The novel coronavirus that has caused a global pandemic is also having an enormous impact on the environment, according to new satellite data. As governments around the world have restricted people from moving, industry, air travel and vehicular traffic have grinded to a halt, causing pollution levels to plummet, according to The New York Times.
“This is the first time I have seen such a dramatic drop-off over such a wide area for a specific event,” Fei Liu, an air quality researcher at NASA‘s Goddard Space Flight Center, told CNN. “I am not surprised because many cities nationwide have taken measures to minimize the spread of the virus.”
Areas that have been COVID-19 hotspots, like China and Italy, have already seen huge reductions in air pollution. Now the same trend is happening in major U.S. cities like Los Angeles, Seattle, New York, Chicago and Atlanta where rush hour congestion has vanished as trucks and cars are no longer choking the streets.
“Air pollution levels as observed by satellite are showing drastic improvements in many areas that have been undergoing restrictive quarantines due to COVID-19,” Peter DeCarlo, an associate professor of environmental health engineering at Johns Hopkins University, told Newsweek.
“But it’s [also] very clear that airline passenger numbers are way down, as many countries introduce travel bans and meetings/conferences/work-related travel is canceled. Industrial activity is also reduced, but not necessarily to the extent of traffic. For example, power plants still need to run to produce electricity, water treatment plants still need to continue to treat water, etcetera,” he said.
In Los Angeles, California, as businesses and schools have closed and drivers have stayed off the roads, air pollution has declined drastically and traffic jams have all but vanished.
According to Yifang Zhu, a professor at UCLA’s Fielding School of Public Health, improvements in air quality in recent weeks in the Los Angeles region, long notorious for its traffic and smog, can be partly tied to the coronavirus response.
The region has seen around a 30 percent decrease in PM2.5. This form of pollution, composed of particles smaller than a strand of human hair, are a health hazard because they get into a person’s lungs and bloodstream. Lung disease, difficulty breathing and heart ailments have been linked to this form of pollution.
Zhu says the average levels of PM2.5 for the L.A. area dropped from about 16 micrograms per cubic meter to about 12 micrograms per cubic meter.
“This is significant,” she said. “This is a dramatically changed air-quality level from medium to good.”
For nearly the entire month of March, air quality maps tracking the region’s scores on the Environmental Protection Agency (EPA)’s Air Quality Index were nothing but green—the color that denotes the cleanest air.
Historical data from the EPA suggests that it may have been the longest stretch of clean air since 1980, the earliest year with available data.
March had 24 days—including 20 days in a row—with a daily air quality score below 50, denoting air that’s healthy even for people sensitive to pollution (those with respiratory issues or heart problems, for instance). March 2019 had 14 such days—the highest number for the month since 2006. In March 2008, LA County’s air quality score fell below 50 just once.
“We’re seeing very clean air all around California,” says Bill Magavern, policy director with the Coalition for Clean Air. “This time of year we usually have better air, especially with the rain, but the drop-off in traffic has definitely reduced emissions.”
It’s a small silver lining to a pandemic that’s shut down businesses, closed schools, and put strain on LA’s healthcare system.
Before stay-at-home orders were issued March 16, Zhu said, the EPA’s Air Quality Index, which incorporates multiple air pollutants, including NO2 and PM2.5 (fine particulate matter), was about 60, or in the “moderate” category. Since then, it has improved by about 20 percent and recorded the longest stretch of “good” air quality in March seen since at least 1995.
Zhu noted that emissions and meteorology are playing a role in improving Los Angeles’s air quality, as the weather at this time of year favors less stagnant air conditions, while factories and other emissions sources, such as cars and trucks, have decreased.
She said in an interview that NO2 emissions have been declining in the country overall in recent years because of air pollution regulations and that spring tends to be a period of relatively low concentrations because NO2 breaks down easily in the presence of sunlight.
It will take time for scientists to sort out how much of the variations in NO2 levels in 2020 are from to coronavirus-related changes in human activities, such as reduced driving, compared to changes in weather patterns. However, data NASA released Thursday suggests that the human signal during this pandemic is significant.
Drawing on data from one of its satellites, the agency found that, for the Mid-Atlantic and Northeast, March 2020 had the lowest monthly atmospheric NO2 levels of any March since at least 2005.
Satellite imagery taken over the U.S. in the first three weeks of March shows less nitrogen dioxide over the country than the same period last year, according to data from the European Space Agency.
The satellite emissions data was analyzed for The New York Times by Descartes Labs, a geospatial analysis group. Nitrogen dioxide levels are driven by burning fuels, as well as emissions of cars, trucks, buses, power plants and off-road equipment. Nitrogen dioxide levels can also fluctuate with weather conditions, and experts said quantifying the precise effects of the shutdown on such pollution will take further study.
According to Zhu, the observed air-quality improvement in Los Angeles linked to the coronavirus should not be looked at as only possible during a disaster but rather something that society should strive for during normal times.
“There are technological tools and policy tools to make our society more sustainable,” she said. “We don’t need to have a pandemic just to bring clean air to everybody.”
There’s another factor that has helped to improve Los Angeles’ air quality: weather. With or without people staying home, the weather plays a big role in affecting the daily air quality.
For example, on a typical smoggy day, offshore winds can clear out the smog over downtown Los Angeles. It becomes so clear that people along the coast can see all the way to the mountains. Unsettled or stormy weather can also improve air quality by mixing up the atmosphere and preventing pollutants from building up.
Southern California has experienced a long stretch of rainy days for much of March and the first part of April. The South Coast Air Quality Management District’s “Air Quality Map Index” showed that many cities were in the green or good quality range since about March 7 – one week before the Stay at Home order went into effect.
