A River Runs Through It

What goes down the drain eventually bubbles up in rivers and streams, according to a U.S. Geological Survey report on 140 waterways in 30 states. The stuff comes from farms and factories, as well as toilets, sinks and medicine chests. Environmentalists fear that even trace amounts of some pollutants might increase resistance to antibiotics, disrupt reproductive cycles or act as carcinogens. But in most cases, scientists don't know enough about exposure to contaminants at minute quantities to say what dangers, if any, they pose. Among the 95 chemicals tracked:

Insect repellents
Found in 74% of samples; 1.1 p.p.b.*

Caffeine
Found in 70% of samples; 6.0 p.p.b.

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Antibiotics
Found in 48% of samples; 3.6 p.p.b.

Reproductive hormones
Found in 40% of samples; 2.0 p.p.b.

Prescription drugs
Found in 32% of samples; 1.8 p.p.b.

Fragrances
Found in 27% of samples; 4.3 p.p.b.

*parts per billion