CHICAGO (WBBM Newsradio) – More than 6,400 oil spills were reported across the Great Lakes and their connecting waters over a decade, but gaps in reporting make their environmental effects difficult to assess, according to a new study.
Researchers led by Lake Superior State University reviewed U.S. and Canadian records from 2015 through 2024 and identified 6,453 incidents. The findings were published in the Journal of Great Lakes Research.
Most incidents involved smaller releases. Although large spills accounted for most of the reported oil volume, many smaller spills lacked information about the amount or type of oil released.
Lake Michigan had the most reported spills of any Great Lake, averaging about 150 annually. Connecting waterways, including the St. Clair and Detroit rivers, had higher spill densities than the open lakes.
Only about 35% of U.S. incident reports included spill volumes, while Canadian records lacked volume information before 2023. Shipping-related incidents were the most common in U.S. waters; facility-related spills were most common in Canada.
Researchers say the ecological effects of frequent, smaller spills remain largely unstudied. They called for more consistent reporting between the two countries to improve understanding of risks to freshwater ecosystems.
