Runoff from pavement with coal-tar-based sealant is the most likely primary source of polycyclic aromatic hydrocarbons, or PAHs, found in the majority of streambed sediments of Great Lakes tributaries, according to a study published in Environmental Toxicology and Chemistry. PAHs are a group of chemicals found in crude oil and coal and occur as a byproduct of burning. PAHs can have harmful effects to organisms in the environment under certain conditions. So, it is important to understand their sources, distribution and magnitude in the Great Lakes Basin.
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Source: Phys.org