Pollution is often magnified because many animal factories are clustered together in one geographic area. In 1998, a 100,000-gallon spill into Minnesota's Beaver Creek killed close to 700,000 fish. Large-scale swine feedlots have been the biggest culprit of fish kills in Missouri, with 61 totaling more than 534,000 fish and affecting 150 miles of Missouri streams. A North Carolina study of nearly 1,600 wells adjacent to hog and poultry operations showed that ten percent of the wells tested were contaminated with nitrates above the drinking water standard, and 34 percent were contaminated with some level of nitrates. The air quality problems linked to animal factories include emissions of hydrogen sulfide, ammonia and methane.
Ammonia is a toxic form of nitrogen that causes algae blooms and fish kills in coastal waters.
Open-air lagoons, sprayfields and barns emit ammonia into the air and is deposited into waterways or fields about 50 miles away or more through fog or water. Drier airborne ammonia can travel hundreds of miles away. Methane is a potent greenhouse gas implicated in global climate change. EPA estimates that emissions from manure management were about 10 percent of total U.S. methane emissions. Of these emissions, liquid-based manure management systems such as those found in factory farms accounted for more than 80 percent of the total emissions from animal waste.