DES MOINES – Iowa is one of the last states in the nation to protect rivers, lakes and streams as required by the 1972 federal Clean Water Act, and pollution opponents are still fighting for change.

The Environmental Protection Commission ended eight years of debate in January by approving limits on water pollutants. The rules are aimed at bacteria, which can threaten the health of humans and animals, and ammonia, which harms fish and aquatic plants.

But state lawmakers could still block any changes. For more than three decades, political opposition and cost concerns have kept Iowa from complying with clean water requirements.

If that continues, groups such as the Iowa Environmental Council are likely to sue and demand that federal law be enforced. Judges have consistently backed stricter limits on water pollutants in similar cases.

“To my knowledge, there is no state that is out of compliance like Iowa is,” said Albert Ettinger, a Chicago lawyer representing Iowa environmental groups.

The Clean Water Act requires that rivers be protected for recreation and aquatic life, unless studies prove that would be impossible.

Since the law was enacted in 1972, Iowa has lagged behind the rest of the nation. City officials have pressured state lawmakers against making changes because of the high costs that would be involved.

To properly reduce ammonia and bacteria, many cities would have to build new sewage plants that could cost hundreds of millions of dollars. Some officials have claimed that most of Iowa’s pollution comes from farms, not cities.

The state Department of Natural Resources estimates that 1,500 sewage treatment plants in cities and industrial plants across Iowa must improve or at least change their operations to meet the rules. Many Iowans could see their water and sewer bills go up $35 to $40 a month.

Iowa didn’t get federal money for expensive sewer projects, as some states did in the 1970s, because it didn’t set required water quality standards, Ettinger said.

“Iowa basically missed the gravy train,” he said. “I have no idea what they were thinking in Iowa.”