DETROIT (AP) - Tests by the Michigan Department of Environmental Quality have found that hulking black mounds along the banks of the Detroit River in southwest Detroit don't pose a threat to human health.
The petroleum coke, or pet coke, mounds are a byproduct of oil refining used in energy production. The material has been brought by trucks from the nearby Marathon Petroleum Co. refinery, and the mounds drew attention starting earlier this year.
The Detroit News reported the MDEQ's findings Friday.
Area residents, the Canadian government and U.S. lawmakers are among those concerned about potential pollution and health effects.
Findlay, Ohio-based Marathon Petroleum says the pet coke stored along the Detroit River is no longer owned by the company. If stored properly, however, Marathon says pet coke poses no environmental concerns.