Unilad: [2] Satellite images from NASA show how levels of nitrogen dioxide have decreased across the Northeast region of the US, a region which includes the major cities of Washington, DC, New York City, Philadelphia and Boston. [3] These images reveal a 30% drop in March compared to the exact same period the year before, and are the lowest March levels on record since NASA began analysing data back in 2005.
[4] This decrease comes at a time of widespread isolation measures in the wake of the ongoing outbreak. Comparable changes in air pollution have recently been observed in other countries, including in parts of Italy and China. [5] Data from NASA’s Aura satellite works as an ‘effective proxy’ for nitrogen dioxide emission levels on the surface of our planet.
[6] However, as emphasised in the official statement from NASA, natural weather variations may also lead to changes in levels of pollution.

Therefore, these recent shifts could well be partly attributed to reduced emissions and partly to natural variations in the weather.