A new report says Maine’s coastal waters are in good shape compared with much of the rest of the country, but it gives low marks to the Northeast as a whole.

The U.S. Environmental Protection Agency this month released its National Coastal Conditions Report. The report said that tests for pollution, oxygen and other factors show the overall conditions of U.S. coastal waters is fair, the same rating given in a study four years ago.

Maine and other states are rated in regional groups, not individually. So while the report shows relatively clean test results along the Maine coast, the state is counted as part of the Northeast, which was ranked as one of the nation’s dirtiest coastal regions.

The problems in the Northeast are blamed primarily on urban runoff, sewage and other byproducts of the densely populated region between Boston and Maryland. Coastal experts say Maine’s conditions are better because there is less development, higher tides and colder waters.

But they also say Maine’s coast has its share of isolated problem areas, and that it is not immune to the threats that are plaguing other Northeast states.

“We only have to look that way to see what could happen as we grow,” said Lee Doggett of the Maine Department of Environmental Protection.

Maine, for example, may not have the same amount of runoff washing spilled motor oil or other pollutants into rivers and harbors as New York City does. But Maine gets more pollutants such as mercury out of the atmosphere, in the form of rain.

As development continues in Maine, especially near or along the coastline, the state is seeing more effects of storm runoff.

“There are spots where [Maine waters] are not meeting guidelines,” Doggett said. “In inner Portland Harbor, the animals living on the bottom are not in good shape” because of urban runoff, oil spills and other industrial activity, she said.

Joe Payne, bay-keeper for the Friends of Casco Bay, said the report doesn’t factor in the decline of coastal species, or show localized problems such as sewage outfalls that contaminate shellfish, Payne said.

“It would be unfortunate if people got comfortable that we have good coastal water quality,” he said. “We still have areas that are severely degraded that we need to work on.”