Decisive action is needed to address PAHs (polycyclic aromatic hydrocarbons) from coal tar pavement sealants and other contaminants of concern in the Mississippi River according to a recently published report. These are part of the problems found in the section of the River running through the Minneapolis metropolitan area by a joint effort by the National Parks Service and the Friends of the Mississippi River.
Additional contaminants, including PAHs, PDBEs, pharmaceuticals, and endocrine disrupting compounds, may also negatively impact the ecological health of the Mississippi River, and raise public health concerns as well.
PAHs and coal tar sealants. PAHs (polycyclic aromatic hydrocarbons) are a group of compounds that can cause tumors, organ abnormalities, and disrupt immune and reproductive system function in fish and aquatic life. Seven PAH compounds are classified as probable human carcinogens. Coal tar sealants (coal by-products used to seal asphalt surfaces since the 1960s) are a major source of PAH pollution. PAH concentrations in coal tar sealants are about 1000 times higher than concentrations in asphalt-based sealant alternatives.
Over time, the sealants wear down and are carried into the environment by wind and rain, allowing PAHs to contaminate rivers, lakes, wetlands, and stormwater ponds. While little is known about PAH contamination in Mississippi River sediment, projected clean up costs for stormwater ponds contaminated with PAH runoff could approach $1 to $5 billion in the Twin Cities metropolitan area alone. As of August 2012, 24 Minnesota communities have coal tar sealant restrictions of some kind, and the State has its own restrictions for state agencies. For more information on coal tar sealants, contact the Minnesota Pollution Control Agency.
And emerging contaminants, like triclosan, PAH compounds, and others present risks to the river that we do not yet fully understand. The solutions to these problems require new tools and decisive public action before they move beyond our reach.