Woman walks with her child on a street as schools were closed due to the heavy smog in Jilin, northeast China's Jilin province.

A lawsuit filed by residents of a Chinese town against a chemical plant that they say is responsible for high levels of lead in the blood of local children is shaping up as a test of the central government's resolve to tackle pollution.

Of the more than 50 residents from in and around the rural town of Dapu in central Hunan province who originally agreed to join the lawsuit, only 11 remain, their lawyer, Dai Renhui, told Reuters. Hu Shaobo, another lawyer advising on the case, said some plaintiffs had withdrawn under pressure from local government officials.