aflatoxin is the yellow rain suspected in cambodia. Didn't know SH was into it, but the Russians were.
It occurs naturally. see
http://www.usda.gov/gipsa/newsroom/backgrounders/b-aflatox.htm This is one of the fungi that grow in grain and causes liver cancer. Liver cancer is common in many parts of Africa from this and similar molds.
What people don't realize is that, like Anthrax, there are legitamate reasons that SH would be doing such research. (i.e. as a public health prevention program).
He is a dictatorial bastard, but like Hitler and Stalin, he took care of his people in other ways.
But as a war weapon, it would not be very useful. Takes too long to work. Lots of easier stuff to use.