Great Atlantic Smog Storm
From Tardis Wiki, the free Doctor Who reference
The Great Atlantic Smog Storm was a powerful storm that raged on Earth from roughly 200080 to at least 200100. There were regular news flashes telling the population when it was safe to breathe outside. (TV: Bad Wolf)
According to Doctor Who: Time Traveller's Almanac, The Great Atlantic Smog Storm was caused by planet-wide pollution becoming so bad.