The sum of the concentration levels of lead, cadmium, mercury, and hexavalent chromium present in any package or packaging component shall not exceed the following:

(1) Six hundred parts per million by weight effective July 1, 1993;

(2) Two hundred fifty parts per million by weight effective July 1, 1994; and

(3) One hundred parts per million by weight effective July 1, 1995.

This section shall apply only to lead, cadmium, mercury, and hexavalent chromium that has been intentionally introduced as an element during manufacturing or distribution.