Will the de-fogging agent for snorkeling/scuba goggles prevent or mitigate steaming up of safety glasses worn outside on a hot, humid day?
Defogging a dive mask is usually done with a soap solution. You get two effects that help keep moisture from forming on the glass: cleaning and a soap residue. Baby shampoo works for me, is cheaper than specially branded mask defogger, and smells baby fresh to boot. I've used it on my prescription lenses and on sunglasses. I haven't actually used it on safety glasses. (I do my woodworking inside.) But I know of no reason why cleaning your safety glasses with mild soap like baby shampoo will harm them. So it should be really easy for you to test in your current, sweaty environment.