Urban legend. Smoking marijuana sprayed with paraquat has no ill effects. The myth was propagated by anti-drug activists to deter the smoking of pot in general.
Gullible Moron: Oh shit, I hope I don't have the paraquat lung from this shwagg
Enlightened Skeptic: Don't worry, that's just a myth constructed by the fascists and religious fundamentalists who want to legislate morality.
Lung disease caused by the contact herbicide paraquat which selectively accumulates in the lungs and is highly toxic. Once X-rays show changes from paraquat are evident in the lungs, death is virtually certain.
Paraquat lung emerged as a health concern in the 1970s, when the US government sprayed paraquat aerially over some illegal marijuana fields in Mexico. Some of the sprayed plants were harvasted prematurely before they died, causing paraquat lung in purchasers who smoked it.
Oh shit, i hope i dont have the paraquat lung from this shwagg, wait, i never smoke shwagg....