SHANGHAI (Reuters) – China’s environmental crackdown is the “biggest uncertainty” facing the nation’s copper smelters, as the government steps up inspections and stiffens emissions control standards, an executive from Jiangxi Copper Co Ltd said on Wednesday.

“Producers risk being shut down. Supervision teams are everywhere,” Yuneng Wu, vice president of the state-owned company, which is the country’s top integrated copper producer, said at the Asia Copper Conference in Shanghai.