Nearly all of the toxic pollutants in Maryland's waterways come from the watershed that enters the Chesapeake Bay near Baltimore, according to a report released Thursday by an environmental watchdog group.

The Gunpowder-Patapsco Watershed, which stretches above the Maryland-Pennsylvania border and as far west as Mount Airy, had more than 1.3 million pounds of toxins dumped into it during 2010, the nonprofit group Environment Maryland concluded.

That's 98 percent of the chemicals released into the state's waterways that year, the report said. The watershed is the 43rd most polluted in the country.

Curtis Creek, south of Brooklyn along the border of Baltimore and Anne Arundel County, received the vast majority of those pollutants, the group's study said. About 922,000 pounds of chemicals were released into the creek, which feeds into Curtis Bay.

The report, which has a national scope, said that 26 million pounds of chemicals find their way into the 1,400 U.S. waterways during 2010.

The chemicals, which have been linked to cancer, developmental and reproductive disorders, include mercury, arsenic and benzene.

Environment Maryland analyzed data from the U.S. Environmental Protection Agency's Toxic Release Inventory for 2010. It is the most recent data available, Environment Maryland said.

The full report is available online.