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... Iowa has a long-simmering water problem that has finally begun to boil over " and it's changing Iowa politics. People are angry and worried about the quality of the state's water, the health risks it poses and its increasingly undeniable tie to the state's signature industry: agriculture.

In recent years, Iowa's cancer rate has climbed significantly above the U.S. average. It now stands as the nation's second highest, and Iowa is one of only three states where the rate is rising.

The situation has put a spotlight on nitrates, which are linked to a growing body of science to kidney, brain and ovarian cancer.

Nitrates are a key component in the deluge of chemical pesticides and fertilizers used by the state's farmers, some of which washes off farm fields and into waterways.

A second culprit is glyphosate, the active ingredient in Roundup, the world's most common weedkiller, which the International Agency for Research on Cancer declared "probably carcinogenic" in 2015, an assessment rejected by the U.S. Environmental Protection Agency. ...