Killing for a Living: Psychological and Physiological Effects of Alienation of Food Production on Slaughterhouse Workers - https://core.ac.uk/outputs/54847380
Additionally, Upton Sinclair who wrote The Jungle, which is largely attributed with launching public pressure to create federal reforms for more sanitary meat packing, originally created this to highlight how it fucked up the workers: https://en.wikipedia.org/wiki/The_Jungle