Section 235. Exemptions

Any  employee who is receiving or is entitled to
  receive old-age  insurance  benefits  under  title  two  of  the  social
  security  act,  shall  be  exempt from this article upon filing with the
  chairman and his employer a statement, in  such  form  as  the  chairman
  shall  prescribe,  waiving  any  and  all  benefits  under this article.
  Thereafter  such  employee  shall  be  exempt  from  any  liability   to
  contribute  toward  the cost of such benefits, and his employer shall be
  relieved of responsibility to provide for the payment of any benefits to
  such employee under this article.