I would suggest that 11 hours playing any game intensively would induce some sort of adverse reaction.
Or perhaps it is the mah jong tiles themselves. It seems everyday we hear some story of a Chinese-made good sold here in the States with a horribly toxic ingrediant(pet food, toothpaste, children's toys, etc.). Maybe the makers of mah jong equipment have used some seizure-inducing chemical in the manufacturing process. That could explain it.
Perhaps some American company could export to China gloves which could help mah jong players avoid contact with the tiles while playing. Hey! That's My Economic Opportunity!
Oh, wait. We closed all our manufacturing plants. Never mind.