Burning coal in a power plant creates byproducts called fly ash and bottom ash.  That ash contains a lot of bad stuff - mercury, lead, arsenic, to name a few.

While some plants ship the dry ash to landfills that accept hazardous materials, others mix the ash with water to make a slurry, which is moved into holding ponds.

Eventually, the water in those ponds is released into the nearest waterway.

The U.S. Environmental Protection Agency acknowledges that the slurries from coal-fired plants account for more than half the toxic pollutants dumped into U.S. waters by regulated industries.

GRAND RAPIDS, Mich. (AP) - Officials say about 150 people who were evacuated from homes in Kent County because of flooding have been allowed to return home.

Kent County spokeswoman Lisa LaPlante says those allowed home by around midday Wednesday are among nearly 700 officials believe are evacuated. She says officials want to make sure homes are inspected before people return and utility crews restore power and natural gas service.

The Kent County number doesn't include about 1,000 people evacuated from downtown Grand Rapids' Plaza Towers because of the rain-swollen Grand River.

LaPlante says it could be weeks before Kent County officials have estimates of the financial cost of the flooding damage in the area.

Air quality is improving in some Michigan cities, according to a new report. The American Lung Association’s annual ‘State of the Air’ report is out today.  

Jim Harrington is a field organizer for the American Lung Association. He says particulate pollution, like smog, is down in the region - including the cities of Flint and Detroit.

“In prior years they’d been ranked the worst in the country. They were one of the most polluted regions in the country,” says Harrington, “And over the last five years, they’ve gradually moved down the list. So they’ve been improving at a faster rate than other areas.”