Things I Won’t Work With: Peroxide Peroxides (2014)
There are things that we shouln't work with, but we do because we don't know the associated risk, some examples:  -maintenance of your DOT4 brakes? do not touch the DOT4
   brake fuild, it's absorbed though your skin and it will
   kill your kidneys when they try to filter it.
  -Old house in america? check you don't have any pipe 
   soldered with lead, hot water will eventually make it 
   evaporate
  -lead in electrical solder wire
  -mercury, a powerful neuro-toxin

Edit:  -again, old house, check to change the paint, yep, lead
   in the pain again.
  -close to an airport? beside noise, lead in the airplanes 
   fuel
  -Teflon... again Dupont and 3M
  -Aluminum on cookware... toxic

lead was one of the technical debts introduced by a guy (1)... the same guy who introduce it to the fuel making a generation at least 10 iq point less smart.... and created the CFCs in aerosol... Dupont, GM and others did a lot of money on that.... as always.(1) https://en.wikipedia.org/wiki/Thomas_Midgley,_Jr.