How much of weed can you smoke before it kills you?

Excerpt from WebMD:

"The risks of smoking marijuana go up with heavy use. Although the link has never been proven, many experts believe heavy pot smokers are at increased risk for lung cancer.

Heavy marijuana use lowers men's testosterone levels and sperm count and quality. Pot could decrease libido and fertility in some heavy-smoking men.

Contrary to what many pot smokers may tell you, marijuana is addictive, at least psychologically. Even among occasional users, one in 12 can feel withdrawal symptoms if they can't get high when they want to. Among heavy pot smokers, the rates of dependence are higher."