Workers at University of Texas System campuses in Houston and San Antonio were potentially exposed to biological weapons agents during laboratory mishaps in the spring, according to records obtained by a watchdog group. Four workers at the UT Health Science Center at Houston might have been exposed to the bacteria that cause anthrax as a result of a leak from faulty tubes with screw caps that did not seal properly, campus records show. Three workers at UT-San Antonio entered a tularemia lab without donning the required respiratory protection. That lab is working to develop a vaccine for the disease, also known as rabbit fever.