That was the key finding of the agency's first comprehensive examination of the health of U.S. waters.
Fifty-five percent of these waters were considered to be in "poor" condition for aquatic life, while just 21 percent of the waters were considered "good." The results were based on samples collected randomly from nearly 2,000 rivers during the summers of 2008 and 2009, the agency said.
Among the findings:
- More than a quarter of rivers and streams registered high nitrogen levels and 40 percent had too much phosphorous. Such nutrient pollution, which typically runs off of farmland, sparks algae growth, eroding food supplies and depriving aquatic species of oxygen.
- More than a quarter of rivers and streams are particularly prone to flooding, pollution and erosion because of a dearth of vegetation cover.
- Nine percent of waters tested positive for high bacteria levels, making them not fit for swimming.
- Fish in more than 13,000 of miles of water carried high levels of mercury, a toxic element particularly harmful to children and fetuses.
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