What's in Washington's water?

I paddle my touring kayak in the Potomac but never a whitewater kayak - never have wanted to practice self-rescues and rolls in that water. Okay, I know, there are world champion kayakers here in DC, and they do it all the time, but they also run the class 5+ rapids at Great Falls. Go figure. My aversion to doing face plants in the majestic river arises from my son's fifth-grade science fair project on water pollution in Washington D.C. We were both shocked to learn that towards the end of the 19th century, some genius designed the sewer system of the nation's capital to handle rain by overflowing straight into the Potomac. Saber the golden retriever provided valuable confirmation every time she chased a duck and straggled back to shore smelling like a cesspool. Last week, the U.S. Geological Service published considerably more sophisticated - and chilling - scientific studies of man-made chemicals polluting the Potomac and eight other major rivers. U.S.G.S. researchers found 85 chemicals in samples taken from the Potomac between 2003 and 2005. Among them: water treatment by-products chloroform and bromodichloromethane, a suspected human carcinogen, gasoline hydrocarbons and related chemicals, a dozen herbicides, three pesticides, a fungicide, four manufacturing additives, five cosmetics chemicals, an industrial solvent, cholesterol and two other plant or animal-derived biochemicals. One of the herbicides detected was atrazine, a notorious weed killer suspected of causing the Potomac's "intersex" bass - males that have produced eggs. A USGS report focusing on tap water derived from the Potomac found that two thirds of 26 compounds detected in at least a fifth of the samples from the great river also showed up in tap water produced for Washington and northern Virginia. The report cautioned that "concentrations for all detected compounds in source and finished water generally were less than 0.1 microgram per liter and always less than human-health benchmarks...On the basis of this screening-level assessment, adverse effects to human health are expected to be negligible (subject to limitations of available human-health benchmarks)."