A Grandfather Clause in a Regulation Typically Exempts Existing Facilities

Essay

A grandfather clause in a regulation typically exempts existing facilities or operations from the new regulation.For example,the Clean Air Act of 1970 exempted existing plants from the regulation,affecting only new plants.What was the rationale for including a grandfather clause in something like the Clean Air Act of 1970? Describe a negative result of the grandfather clause used in the 1970 act?