Metals In Boat Paints May Harm Life in Bay

There’s something foul about these anti-fouling boat paints.

A scientific study has concluded that anti-fouling boat paint is the likely source of copper pollution levels high enough to harm aquatic life in the Choptank River, a Chesapeake Bay tributary.

For centuries, copper-based paints have been applied to some boat hulls to protect them from barnacles and algae growth. But since the 1980s, the application has become even more common because U.S regulators restricted the use of another anti-fouling agent, called tributyltin (or TBT), which was found to be highly toxic.

But copper, a naturally-occurring element, can also be poisonous in certain concentrations and often leaches out of boat paints.

A report by David Whitall of the National Oceanic and Atmospheric Administration and colleagues, published in the journal Science of the Total Environment, found that the average copper levels in the lower Choptank River on Maryland’s Eastern Shore were at least four times higher than water quality standards meant to protect aquatic life. Some of the highest concentrations of copper were found not far from the marinas of Cambridge, Maryland.

"It surprised us. This was a wakeup call," said Thomas Fisher, a professor at the University of Maryland Center for Environmental Science and one of the co-authors of the report.  "I think (the copper) is coming from general boat traffic. Modern boat paints are designed to dissolve. That's how they work....We need to take a closer look at this, and see if there are some practices that could be addressed" to reduce the pollution, he said.

The report found that the copper levels exceeded EPA acute water quality standards in 64 percent of the samples analyzed. These are levels at which some aquatic life will die when exposed in a lab test. “These data indicate that copper exposure especially in the lower Choptank estuary may be problematic for aquatic species,” the report states.

The researchers discovered that the copper levels were not high upstream, near agricultural areas -– suggesting that farming was not the source of the metal.  (A form of the metal, copper sulfate, is sometimes used to kill algal blooms in farm ponds).  But the metal concentrations were high downstream, in an area where there are several marinas and lots of boats, according to the report.

The scientists also looked at a variety of other pollutants in the river –- including nitrates and phosphorus -–- and concluded that farmland and wastewater treatment plants were the likely sources of these pollutants.

It's not clear how the copper might be moving from boats into the water. While some anti-fouling paints are designed to slowly dissolve over time, boat maintenance yards also scrape the paints off, and in some cases may not be following practices to keep the particles out of the water. "We don't know any of those details," said Fisher.

Are you a boater who uses anti-fouling paint? What do you think about this? 

After I asked these questions in my August 23, 2010, article, a reader wrote in the next day suggesting that the copper in car brake pads might be a source of the metal in the Choptank River, with the dust from the grinding of brakes perhaps carried into the waterway as rain washed over parking lots and roads. An earlier study in the San Francisco Bay area suggested such a link.

On August 24, I asked one of the authors of the Choptank River study, Cathleen Hapeman, research chemist with the U.S.D.A. agricultural research service in Beltsville, about the possibility of a link to car brakes.  Hapeman said: "that's an interesting possibility. We could take a look at that." But she noted that  while one of the monitoring stations that found high copper levels was near places with lots of cars and trucks -- Cambridge and the Route 50 bridge -- the other two stations that found lots of copper were in more rural locations without as many vehicles. Meanwhile, all three locations with significant amounts of copper had large amounts of boat traffic.

Hapeman also passed along a 1987 study, by W. Scott Hall of Johns Hopkins University and colleagues, that found elevated copper levels at five locations around the Chesapeake Bay (including near Cambridge, Baltimore and Annapolis) and also suggested a connection to anti-fouling boat paint.  Since the time of the 1987 study, the concentrations of copper in the Choptank River's waters have risen, Hapeman said, suggesting that the continued use of anti-fouling paint over the decades could be adding more potentially toxic metal to the waterway. She cautioned, however, that it still is not clear what the source of the copper is, and boat paint is only viewed as one likely source.

Comments

[Chuck]

Interesting. Wonder how well they looked at other potential sources. In San Francisco Bay, the leading source of copper was urban runoff associated with automobile brake linings.

[Tom Pelton]

Thanks for that very well-informed comment, Chuck. There are certainly both marinas and parking lots in Cambridge, Maryland, and maybe both boats and cars contributed to the pollution. It's a question that deserves more research.

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[Boat Wax]

Interesting article. Definitely something to watch out for and consider when a paint job is needed. Thanks for the post!

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