Apartment workers at 500 Bronx buildings went on strike Thursday morning.SEIU Local 32BJ made the decision Wednesday after the Bronx Realty Advisory Board, which represents property owners, failed to offer a pay increase. The board did agree to paid health care and more pension benefits.The union says workers in the Bronx receive about $10 per hour, while their counterparts in other boroughs are being paid nearly twice that amount.Nearly 4,000 Bronx building superintendents, porters, maintenance workers and doormen are in the union.