When did air pollution start in linfen china?

Air pollution in Linfen, China, began to escalate significantly in the late 20th century, particularly during the rapid industrialization of the 1990s. The city's heavy reliance on coal mining and processing, along with lax environmental regulations, contributed to severe air quality issues. By the early 2000s, Linfen was often cited as one of the most polluted cities in the world, prompting national and international attention to its environmental challenges.