In order to counter the stress and disease experienced by these animals, drugs are routinely administered. Drugs are also commonly used for growth promotion. Due to the high levels of antibiotics and other contaminants in commercially sold meat, factory farms are creating a serious food safety risks. Many scientists are concerned that the overuse of antibiotics in animals is linked to new strains of bacteria that are resistant to antibiotics. Phosphorus and nitrogen from manure cause major surface water pollution problems.
Manure decreases the oxygen in the water and as a result, the fish suffocate.
Nutrients from manure also harm marine life by creating noxious algae. Also linked to nutrient pollution, is the highly publicized organism pfiesteria piscicida. The pathogens contained in animal waste have contaminated the drinking water supply and caused gastrointestinal illnesses and even death. Soil Pollution Soil contamination is another form of pollution caused by animal waste from factory farms. Heavy metals such as zinc and copper are added to animal feed and end up in the soil after lagoon spills and when excessive manure is applied to crops.