I have included a link to a very interesting article.
It includes the reference of being OK with a certain amount of lead paint in our children's cribs.
I have said many times that we need to check our thinking "Is what you are thinking true?"
Marijuana (more explicitly THC) is a drug, plain and simple, not a "soft drug" it does exactly the same thing in the brain as any other drug including alcohol, it changes how we feel.
That is dangerous ground for a teen.
Please give this a read. http://www.weeklystandard.com/blogs/colorado-kicks-57-million-campaign-encourage-safe-pot-use_823332.html