"Since 2004, the state has allowed 42 treatment facilities, power plants and factories to ignore federal limits on dumping mercury into lakes, rivers and streams.
This year, the Ohio Environmental Protection Agency is considering more than 30 new requests for variances from companies that argue that the cost of keeping mercury out of the water far exceeds any benefits to wildlife and human health.
Some argue that the technology needed to meet the limits set in 1995 does not exist.
"There is no treatment technology available to get to these low levels," said Pat Hemlepp, a spokesman for Columbus-based American Electric Power.
But critics say governments are doing little, if anything, to make businesses develop cheap, reliable filters to remove mercury."