COLUMBUS (AP) — A commission monitoring pollution in the Ohio River says testing for mercury released into the water will be determined on a state-by-state basis rather than a comprehensive plan.

The multistate Ohio River Valley Water Sanitation Commission decided Thursday that states along the waterway will decide where and how companies do testing to gauge discharged mercury, The Columbus Dispatch reported.

The panel’s decision in effect nixed a 2003 commission ruling to force companies to test for mercury at discharge pipes, where the concentration would be the highest. This month was the deadline for companies to comply with the 2003 ruling.

But the commission gave assurances Thursday that the decision won’t result in increasing levels of mercury, a neurotoxin, in the river and its tributaries. Environmental advocates disagreed.

“I think it leaves the door open for there to be more mercury going in,” said Madeline Fleisher, an Ohio-based lawyer with the Environmental Law and Poverty Center.

Mercury has been pumped into the water for years from steel factories, coal-fired power plants and other sources, and can make fish unsafe to eat. The amounts of mercury released are subject to regulatory limits based on tests by the companies, which sometimes do their testing in places where pollution is diluted.

Some states along the waterway, including Ohio, give permission to companies to exceed the federally regulated mercury dumping limit.

“We’re not going to clean up the entire river tomorrow, but you have to take steps in the right direction, and I don’t think this is in the right direction,” Fleisher said. “At the very least, it’s standing still when we should be moving forward.”