The manufacturing industry is built on a sub culture of drugs and alcohol. It's amazing the number of guys who immediately smoke a one-hitter or start getting drunk before their cars are even out of the parking lot after work. Hell, they often start over lunch. Every day! If the manufacturing sector ever actually started to enforce drug policies, they'd lose 3/4ths of their employees. Many of whom actually do their jobs quite well. And this includes managers and foremen.
Yep, that was my experience way back when when I worked at 3M Sandpaper, Bournes Plastics and with FoxxConn.