This year was supposed to be a milestone for environmentalists worldwide: the 50th anniversary of Earth Day.
"It’s a shame," Ned Mulcahy, the staff attorney for the nonprofit Group Against Smog & Pollution (GASP), told ABC News. "Part of celebrating the environment is being out in the environment."
Mulcahy and other environmentalists, however, have said the pandemic has given them a glimmer of hope. Researchers around the world have seen a drop in air pollutants as a result of fewer cars on the road and exhaust from factories due to the shelter-in-place orders issued by world governments.
"We’re seeing in some places the best air quality in decades," Bill Magavern, the policy director for the Coalition for Clean Air, told ABC News. "It is very good for our lung health that air pollution is down during this time of crisis."
While scientists warn that air quality will likely take a hit once shelter-in-place orders are lifted, the temporary change in the environment could spur environmental regulations and policies that could lead to better air in the long term.
Two weeks ago, satellite data from NASA showed a 30% drop in air pollutants in the northeastern section of the U.S. during March. The air had particularly low quantities of nitrogen dioxide, or NO2, according to Barry Lefer, a NASA air quality scientist.
"Power plants, automobiles and the trucks, those are the things that are big NO2 emitters," Lefer told ABC News.
Mulcahy said GASP has been monitoring the air quality in western Pennsylvania and found significant drops in sulfur dioxide, SO2, throughout March. At the beginning of March, the amount of SO2 in certain neighborhoods was around 0.055 parts per million (ppm). By the end of the month, it was under 0.01 ppm, according to the data.
Mulcahy noted that SO2 and other pollutants have been linked to higher rates of asthma, heart disease and other chronic diseases. A Harvard University study released earlier this month found that areas with increased air pollution could have higher rates of coronavirus infections.
Tune into ABC at 1 p.m. ET and ABC News Live at 4 p.m. ET every weekday for special coverage of the novel coronavirus with the full ABC News team, including the latest news, context and analysis.
Drew Shindell, a professor at Duke University's Nicholas School of the Environment, told ABC News that cleaner air can also provide some mental health relief during the pandemic.
In some cases, such as in China, India and the mountainous regions of the U.S., people have been able to see their horizons clearly for the first time in years without any smog.
"It can be apparent to people how [smog] is not natural and how much they can be in control of it," Shindell said.
He added that scientists have seen these drops in pollutants before. In 2008, air quality slightly improved in certain regions of the U.S. because of the global recession. During that year’s Summer Olympics, Beijing’s smog dissipated after the government implemented temporary air pollution controls, Shindell said.
The professor noted that the air quality in both of those incidences went back to their dirtier levels after the events ended, and it is highly likely that the same thing will happen whenever shelter-in-place orders are fully lifted.
"We don’t have an example of these changes leading to long-term benefits so far," he said.
While the social distancing orders will likely stay in place for weeks, environmentalists say people should find ways to take in the cleaner air where possible. Magavern, who lives in California, said that a few minutes outdoors, with proper social distancing from others, or even leaving the window open to catch some fresh air, would bring physical and mental health benefits.
"Of course [people] should be observing physical distancing, but go out and breathe the fresh air. Look at how beautiful our parks and cities and rural areas can be when the air is so clean. Remember that," he said.
What to know about Coronavirus:
Magavern and other environmentalists said they hope this newfound appreciation for clean air can lead to stronger policy actions by leaders. During a video news conference Thursday, former EPA administrator Gina McCarthy, who is now the chair of the Natural Resources Defense Council, said leaders needed to realize how important it is that they fight back against man-made pollutants.
"Maybe it'll be a wake-up call that public health and preparedness for public health is hugely important. It needs to be invested in," she said.
Charles Driscoll, a professor of environmental engineering at Syracuse University, fears that environmental policy may take a back seat in the coming months as governments focus on rebuilding the economy in a post-COVID-19 world. Nevertheless, he said there could be enough public demand to steer leaders to take action on the environment.
"I think hopefully people will see what the possibilities are and facilitate the transfer from fossil fuels to a renewable energy future," he told ABC News. "We really need federal leadership to get aboard on this."
ABC News' Stephanie Ebbs contributed to this report.