The oyster population is in peril in Maryland with only 0.3% of its 19th century population remaining. 1 This is due to a variety of factors including water pollution from numerous sources. The desire to save this species is so great that the State of Maryland is encouraging private dock owners to assist in the re-population of oysters by attaching juvenile to their docks to increase survival.
The researchers focused on the pollutant polycyclic aromatic hydrocarbons, or PAH's. PAH's are the potent problem chemical family in coal tar sealants which have been banned in numerous locations around the US. This particular study looked at roadways, not parking lots. Roadways rarely are treated with coal tar, but it is very frequent on parking lots. It would have been an interesting line of research if they had looked at specific parking lot runoff, but perhaps that could be for a future study. It also would be good to know just how much of that PAH was transported there from coal tar sealed parking lots. The USGS has observed this phenomenon in several locations across the US.
The concentration of PAH's used in the study were based upon the researchers' previous work with local roadway runoff. The PAH concentration was within an order of magnitude of the probable biological effects concentration of 23 ppm.
The study's concluding findings are worth quoting:
This study's results provide evidence that PAHs entering an aquatic ecosystem from runoff from road surfaces have the potential to inhibit oyster reproduction by negatively impacting three critical processes in the early life cycle of the Eastern oyster.
The mystery to me is that with this knowledge and the value of this resource to the people of Maryland (and the Nation), that the practice of coal tar sealant use on parking lots continues. The EPA led a Chesapeake Bay Toxic's Task Force that took topic up over 4 years ago and was ineffective in even recommending that the product use be curtailed. Let's hope that coal tar sealer legislation pending in Montgomery County Maryland can begin this change for the State.