The Buick Excelle GT, a close cousin of the U.S.-market Buick Verano, is a big seller in China -- but GM's sales streak could be threatened by tough new smog rules. Photo credit: General Motors Co.

Even during the company's descent into bankruptcy here in the U.S., China has been one of the brightest spots in General Motors' (NYSE:GM) global operations. Buick and Chevrolet are among China's best-selling car brands, and GM leads the market -- with solid growth in sales month after month.

But that growth streak could be in trouble -- and not because GM has stumbled. China's biggest cities have a growing smog problem, and the Chinese government is considering strict new limits on new-car sales in some areas. Meanwhile, GM is investing a fortune in hopes of even bigger growth in China in coming years. Will this prove to be an expensive mistake for the General?

In this video, contributor John Rosevear looks at what's going on in China's smoggy cities, and at the impact these proposed new rules could have on GM's growth plans in the world's largest auto market.