A new analysis by the Environmental Integrity Project (EIP) has found that the Clean Water Act, which was passed into law 50 years ago, has fallen short of its goals. The report found that nearly half of the rivers and streams across the US are considered too polluted to meet quality standards for swimming, recreation, aquatic life, fish consumption, or as drinking water sources.

More than 700,000 miles of waterways, about 51 percent of assessed river and stream miles, are impaired by pollution, in addition to another 55 percent of lake acres and 26 percent of estuary miles. Some states have done better than others, with Indiana, Oregon, and South Carolina topping the list of states with the dirtiest waterways.

EIP argues that this data does not provide the full extent of the nation’s water pollution as all states monitor their waterways differently, with no universal guidelines provided by the Environmental Protection Agency. The results come despite federal regulations mandated by the Clean Water Act of 1972, which has directed more than $1 trillion in investments into wastewater treatment plants and has driven substantial improvements in water quality.

The report outlined multiple ways the EPA could strengthen enforcement and modernize pollution solutions, including updating regulations for highly polluting industries and addressing agriculture runoff.