The informal term “factory farming” refers to any intensive commercial form of agriculture that employs extreme growing techniques (usually with heavy use of agrichemicals and veterinary drugs) to produce the greatest output in the least space, and at the lowest unit cost. Although the term occasionally refers also to intensive crop monocultures, for the purpose of this article it will refer exclusively to meat and dairy enterprises which meet the above criteria.
Not many people know of the severe environmental damage caused by factory farms. Concentrated animal waste from factory farms pollute the water and soil, cause dust and odour problems for people living in their vicinities, and are responsible for unacceptably high water usage.
Air Pollution
The manure mist that permeates the homes and skin of thousands of people who live near factory farms commonly contains dangerous levels of such noxious gases as hydrogen sulphide, ammonia and methane.
A citizen’s test in Renville County, Minnesota found that one-quarter of 32 tests taken near manure lagoons exceeded Minnesota air quality standards for hydrogen sulphide. This poisonous gas, usually associated with a “rotten egg” smell, causes symptoms such as nausea, headaches, blackout periods and vomiting. Although clouds of manure mist come and go with the wind, the odour itself sinks into human tissue, clothing and furnishings and is released slowly over time.
More at: http://www.all-creatures.org/articles/env-theimpact.html