cases of COVID-19 have been documented in China, with 3,270 deaths, according to the World Health Organization.
Marshall Burke, an assistant professor of earth system science at Stanford University, downloaded air pollution data from particulate sensors at U.S. consulates in four Chinese cities — Beijing, Shanghai, Chengdu, and Guangzhou. He compared the levels in January and February with prior years and calculated in a recent article that the cleaner air saved the lives of at least 1,400 children under age 5 and 51,700 residents over age 70 who otherwise would have died from heart attacks, emphysema, extreme asthma and other health problems triggered by bad air pollution.
In an interview, Burke noted that it’s likely that many more lives will be saved from the temporary clean air in China than will be lost to COVID-19. That doesn’t mean coronavirus is beneficial, he stressed. Although some lives will be saved with far fewer traffic fatalities during the emergency than normal, the economic downtown, additional poverty and medical chaos from the economic impacts likely will result in many deaths that cannot yet be measured.
“This is not a silver lining. The pandemic is incredibly destructive,” Burke said. “But it shows that when we really disrupt the economy and shut things down, we emit a lot less pollution, and that affects our health.”
Similar health improvements occurred during the 2008 Beijing Olympics, when the Chinese government idled factories and reduced driving, resulting in about a 20% reduction in air pollution for two months.
Because the Bay Area’s air is dramatically cleaner than China’s — it actually reached the level of some Chinese cities when smoke from the Camp Fire drifted south in November, 2018, blanketing the region — the number of Bay Area deaths reduced from air pollution during the coronavirus shutdown is probably about 10 a week, Burke calculated.
His take-away? The crisis may be showing society new ways to function that could improve health. Do so many people need to fly to business meetings when they could hold web conferences, for example?
“The calculation is perhaps a useful reminder,” Burke wrote in his post, “of the often-hidden health consequences of the status quo, i.e. the substantial costs that our current way of doing things exacts on our health and livelihoods. Might COVID-19 help us see this more clearly?”
