A Chinese court on Tuesday fined six companies in eastern Jiangsu province a total of 160 million yuan ($26 million) for releasing chemical waste into rivers, said state news agency Xinhua, the biggest fine of its kind ever handed out in China.

The firms in Taizhou city had discharged 25,000 tonnes of waste acid into two rivers, Xinhua reported late Tuesday, without identifying the companies.

The Jiangsu Provincial Higher People’s Court ordered the polluters to pay the fines into an environmental protection fund within 30 days.

Decades of rapid economic growth with little environmental oversight have brought major pollution problems for China’s air, soil and water. The government says around 70 percent of the nation’s rivers and lakes are polluted.

The court ruling comes just two days before a new environmental protection law enters into force that will give local authorities more power to punish violators.

Under the new law, penalty levels will be raised and polluters will risk prison for violating laws. They will also increase the number of institutions that can file lawsuits against polluters.

Over the past couple of years, Beijing has introduced a number of policies to halt the problem. But efforts to curb pollution are often ineffective because local environmental protection agencies lack the authority to implement rules and standards while maximum levels for environmental fines are low.

Investors are closely watching out for the impact of the new law on the steel and aluminum sectors, among the country’s biggest industrial polluters.