If your house was built in the 50's and has copper pipe with soldered joints, odds are excellent that your water contains significant amounts of lead in it.  Odds are also good that you have layers of paint with it too.  Any amount of lead has neuro-development issues in children, affecting their IQ's as well as other health effects.  Ben Franklin didn't know that, and it wasn't well documented until research in the 70's and beyond.

You likely have asbestos in things like wall plaster and floor tile.  No amount of inhaled asbestos is safe, a known carcinogen.  How about nasty chemicals in the plastic containers your food is stored in?  Stuff dumped in the water, on the land, or pumped into the air by any nearby industries? 

You're free to deny that which can harm you, but the facts remain the facts.