An upstate New York librarian claims that her MCS (Multiple Chemical Sensitivity) was caused by exposure to mold at the library where she worked. She's now so ill she can barely leave her house. Today industrial hygienist Monona Rossol and Dr. David C. Straus explain why some mold can be so toxic, and whether you should be concerned about your workplace. Ms. Rossol is also founder and president of Arts, Crafts & Theater Safety, Inc., and Dr. Straus is Professor of Microbiology and Immunology at Texas Tech University.