When I was a boy my brother and I's job during school summer holidays was to strap motorized backpack sprayers onto our backs and spray woody weeds with a nasty chemical called 245T.
It was hot work especially hanging off steep cliff like slopes, so we would wear tanktops and shorts. The 245T spray would constantly dribble from the leaky tank caps and mixed with our sweat, would trickle down our backs, which helped keep us cool. It was hard to know whether the night time headaches were heatstroke or simple poisoning. Good times!