Could be, but I think he was probably just exposed to some second-hand smoke, and the traces of THC found in his system had nothing to do with his ill-health. On the other hand, if his folks did indeed feed him ganja brownies (or cookies) or intentionally blow high-grade smoke in the kid's face, then his condition probably was a result of the THC consumption, and his parents should be held liable.
Of course that was referring to people taking drug tests who might have been exposed to secondhand smoke at parties. I imagine if you were a toddler living with a bunch of chronic potheads things might be different.