On May 25, 2004, at approximately 1 p.m., a passenger walked to the front of public TransLink bus #98 in downtown Vancouver, BC, as the bus stopped at an intersection. As one bus passenger recalled, the disembarking passenger asked the bus driver how his day was going. After the bus driver said, "good," the man responded, "It won't be for long." As the driver continued his route, he began to feel nauseated and later vomited after traveling 10 kilometers from where the man left the bus. The bus driver then asked if any passengers felt ill. When one passenger said, "yes," the driver, fearing a chemical attack, parked the bus and radioed for paramedics. As the two responding paramedics began to treat the driver and hear his version of events, they too fell ill. Others arriving on the scene also felt sick. The controversial investigation failed to produce any objective evidence of a toxic cause of the illnesses, although a private firm hired by the police identified methyl chloride as the chemical that produced the illnesses. This conclusion, however, did not fit the facts of the case and was rejected by Vancouver's Chief Medical Health Officer, who maintained that the cause was "mass anxiety" or MPI, which stems from a psychosomatic experience whereby powerful anxiety causes adverse physical consequences. Since 9/11, rumors of chemical and/or biological terrorism are particularly potent triggers of public anxiety. 41 references