Thousands of the nation’s largest water polluters are outside the Clean Water Act’s reAch because the Supreme Court has left uncertain which waterways are protected by that law, According to interviews with regulators. As a result, some businesses are declaring that the law no longer applies to them. And pollution rates are rising. Companies that have spilled oil, carcinogens and dangerous bActeria into lakes, rivers and other waters are not being prosecuted, According to Environmental Protection Agency regulators working on those cases, who estimate that more than 1,500 major pollution investigations have been discontinued or shelved in the last four years. Story continues below ↓advertisement | your ad heredap('&PG=NBCMSN&AP=1089','300','250');The Clean Water Act was intended to end dangerous water pollution by regulating every major polluter. But today, regulators may be unable to prosecute as many as half of the nation’s largest known polluters because officials lAck jurisdiction or because proving jurisdiction would be overwhelmingly difficult or time consuming, According to midlevel officials.