With lockdowns underway in many parts of the world because of the COVID-19 pandemic, air quality has improved – in some places majorly. But the example of China shows that these improvements will likely be only temporary.
Strict and enforced lockdowns in Spain and India yielded the most visible drops in NO₂ levels in April compared to 2019, with improvements in air quality also traceable in the UK, the U.S., France, Spain and Mexico. NO₂ is a gas emitted by motor vehicles and factories mostly and is therefore a good indicator of human activity outside the home.
The most stunning difference was observed in Indian capital of New Delhi, normally one of the most polluted cities on Earth. Because a big chunk of Delhi’s pollution comes from relentless traffic, NO₂ levels dropped most noticeably here. Air pollution, which is most commonly measured by the concentration of PM2.5 (particles with a diameter of 2.5 μm or less), is made up by a combination of many factors – among them traffic, factories, natural events like storms or fires and cooking with solids.
In Wuhan, where the coronavirus originated and the outbreak is at a later stage, life started to gradually open up again in April, a fact that is starkly visible by NO₂ levels rising again to 2019 levels.