Autism, pesticides and PR
At first glance, when an interest group publishes a report based on 158 scientific studies, there is something to celebrate. It is constantly regretted that science has a hard time making its way into public debates, so we are not going to sulk this pleasure, eh? But in this and other matters, the devil often hides in detail, and the David Suzuki Foundation’s report on the link between autism and pesticides is just another proof of that.
Thereport, published last week, is available here . It presents itself as a “review of the scientific literature” and explicitly points to pesticides as a major, if not the main, cause of the dramatic rise in autism diagnoses over the last 20 years – the number has been multiplied by almost 10 among Quebec students since 2001, according to a chart in the report.
The document had a nice echo, being taken by several media , unfortunately not always very critical – but sometimes yes , anyway. In fact, even Prime Minister François Legault was quoted as describing the phenomenon as “serious” and “disturbing” , that is to say. So it’s worth looking at this report more closely. Here’s what I remember, in bulk:
– Did you say “studies”? There are 158 references in the bibliography of the report, but not all of these “158 studies” are actual studies, and not all of them are all related to the alleged link between pesticides and autism. There are government reports, studies on lung inflammation by pollutants (ref 31), the effect of pollutants on mitochondria (part of cells that provides energy to the cell, ref 33). ), etc. There are also studies that look at the effect of pollution in general on autism, in which pesticides are described as just one environmental factor, and no more.
– Not all relevant. There are some studies in these references that really suggest a link between pesticides and autism. The David Suzuki Foundation has found quite a few, let’s say it. But even among them, there are some that are not as relevant as it seems. Some of them deal with DDT (and its derivative, DDE), an insecticide that was banned from use in Canada … in the 1970s. A few others look at the effects of another insecticide, chlorpyrifos, than the Canada is already preparing to ban most agricultural uses .
– Samsel and Seneff. As long as you’re in those studies: seriously, David Suzuki Foundation? Samsel and Seneff? Several “studies” of Anthony Samsel and Stephanie Seneff?!? They, who are really not experts in toxicology, the first was pro bono consultant in environment and the second, researcher in computer science? They have linked glyphosate (the world’s best-selling herbicide) to literally all modern diseases, from autism to obesity to cancer and what else? They, whose articles have been totally destroyed by just about all the real experts who have lost their time reading them? What are we playing at, exactly?
Listen, even close associates of Gilles-Eric Séralini have descended the “studies” of Samsel and Seneff in flames. For the record, Mr. Séralini is the lead author of the infamous 2012 study that claimed to “prove” that GMOs were carcinogenic, but whose methodological weaknesses were immense and whose results were then completely contradicted by other studies. better done. He has the reputation (well deserved) of being extremely and unnecessarily alarmist. Well, two of his collaborators concluded in 2017 that “the mechanisms and the wide range of medical conditions that Samsel and Seneff trace back to glyphosate in their commentaries are, at best, unsubstantiated theories, speculations, or simply incorrect”.
If even researchers with a reputation sulphurous strand as they distanced themselves, it says a lot about the value of these works. However, the David Suzuki Foundation’s report quotes several articles by Samsel and Seneff and devotes a few paragraphs to defending (following a dubious logic) their credibility. Pinch me, I must be having a nightmare.
– Dead angles. Beyond the not directly relevant references and dubious sources – I imagine that the Alternative Medicine Review (ref 132) looks not so bad when we quote Samsel and Seneff, joual-green I still do not come back of that – I repeat that there are some genuine studies done by serious researchers who suggest a possible link between autism and pesticides. It can not be said that the David Suzuki Foundation’s report is based solely on wind. But it can certainly be said that he has a blind spot : genetics.
The document passes very quickly (on page 4) on the genetic causes of autism, essentially to minimize its importance. However, many recent studies show that we are dealing with a very predominantly genetic phenomenon, but the not-so-well-named “literature review” of the David Suzuki Foundation says nothing about it. Not a word about the largest study ever undertaken on the issue , yet published this summer, which concluded that autism is “heritable” (read: genetics) at 80%. Not a word about it, published in 2017 , which places heritability at 83% and the environmental part at 17%. Not a word about this meta-analysiswho aggregated the data from twin studies on autism and quantified the proportion of genes between 64 and 91%. And many more.
But if the environment plays such a weak role, then the “hypothesis” advanced and presented as a virtual certainty by the David Suzuki Foundation does not absolutely hold the road: secondary factors can not explain (in any case, no more than very partially) that the number of cases has multiplied by 10. And it is even less plausible when, like the SDS, we focus only on a small part of these environmental factors (pesticides, but we suspect other environmental causes).
So we must logically look at the diagnoses (different criteria, better screening, awareness of medical and education, replacement of previous diagnoses by autism, etc.) to explain the rise in cases. But the “literature review” passes just as quickly on it as for genes, again here to minimize its importance. And she completely ignores studies like this one, for example , which found that a sizeable share of those diagnosed with “language development disorder” in the 1980s would most likely have been considered autistic if they were born 20 years later.
Note that all this is entirely consistent with the expert reactions when a study linking autism and pesticides comes out. Almost all of them argue that we are dealing first and foremost with a question of gene and diagnosis (see here , here and here ).
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There are not 56 possible conclusions to all this: the FDS left with a conclusion chosen in advance, which was consistent with its ideology and with the political and alarmist message it wanted to convey, so it was made a “literature review” tailored to your needs It was necessary to suggest as clearly as possible that pesticides are behind the rise in cases of autism, so exit the causes to some 80% genetic, exit diagnostics issues. And if it is necessary to scratch the backdrops into their most obscure roots to swell the “literature review” with irrelevant or spectacularly weak works, so be it , as they say.
In its defense, the document includes a section “Methodology” where it can be read that the review was made using only pesticide names as keywords. And where it is stated that “this review was not designed to be exhaustive”. In the words of her first author, Scientific Director of the SDS Louise Hénaut-Éthier, she explicitly mentioned in the Journal de Montréal that “I can not answer unequivocally:” pesticides cause autism “. Scientifically, I do not have the right “. She says that she and her report are only invoking the precautionary principle.
But frankly, it seems to me to be more convenient safe-conduct than serious nuance. After having spent 30 pages presenting a partial and distorting version of the scientific literature, it would be enough to bury a small sentence at the end of the document to get rid of it? After hammering the alarmist message “pesticides cause autism” in all available forums (and knowing full well that it would often be relayed as such in the media and on social networks), it would be enough to a small sentence to pretend we did not say what we just said?
In this respect, the conclusion of the document is quite telling (my underlining):
There is not much room for doubt in this paragraph. “Risk series”, “we must strongly restrict [pesticides]”, “risks and costs too high”, “we can not close our eyes”: if the shades had really imported in the eyes of the SDS, we would have found in its conclusion. They are not there. And it is not under the “precautionary principle”, which is not mentioned here, that the alarm is sounded here.
That, I believe, (re-re) demonstrates what kind of document we are dealing with here. This is not a review of scientific literature made for the purpose of understanding an issue. It’s a PR exercise. Nothing more.