Northwest China's Xinjiang Uygur Autonomous Region has issued new standards to limit pollutant discharge from mineral firms.
The new standards will be applied to companies in minerals, electroplating and battery manufacture in Fuyun, Shache and Shanshan counties, according to Xinjiang's environmental protection agency.
The companies must immediately implement the new standards in new or expanded projects.
Ongoing or approved projects will be subject to the new standards from April 1, 2019.
Xinjiang, heavily reliant on energy resource exploitation, still faces many environmental issues, such as insufficient cuts to production capacity, and inadequate treatment of air and water pollution.
Some cities, including the regional capital Urumqi, have seen their air quality deteriorating over the past few years.