In October 1979, a technician in the electron microscopy laboratory of one of the teaching hospitals in Toronto spilled a bottle containing approximately 500 ml of 2% osmium tetroxide. He asked for help, and four other technicians were involved in the cleanup. They all were exposed to osmium tetroxide vapours for long enough to show signs of acute intoxication. They developed redness and swelling of the conjunctiva, impaired vision, chest pains, breathing difficulties and skin irritation and were taken into Emergency Care at the hospital. The occular symptoms disappeared after two days, but the chest pains and breathing difficulty persisted for approximately one week.

This accident could have had more serious consequences. It has been reported that exposure to osrruum vapour could lead to blindness and serious respiratory trouble. At McMaster University Medical Centre, the safety committee gives precise procedures to be followed in case of accidents with dangerous chemicals. All the occupants of the laboratory have to leave immediately and phone the safety and security team.