How dangerous is an industrial scale styrene spill? A few years ago a cisterna truck full of styrene crushed on the road near a small town nearby, spilling 4 tons of the chemical. It apparently has caused a small ecological catastrophe killing fish in the local river with concentrations of 3.7 ml/l in the water, and half of the population - some 2000 people were evacuated in the next 2 days, but it was not mandatory, and what seems more strange to me, I've seen all the firefighters not wearing any gas masks while pouring some white foam on the truck. Also, no one mentioned that styrene is a cancerogen.

Initially, there was no info on the chemical spilled, and I didn't know or care much then, but today I incidentally found out it was styrene, and I got curious. So, were those measures somehow inadequate, or on the contrary - far-fetched, and just how bad this is?
According to this safety data sheet (SDS), styrene monomer has a Category 3 respiratory classification, where 1 would be most serious. Category 3 is defined "substances produce transient (short duration or temporary) target organ effects." 

Add to that these hazard, precautions and carcinogenicity statements: 


H335: May cause respiratory irritation.
H372: Causes damage to organs through prolonged or repeated exposure if inhaled.
P260 Do not breathe dust/fume/gas/mist/vapor/spray.
NTP Reasonably anticipated to be a human carcinogen


Read the cited SDS or others for statement on environmental precautions and cleanup. Frankly, they're a bit vague to me, "If the product contaminates rivers and lakes or drains inform respective authorities."