The biggest hazard of ecstacy is that it shuts down the body's cooling process so there is high risk of hyperthermia, which in Toronto was the cause of most ecstacy-related deaths during a wave of such incidents a few years back. Non-stop dancing, poor ventillation and lack of available water were all cited when those deaths were investigated (most raves here were underground, often held in unsuitable facilities). The deaths stopped when the city made it easier to operate all-ages rave parties legally and the police were ordered to crack down on the raves being held in unsafe venues.