I mean are we talking something like chlorine, or hydrocarbons or something more specifically nasty like dioxins or Mercury?
"According to a news release, the leak happened at Freedom Industries in Charleston. The leaked product is 4-Methylcyclohexane Methanol, which is used in the froth flotation process of coal washing and preparation."
The percentile table is:
0-9% - Immediate radiation sickness dealing additional 15HP of damage, and a lifetime of random, scattered benign tumors & cysts
10-49% - Coin flip for damaged infertile gonads or ruined thyroid, damaged thyroid inflicts 5HP per day
50-59% - Blindness
60-69% - Leukemia, with a coin flip for six month or decade-long survivability
70-79% - Other chronic malignant cancers with three year suvivability
80-89% - Other acute malignant cancers with six month survivability
90-99% - Instant death