On 5th July 2013, a train left Montreal travelling East to St John, New Brunswick carrying over 7000 tons of crude oil for processing at an oil refinery. The oil originated in the Bakken Formation in North Dakota and had probably been fracked out of its bedrock. The previous year, rail company had convinced the rail regulator that it was okay to put such trains - 1.4 km long (!) consisting of five engines, 72 brim-full oil-tankers and a caboose - in the sole charge of a single engineer (SPTO - single person train operation). At around midnight, at the end of a long day's work, this engineer stopped his train, leaving one diesel engine running to maintain pressure in the air brakes, called a taxi and went off to a hotel for the night. Shortly afterwards a passer-by noticed that the running engine was on fire, and called the fire-brigade. They arrived, switched off the engine (following their standard operating procedure), extinguished the fire and went back to base. As soon as nobody was watching the train started to move s l o w l y forward under the gravitational force of a 1% slope. Twenty minutes later it had gone 11km and arrived in the middle of downtown Lac-Mégantic travelling at 100km/h without lights and left the rails on the first significant curve in the track. 60 of the tanker-cars trundled into the streets and started spilling their loads which didn't take long to ignite; the fire ruptured more tankers in a chain-reaction that wasn't brought under some sort of control until tea-time 16 hours later. The oil spilled into the sewerage system and caused a succession of explosive eruptions blowing manhole covers into the air. Very few people were injured compared to the 40-50 people dead: a wall of burning oil is not a half-measure thing, and about as hard to out-run in bare feet as a tsunami.
I can now add another substance to the table of relative amounts it takes to kill one person