Everybody knows pigs smell. Not everyone though, knows how that smell can affect human health. Yet more and more people are being exposed to it. The old farms of a few dozen hogs are fast giving way to mega-farms. Forty percent of all hogs in the United States are produced on farms with at least fifty-thousand head. And more animals means more manure which concerns environmentalists and neighbors of these animal cities. In the first of a two-part series, the Great Lakes Radio Consortium’s Dan Gorenstein reports. not only is there a threat to water sources from runoff and contamination, but the stockpiles of waste release bad-smelling emissions and chemicals into the air: