India is home to some of the most polluted cities in the world.

When India imposed a countrywide lockdown on March 25, 2020, it encompassed 1.3 billion people, making it the world's largest lockdown.

With all those people at home, factories closed, air traffic down, and fewer cars and buses on the road, air pollution has visibly decreased.

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India has long struggled with pollution. In fact, according to the World Economic Forum, in February, India was home to six out of 10 of the world's most polluted cities.

On March 25, when India ordered a since-extended 21-day lockdown amid the spread of the coronavirus pandemic, it created the world's largest lockdown, encompassing 1.3 billion people.

With that many people home, traffic is virtually nonexistent, factories are closed, and construction has come to a halt, leading to a noticeable reduction in smog and air pollution.

While the environment may be convalescing during the pandemic, experts don't think this will last. But, in the meantime, the short-term effects are pretty striking, as these before-and-after pictures show.