Recently, Dr. Tracy Ann Becerra and colleagues from the Fielding School of Public Health at UCLA reported that air pollution is directly correlated with autism. That is, the more air pollution the more autism. A far as theories, the discussion in the paper showed the UCLA group did not think out of the box; all they could come up with was a discussion that pollutants in air are directly causing autism. If air pollution was causing the epidemic of autism, then that epidemic should have peaked in the 1950s, when air pollution in the USA was at its worst. Instead, it has yet to peak.
In the discussion of this paper, which included senior author Professor Beate Ritz who is vice-chair of the Public Health department at UCLA, the authors made no mention of how air pollution blocks UVB radiation and thus lowers vitamin D levels, a fact shown by a French paper published just a few months earlier. In the defense of the UCLA group, the delay in the review process for their paper may not have allowed for it. The French group found surface air pollution was strongly associated with lower vitamin D levels in newborn infants.
Baïz N, Dargent-Molina P, Wark JD, Souberbielle JC, Slama R, Annesi-Maesano I; the EDEN Mother-Child Cohort Study Group. Gestational Exposure to Urban Air Pollution Related to a Decrease in Cord Blood Vitamin D Levels. J Clin Endocrinol Metab. 2012 Nov;97(11):4087-4095
I blogged on the French paper when it came out online in September.
In fact, in my original paper on autism, I pointed out that studies associating air pollution with autism are perfectly consistent with the vitamin D theory of autism.
We have a more detailed description of the vitamin D autism connection here:
The best explanation of air pollution’s effects on the incidence of autism must be parsimonious, that is, take in all the other facts known about autism and explain them all simply. As Kurt Vonnegut once said,
“I am fond of Occam’s razor, or the law of parsimony, which suggests that the simplest explanation of a phenomenon is usually the most trustworthy.”