chernobyl 4000 - 1000000
http://www.utne.com/Wild-Green/Chernobyl-Death-Toll-4000-or-1-Million-7272.aspx

Nicotine - Around 5.4 million deaths a year
http://www.inforesearchlab.com/smokingdeaths.chtml
http://emedicine.medscape.com/article/287555-overview
http://library.thinkquest.org/3230/facts.htm
The Center for Disease Control and Prevention reports that : cigarette smoke is responsible for more deaths each year than ones caused by AIDS, alcohol, car accidents, cocaine, crack, heroin, fires, homicide, and suicide combined. 


Traffic (Spain)
2004 -> 1.2 Million + 50 Million injuried
http://en.wikipedia.org/wiki/Traffic_collision


Bhopal (India, 1984) -> 16000