Here is a really good Time Mag. article :
When the pig is slaughtered, at about 5 months of age, he'll become sausage or bacon that will sell cheap, feeding an American addiction to meat that has contributed to an obesity epidemic currently afflicting more than two-thirds of the population. And when the rains come, the excess fertilizer that coaxed so much corn from the ground will be washed into the Mississippi River and down into the Gulf of Mexico, where it will help kill fish for miles and miles around. That's the state of your bacon — circa 2009.