Re: Health and Safety
It is health and safety, in that hot water must be stored above 60°C in order to pasteurise it.
On the other hand it's not health and safety, because you shouldn't have water coming out of taps at more than 45°C.
I think the lack of mixer taps in the past is a legacy of people putting the plug into the sink, and filling it up to wash their hands in. Whereas there are often no plugs now, because most people wash hands under running taps.
So we now use more mixer taps, or TMVs (thermostatic mixing valves) on the hot.
However, if you want to kill germs on your hands in the few seconds they're under the hot tap, then you'd need to do it under water that was above 65-70°C. Even at 60°C, if memory serves, it takes a minute or two to kill the bugs. Don't try this at home though - unless you fancy serious burns. From memory, again, it takes about a minute to get burnt at 50°C, but only a second at 60°C.
That's why we use soap, which is what's actually doing the cleaning. The warm water is only there to make it feel nicer.