on methane emissions, antibiotic resistance, and climate change, and thus, recommends eliminating environmental stressors and modifying feeding strategies, including sources of feed grain, amount of forage, and amount of digestible nutrients as strategies for reducing emissions. The Humane Society of the United States (HSUS) advocates for minimizing the use of non-therapeutic antibiotics, especially those that are widely used in human medicine, at the advice of over 350 organizations including the American Medical Association. If no change is made and methane emissions continue increasing in direct proportion to the number of livestock, global methane production is predicted to increase 60% by 2030. Greenhouse gases and climate change affect the air quality with adverse health effects including respiratory disorders, lung tissue damage, and allergies. Reducing the increase of greenhouse gas emissions from livestock could rapidly curb global warming. In addition, people who live near CAFOs frequently complain of the odors, which come from a complex mixture of ammonia, hydrogen sulfide, carbon dioxide, and volatile and semi-volatile organic compounds. In regard to air quality effects caused by waste disposal, some CAFOs will use "spray fields" and pump the waste of thousands of animals into a machine that sprays it onto an open field. The spray can be carried by wind onto nearby homes, depositing pathogens, heavy metals, and antibiotic resistant bacteria into the air of communities often consisting mostly of low income and/or racial minority families. The odor plume caused by emissions and spraying often pervades nearby communities, contains respiratory and eye irritants including hydrogen sulfide and ammonia. Economic impact Increased role in the market The economic role of CAFOs has expanded significantly in the U.S. in the past few decades, and there is clear evidence that CAFOs have come to dominate animal production industries. The rise in large-scale animal agriculture began in the 1930s with the modern mechanization of swine slaughterhouse operations. The growth of corporate contracting has also contributed to a transition from a system of many small-scale farms to one of relatively few large industrial-scale farms. This has dramatically changed the animal agricultural sector in the United States. According to the National Agricultural Statistics Service, "In the 1930s, there were close to 7 million farms in the United States and as of the 2002 census, just over 2 million farms remain." From 1969 to 2002, the number of family farms dropped by 39%, yet the percentage of family farms has