SR LAB TECH WAS IN QUALITY CONTROL LAB PERFORMING TESTS. HE PICKED UP 5 GAL CARBOY OF COTRIC ACID FROM THE FLOOR, CARRIED IT ACROSS THE ROOM, AND ATTEMPTED TO PLACE IT ON A HEAD HIGH SHELF AS HE STEPPED UP ONTO A STEP STOOL. AS HE RAISED THE CONTAINER, HE FELT PAIN IN HIS LEFT LOWER BACK. HE CONTINUED TO WORK, BUT THE PAIN WORSENED OVER THE NEXT SEVERAL DAYS UNTIL ON 4/12 WAS UNABL