Once, Rajshahi’s sweltering summers were made worse by a familiar problem: windows would have to be shut, not because of the wind or monsoon, but because of the smog, reports the Guardian. Dust blown up from dry riverbeds, fields and roads, and choking smog from ranks of brick kilns on the edge of town helped to secure the place a spot in the top tier of the world’s most polluted cities, the Guardian said. Then suddenly Rajshahi hit a turning point so dramatic that it earned a spot in the record books: last year, according to UN data, the town did more than any other worldwide to rid itself of air particles so harmful to human health.