I have not voted on it, but if I were downvoting, my reasoning would run that this is a single link which many of us heard about at the time, and Gerard is not providing any context, real commentary, or comprehensiveness, and to some extent, he's focusing on uninteresting things: iodine is way cheaper than parasite prevention, as effective, and comes with nifty bonuses like 'increases the IQ of females more than males'. As well, the appeal to sanity waterline is a little misplaced without any reference to any of the papers I've been collating in http://lesswrong.com/lw/7e1/rationality_quotes_september_2011/4r01
Discussion has low standards, of course, but 1 link and 3 sentences is a bit low.
comes with nifty bonuses like 'increases the IQ of females more than males'.
Why is that a bonus?
This is interesting, I wonder if there's anything to it: International variation in IQ – the role of parasites (paper) by Christopher Hassall of U. Carleton.
It strikes me as the sort of thing that could be as big an issue as lead in the environment. Raise the sanity waterline: improve health!