Environmental scientists and social activists are beginning to argue that caged animal feeding operations (CAFOs) are harmful to the environment in various ways. CAFOs are the result of 10,000 years of human progress stemming from the transition from a hunter-gatherer society to an agrarian society. The transition from a hunter-gatherer society to an agrarian society contributed to the creation of large cities, resulting in higher populations, such as Mesopotamia. As time passed and countries began to become more populated, especially the United States, a higher demand for food had to be met due to the growing population. It got to the point where there were so many people that small family farms could no longer meet the demand of a growing population. The advent of new technologies such as the automobile, refrigerator, food processing and preservation have provided entrepreneurs with a way to get started. new businesses that enabled large-scale production, distribution, and retailing of meat and plant-based foods. The result is CAFOs. CAFOs are beneficial in that they can provide a low-cost source of meat, milk and eggs through efficient animal feeding and watering methods, as well as boost the local economy by creating jobs. Unfortunately, the disadvantages of CAFOs far outweigh the advantages. The most pressing problem associated with CAFOs comes from the amount of manure/waste they produce. Manure resulting from CAFOs contains a range of potential contaminants. Manure is full of plant nutrients such as nitrogen and phosphorus, pathogens such as E.coli, growth hormones, antibiotics, chemicals used as additives to manure or to clean the equipment, animal blood, silage...... middle of paper ......urkholder, J., Libra, B., Weyer, P., Heathcote, S., Kolpin, D., Thorne , P. et al. (2007). Impacts of waste from concentrated animal feeding operations on water quality. Environmental Health Perspectives, 11(2), 308-312. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1817674/pdf/ehp0115-000308.pdf Hribar, Carrie, MA. Understand concentrated animal feeding operations and their impact on communities. Ed. Mark Schultz, MD http://www.cdc.gov/nceh/ehs/docs/understanding_cafos_nalboh.pdf. National Association of Local Boards of Health, nd Web. December 14, 2013. .Sigurdarson, ST & Kline, JN (2006). School proximity to concentrated animal feeding operations and prevalence of asthma among students. Chest, 129, 1486-1491. Retrieved from http://chestjournal.chestpubs.org/content/129/6/1486.full.pdf