At one point, the workers in US slaughter houses were well paid and well respected. There were unions to look after their rights, and workers had safe working conditions and good medical care. This is no longer the case.
Unions no longer exist. Workers are recruited from across national borders, meaning that most are immigrants from impoverished countries, and an estimated quarter are in this country illegally. These immigrant workers are easier for the companies to control because many are illiterate not only in English, but in Spanish also. These workers are also willing to work for a much lower wage than non-immigrant workers. The companies keep the turnover rate high, so that most workers spend only a year working at a given slaughter house so that they are not employees long enough to be given medical insurance. When they are injured they are encouraged not to report the injury. This means that the companies can report a much lower incidence of injury than there actually is. And the number of injuries is high, because the companies keep the line speed high, and workers do not have time to clean and sharpen their knives and the speed at which they are forced to work means that they are unable to maintain enough control over their knives, leading to lacerations. In 1998, at least 29.3 percent of these workers were ill or injured, a number much higher than that for any other industry.
Source: Organic Consumers Association
