There was at least one mishap during Apollo capsule reentry where astronauts were exposed to fumes from hypergolic fuel, after forgetting to purge the thrusters at the proper time: https://en.wikipedia.org/wiki/Apollo%E2%80%93Soyuz_Test_Proj...

That brief exposure, before they got their oxygen masks on, put them in the hospital for a couple of weeks. It really could have been worse.

I believe the technical procedure for unprotected ground crew dealing with a leak of this stuff is, roughly, "turn around and run for your life." Hence the guys in funny-looking suits.