Across the U.S., air and vehicle traffic has dropped dramatically over the past several weeks as people stay inside and halt their daily routines to slow the spread of the coronavirus.

Air pollution has temporarily declined too. The northeastern U.S. has seen atmospheric levels of nitrogen dioxide air pollution drop by 30% in March compared with the same period last year, according to new satellite data from NASA's Goddard Space Flight Center.

It's the lowest monthly atmospheric nitrogen dioxide levels of any March during NASA's satellite data record beginning in 2005.

Nitrogen dioxide levels, which are influenced primarily by car and truck emissions and electricity production, have also declined over major polluting cities such as Seattle, Los Angeles, Atlanta, New York and Chicago.

Los Angeles, the traffic-congested city with some of the highest smog levels in the U.S., saw nitrogen levels drop significantly in the first two weeks of March, according to preliminary data from the European Space Agency's Sentinel-5P. The city's rush-hour traffic basically vanished after schools and businesses closed in March.

And researchers at Columbia University saw carbon monoxide emissions fall more than 50% below normal levels in New York City as a result of a plummet in vehicle traffic.

Nitrogen levels can fluctuate with natural variations in weather conditions, and researchers say that further analysis is needed to quantify the exact impact of the virus shutdown on air pollution levels.

However, scientists warn against celebrating any short-term benefits from the air pollution drop in the U.S. and across the world, since pollution levels will rebound once coronavirus restrictions are lifted.

Scientists also point out that longer-term exposure to air pollution has the biggest impact on people's health and a public health crisis is not a sustainable way to curb pollution.

The pandemic has already damaged the economy and overwhelmed the health-care system. Researchers warn it could also threaten long-term climate change progress by compromising global investments in clean energy and weakening industry environmental goals to reduce carbon dioxide emissions.