transfer of pathogens through drinking water contamination can lead to widespread outbreaks of illness. The EPA estimates that about 53% of people in the United States rely on groundwater resources for drinking water. There are numerous effects on human health due to water contaminated by CAFOs. Accidental ingestion of contaminated water can result in diarrhea or other gastrointestinal illnesses and dermal exposure can result in irritation and infection of the skin, eyes or ear. High levels of nitrate also pose a threat to high-risk populations such as young children, pregnant women or the elderly. Several studies have shown that high levels of nitrate in drinking water are associated with increased risk of hyperthyroidism, insulin dependent diabetes and central nervous system malformations. The exposure to chemical contaminates, such as antibiotics, in drinking water also creates problems for public health. In order to maximize animal production, CAFOs have used an increasing number of antibiotics, which in turn, increases bacterial resistance. This resistance threatens the efficiency of medical treatment for humans fighting bacterial infections. Contaminated surface and groundwater is especially concerning, due to its role as a pathway for the dissemination of antibiotic resistant bacteria. Due to the various antibiotics and pharmaceutical drugs found at a high density in contaminated water, antibiotic resistance can result due to DNA mutations, transformations and conjugations. Antibiotics are used heavily in CAFOs to both treat and prevent illness in individual animals as well as groups. The close quarters inside CAFOs promote the sharing of pathogens between animals and thus, the rapid spread of disease. Even if their stock are not sick, CAFOs will incorporate low doses of antibiotics into feed "to reduce the chance for infection and to eliminate the need for animals to expend energy fighting off bacteria, with the assumption that saved energy will be translated into growth". This practice is an example of a non-therapeutic use of antibiotics. Such antibiotic use is thought to allow animals to grow faster and bigger, consequently maximizing production for that CAFO. Regardless, the World Health Organization has recommended that the non-therapeutic use of antibiotics in animal husbandry be reevaluated, as it contributes to the overuse of antibiotics and thus the emergence of resistant bacteria that can spread to humans. When bacteria naturally occurring in the animals' environment and/or body are exposed to antibiotics, natural selection results in bacteria, who have genetic variations that protect them from the drugs,