You may have to supervise at construction sites, and those are dangerous places. A construction worker may fall on you from ten stories. And most of them are hefty, donut-totin' union fellows.
But for the most part, danger is not a physical threat in this gig. You may be hunched over a drafting table, which could mean back pain, but more likely you will be doing your designing on a computer, in which case you will instead be hunched over a computer monitor, meaning a lesser degree of back pain. And then, of course, there are the usual eye strain and carpal tunnel hazards, but you're not going to need your eyes or hands in 50-60 years anyway.