Most people's understanding of basic math, and ability to precisely follow directions, is terrible. What's to prevent you from ending up with a concentration that's 10x or 100x what you intended?
I heard a story once about a research chemist who decided to synthesise LSD for his own use, miscalculated and gave himself a massive overdose-it didn’t kill him, but it rendered him non compos mentis for an extended period. Even domain experts can make dumb mistakes, especially when you separate them from formalised quality control systems aimed at catching those mistakes before anyone is harmed.
Risks, there are risks everywhere. Late Philosopher of Science, Larry Laudan wrote a little book--The Book of Risks: Fascinating Facts About the Chances We Take Every Day
