Depends on whose hazelnuts you buy. I live in Oregon, which is a major world hazelnut producer, but our market is getting chipped away by Turkey - see the comment about Turkey and their practices. They're flooding the market and making it hard to be profitable domestically.
A friend who I went to kindergarten with, then roomed with in college, now does the engineering behind hazelnut harvesters (among other things) so I've ended up learning a few things. Domestic hazelnut production isn't awful on the scale of things. The trees don't use as much water as something like almonds, pesticide use tends to be lower than many crops, and mature orchards are relatively low maintenance (at least compared to fruit trees).
In terms of people, different orchards are going to have going to be better or worse than others in terms of who they hire and how they treat them of course, but on the scale of agriculture its generally less hard on the body than most. The harvesters my friends company makes drives up to the tree, extends and umbrella around it, then shakes the tree like a polaroid picture and that how the nuts are harvested.