But the US violates the UN Declaration of the RIghts of a Child
  by exposing people under 18 years old to conditions with hot oil
  and very dangerous working conditions.

  There are other aspects of what is considered acceptable in the
  USA for people under the age of 18 to do that might be
  unacceptable in other countries. I believe some of our rules
  involving family businesses violate it as well.

  For example, children can work at a restaurant their parents
  own.

  They can also do heavy farm work at a profit making farm.

  I don't remember them all, but as far as I know, the issues
  pointed out by the United Nations back in 1990, are still true
  in 2015.

  We consider such things normal here in the USA.