There they go again: a group of academics long-devoted to finding pesticide toxicity by any means necessary has accomplished their goal! What goal, you ask? They have attained a vast amount of media attention (sure, mostly in the enviro-blogosphere, but many mainstream folks have swallowed this whole as well, thanks to the PR folks at UC-Davis and that font of anti-chemical nonsense, Environmental Health Perspectives).
This poor excuse for a scientific study lacks only a few of the sine qua nons required for even an association linkage. No actual measurements of pesticide exposure were conducted, given that the data was collected retrospectively: there could have been no actual measurement of pesticide exposure and there was none. The attempted estimation of such exposures were made by determining the addresses of the study subjects at the time of their pregnancy and in the few weeks beforehand, and tabulating their distances from large-scale pesticide applications. The research group then attempted to discern which among several pesticides and pesticide-classes were predominantly used and compared those approximates to the distances away by the women. Almost 1,000 women were initially entered into the study, 486 autism-spectrum disorder (ASD) infants were studied and compared with 316 infants with normal development (an attempt to include developmentally disabled infants was abandoned due to an inadequate sample size).
From a statistical point of view, the best data points were cherry-picked, with variable trimesters of most adverse effects presumed for various chemical inputs, without any rhyme or reason as to why or how one class allegedly affected infants due to 2nd -trimester exposures as compared to others being affected by other chemicals in the 3rd trimester, with similarly scattered distance-effect relationships: clearly the authors selected what they felt were the most impactful associations based on their own retrospective, results-in-mind analysis. This is how data-dredging is carried out, and is successfully foisted on the unsophisticated journalists as if it meant something. Aside from garnering the required publicity, that is: for the authors, for UC-Davis, for the journal, for the reporter and his/her media outlet, and (most disturbingly) for the anti-chemical enviro-lobby.
ACSH s Dr. Gil Ross had this comment: While the authors puerile agreements that this is just an exploratory study and it s just one small piece of the autism puzzle were dutifully noted, their comments in other sites revealed their true perspectives: the lead author, Dr. Janie Shelton, had this to say to the SFGate blog: This study validates the results of earlier research [by her and her group!] that has reported [similar] associations ¦ , while the group s leader, Dr. Irva Hertz-Picciotto, added (to the UC-Davis press release): If it were my family, I wouldn t want to live close to where heavy pesticides are being applied. (Bolded and italics are the editors').
From Ross again: By all means, Dr. Hertz-Picciotto, don t live within 5 miles of any ag-chemical if you choose not to although that will be difficult I d say in central California, the nation s breadbasket. But this study should not be the basis of any such advice to the public! I d also like to note that she the leader of this group has been a member of the science advisory board of the anti-chemical, anti-vaccine group Autism Speaks, and other devoted anti-pesticide NGOs, a fact nowhere disclosed in this article. Just another brick in the wall of propaganda and chemophobia behind this thoroughly junk study. While a snake is a snake it doesn t hide, you know its dangers up front so the crusade of these folks should be well known and no longer surprising, yet it s disappointing that the gullibility of the media allow this claptrap to be reported as though it were solid science, when the opposite is the case.
For the real science behind pesticides, see ACSH s publications.