The AQMD analyzed CalTrans traffic sensors on freeways throughout the basin and found notable traffic reductions in March: 33% in light-duty vehicles and 20% in heavy-duty vehicles.
The AQMD believes that the weather is the most significant factor driving day-to-day changes in air quality. Meteorological factors must be removed or one must look at a long timeframe before quantifying effects of reduced emissions.
Preliminary data from the European Space Agency’s Sentinel-5P satellite show that atmospheric levels of nitrogen dioxide, which are influenced in large part by car and truck emissions, were considerably lower over the usually smog-ridden metropolis in the first two weeks of March compared to the same period last year. The car-dependent city normally features some of the highest smog levels in the country.
In 19 of the last 20 years, the American Lung Association named Los Angeles the smoggiest metropolitan area in the United States. INRIX, a company that analyzes traffic data from vehicle and phone navigation systems, recently found the city’s traffic congestion to be the sixth-worst in the nation.
Los Angeles’s famous rush-hour congestion has virtually disappeared. On Wednesday at 8 a.m., traffic in the city was moving 53 percent faster than it usually does on a Wednesday morning, according to data from INRIX. At 5 p.m., when the freeways are typically congested, traffic was moving 71 percent faster than usual.
As a measure of how much that traffic congestion has dissipated, Inrix found that cars were moving 63 percent faster than average at 5:30 p.m. last Tuesday.
“There’s basically no rush hour anymore, or at least not what we would recognize as a rush hour,” said Trevor Reed, a transportation analyst at INRIX. He said that traffic has decreased even more sharply in the evening because that’s when people are normally running errands in addition to commuting home, but many of those activities have now been put on hold.
The New York Times noted that freeway traffic in Los Angeles, which is usually at a standstill during rush hour, was moving at a brisk 71 miles per hour.
Similar changes can be seen in the Bay Area, where local officials on Monday ordered the region’s 6.7 million residents to shelter in place. Since then, the number of cars and trucks crossing eastbound on the Bay Bridge each day between San Francisco and Oakland has fallen roughly 40 percent compared with two weeks ago, according to data from monitoring stations operated by the California Department of Transportation.
While that’s a sign that people are heeding the advice of public health experts, it’s yet another warning that the nation’s economy is facing serious peril. Traffic and congestion, while often a source of annoyance, are also a telltale sign of bustling economic activity. On Thursday, March 19, California Gov. Gavin Newsom extended the shelter in place order to cover the entire state.
Magavern points out that this could even aid those afflicted with COVID-19, the disease caused by the novel coronavirus. The European Public Health Alliance warned last week that residents of cities with poor air quality are “more at risk” from the disease, which can cause severe respiratory issues.
According to the California Air Resources Board, the last time ozone (a major contributor to smog) in the Los Angeles area reached unhealthy levels was in February. Over the summer, the region saw unhealthy ozone levels every day for more than two straight months.
Still, Magavern says, a global pandemic is not a worthy trade for cleaner air.
“This is not the way we want to reduce emissions,” he says.
The coalition has long advocated for policies aimed at reducing greenhouse gases caused by transportation—the largest source of emissions in California. Those include incentives to get more drivers to switch to electric vehicles, or simply stop driving so often.
“This is a reminder that the vast majority of our air pollution comes from the transportation of people and goods,” Magavern says.
Romel Pascual, director of open streets festival organizer CicLAvia, says he’s hoping that Angelenos use this time stuck at home to rediscover their own neighborhoods. Though local officials have ordered residents not to leave the house except for essential needs, walking and outdoor exercise has been encouraged—so long as people aren’t doing it in groups.
“I’m walking in my neighborhood more than ever before,” he says. “I’m noticing a lot more folks walking. You don’t have to go some [other] place to experience the environment; you can listen to the birds flying by and look at the trees almost anywhere.”
Bryn Lindblad, deputy director of Climate Resolve, says she’s hopeful people will be able to retain some of the habits they develop during this time.
“It’s ironic to me that it’s a quarantine order that’s getting people to do what public health experts have been advising for years—walking around the neighborhood,” she says. “I’m hoping people hold on to that a little bit. After this whole rigmarole is over, we can still keep our streets nice and inviting to people.”
There’s a growing recognition that the coronavirus can be more harmful to those with greater exposure to air pollution, making it a potential risk factor along with such underlying health conditions as diabetes, asthma and high blood pressure.
A study published this week from researchers at Harvard’s T.H. Chan School of Public Health concludes a small increase in long-term exposure to fine particulate air pollution causes a large increase in the risk of dying of covid-19, the disease caused by the coronavirus.
“The study results underscore the importance of continuing to enforce existing air pollution regulations to protect human health both during and after the COVID-19 crisis,” the study states.
For example, the study, which examined more than 3,000 U.S. counties, found that each increase in long-term exposure to fine particulate pollution of one microgram per cubic meter is associated with a 15 percent greater likelihood of dying of covid-19. This stark difference may be explained by the lung damage such pollution causes over time. Covid-19 targets the lungs and can cause patients to develop pneumonia.
In addition to cuts in NO2 emissions, the coronavirus lockdowns have caused the relentless climb in carbon dioxide emissions to have a temporary hiccup, and the cancellations of tens of thousands of flights also could have consequences for our planet by reducing planet-warming emissions and high-altitude cirrus cloud formations.
Ryan Stauffer, a specialist in air pollution at NASA, said additional studies are needed to determine how the coronavirus-related mitigation measures have affected air pollution. “We all have this hunch” about how air pollution has changed, Stauffer said, adding, “The longer this goes on, the more we will see.”