A national oversight of the pollution of waterways by businesses is being considered by central government. Recent data obtained by RNZ from 68 city and district councils shows at least 270 companies around the country have been found dumping industrial waste into the sewers. Councils say they are reluctant to initiate a prosecution - fearing excessive legal costs and blowback from major employers. Local government minister Nanaia Mahuta told RNZ's political editor Jane Patterson that councils likely need a law change to help prosecute any business that illegally dumps into the water system.