Experts say climate change must be addressed to combat worsening wildfire seasons.
"This is the most significant event in the past 50 years," said environmental health scientist Pablo Méndez Lázaro.
Some studies suggest that poor air quality could play a role in the severity of coronavirus.
The author's of the assessment say cleaner air is also responsible for fewer work absences and premature births.
"Poisoning our environment means poisoning our own body," said researcher Yaron Ogen.
Lockdown measures across the world have led to large decreases in vehicle traffic and industrial activity.
"The pandemic is a reminder that there is no separation between humans and the environment," researcher Karen O'Neill said.
"I have never seen aerosol values so low in the Indo-Gangetic Plain at this time of year," said NASA scientist Pawan Gupta.
Residents of the city of Jalandhar in Punjab have been posting images on social media showing the snow-capped peaks of the the Dhauladhar mountain range.
"Long-term exposure to air pollution increases vulnerability to experiencing the most severe COVID-19 outcomes," a team of Harvard scientists wrote.
"Air pollution levels as observed by satellite are showing drastic improvements in many areas that have been undergoing restrictive quarantines," researcher Peter DeCarlo told Newsweek.
In North America, air pollution wipes 1.4 years off people's lives on average, which could mostly be avoided if we stopped burning fossil fuels.
New research suggests current air pollution standards are failing to protect human health and life.
Pollution in New Delhi peaked this month, reaching levels not seen in three years. In some parts of the city, the Air Quality Index approached 1,000—more than three times what is considered hazardous.
Air quality levels are expected to reach unhealthy levels throughout the San Francisco Bay Area, and residents have been warned to avoid exposure.
Scientists looked at psychiatric children's hospital admissions in an Ohio city to investigate the link.
Exposure to air pollution has previously been linked to low birth weight and pre-term birth.
Scientists looked at data on millions of people to learn more about air pollution and mental health.
The researchers' conclusions are based on an 18-year study which involved over 7,000 subjects across six metropolitan areas in the United States.
Some 600,000 children were killed by air pollution in 2016.
Wildfires in British Columbia and California have blanketed the northwest U.S. in smoke, creating some of the most unhealthy air quality in the country.
New Delhi has the worst air quality in the world.
Researchers studied almost 131,000 people in London.
Air pollution causes 200,000 early deaths a year in the U.S. alone.