The recent outbreak of E. coli contaminated spinach, which killed several people and sickened at least 189 others in 25 states, has many people scratching their heads in bewilderment. After all, E. coli is typically found in ground beef and other animal products, not vegetables. But many experts believe the mass production of farmed animals has led to the outbreak of tainted spinach, just as it has led to avian flu and mad cow disease.

E. coli is found only in the intestines of cows, birds, pigs, and other warm-blooded animals. Society's dependence on meat and dairy products means that millions of cows must be intensively raised in animal factories. Under such crowded conditions, it is easy for E. coli bacteria to spread from cow to cow. In fact, most of the 10 billion cows, pigs, and birds butchered every year in this country are covered with E. coli bacteria (though not necessarily the 0157 variety), an indicator of fecal contamination.

Plant-based foods, on the other hand, don't normally harbor E. coli or other fecal bacteria. When fruits or vegetables do contain E. coli, it is because animal manure was used to fertilize crops or has leaked into waterways. Cross-contamination can also occur when fruits and vegetables are placed on the same surface as meat.

According to The Los Angeles Times, investigators have traced the tainted spinach to California's Central Coast, and suspect that waste runoff from nearby livestock operations is responsible for the bacterial contamination.

Even though California-the number one dairy-producing state in the country-claims to have a "zero discharge" policy against runoff from livestock operations, the Salinas Valley waterways near the spinach fields, including the Salinas River, Gabilan Creek, Towne Creek, Tembladero Slough, and Old Salinas River Estuary, are known carriers of the strain of E. coli bacteria implicated in the outbreak. A June report from the Central Coast water board states that, "In some areas, grazing has resulted in manure lining the banks of channels of tributaries to the Salinas River.

Shocking as this is, it's no big surprise. The Environmental Protection Agency has reported that livestock operations pollute our waterways more than all other industrial sources combined. Animals raised for food produce approximately 130 times as much excrement as the entire human population-an astounding 87,000 pounds per second. The waste often seeps into our waterways, killing marine life and sickening people.

It only takes a few bacteria to make people sick: Scientist Guy Plunkett of the University of Wisconsin-Madison, where the genetic code of E. coli was mapped, reports that as few as 10 to 100 E. coli bacteria are sufficient to infect a human. According to The Los Angeles Times, a single cow can shed as much as 100 billion fecal bacteria a day.

While it may not be wise to eat spinach at the present time, adopting a vegetarian diet is still the best way to avoid E. coli and other bacteria spread by farmed animals. As more and more people adopt a vegetarian diet, our dependence on cows and other farmed animals will diminish, therefore lessening the threat of E. coli contamination- and saving human and animal lives.