Like for example: Radium (used in all manner of products meant for human consumption), Thalidomide and asbsestos (used everywhere in building materials).

Or BSE (mad-cow disease; at the time, the UK minister of agriculture, John Gummer, publicly fed his daughter a beef burger to show there was no danger from consumption of Brittish beef) though that one is not a technological solution, as such; but it's a well-known case were risk was underestimated.