They can do pretty decent damage to healthy adults too. I got attacked by a couple of larger dogs a few years ago (technically not pitbulls, but a related breed I'm not sure), had to get surgery and couldn't do my bullshit deskjob for like a month. Any physically intensive job and I would've needed 6 months off work. Considering what dicks employers are I wouldn't be surprised if there are people who end up homeless because someone forgot to close their backyard gate one day.