Pesticides Now, Autism Later?

A lot has been proposed about “this causes autism, that causes autism”.

Perhaps the most famous one is “vaccines cause autism”, in which case: Debunking the myth that vaccines cause autism

That said, there is one way that being unvaccinated can reduce the risk of being diagnosed with autism, that is if you (or the child in question, as it’s often about a child) die due to being unvaccinated, because in order to get an autism diagnosis, you have to be alive.

However, dying to avoid an autism diagnosis is not a sensible strategy, for obvious reasons.

What, then, of Tylenol*, which got a lot of media attention in recent history? It’s OK to use paracetamol in pregnancy. Here’s what the science says about the link with autism

^{*of which the actual drug name is acetaminophen in the US, and paracetamol in most of the rest of the world.}

Not that Tylenol is exactly in the clear when it comes to real health risks, though: Before You Reach For That Tylenol…

As for the latest contender, let’s get into it:

The pesticides that attack the nervous system

This time, there is at least a plausible hypothetical mechanism of action: the pesticide in question works by interfering with the nervous system.

Or rather, the class of pesticides, since this is about organophosphate pesticides specifically.

Researchers (Dr. Heather Volk et al.) investigated whether prenatal exposure to organophosphate pesticides is associated with autism-related traits in childhood, including whether associations differ by the child’s sex or the mother’s diet.

In terms of scope, the analysis included 3,339 mother-child pairs from 20 US medical centers participating in the NIH Environmental Influences on Child Health Outcomes (ECHO) cohort. The children were then assessed for autism-related traits at an average age of 6.4 years.

Here’s how they checked both things:

• Pesticide exposure: researchers measured urinary biomarkers of organophosphate exposure, including TCPy and the combined DAP (also written as “ΣDAP”, meaning “the sum of the DAP”) metabolites. Organophosphate pesticide exposure was widespread, with 99% of mothers having detectable levels during pregnancy (though those levels varied widely, so the data was indeed useful).
• Autism-related traits: parents completed the Social Responsiveness Scale, which measures characteristics such as difficulties with social communication, eye contact, understanding emotions, and repetitive or rigid behaviors, including in children without a formal autism diagnosis.

In few words: after adjusting for maternal sociodemographic factors, prenatal organophosphate exposure was not significantly* associated with autism-related traits in childhood.

^{*Quick reminder that when scientists say “significantly”, this isn’t about extent, it’s about statistical significance, so what they’re saying here is not “it was associated just a little a bit”, they’re saying “we could not honestly establish an association”}

Looking at the numbers in this case:

❝Crude or minimally adjusted models suggested inverse associations between prenatal TCPy or ΣDAP levels and SRS scores, but these associations attenuated and lost statistical significance after full adjustment (β per doubling of TCPy concentration [ng/mL] = −0.13; 95% CI, −0.57 to 0.31; β per doubling of ΣDAP [nmol/L] = −0.42; 95% CI, −1.03 to 0.19). Results were consistent across sex-stratified models, secondary analyses using quantile and logistic regressions, various sensitivity analyses, and after adjustments for dietary confounders. There was no evidence of effect modification by diet quality.❞

Translating from sciencese: the results showed both increasing and decreasing tiny association on both sides for both tests, in other words, the pointer is wobbling around zero and we’d have to rely on p-hacking or similar to pretend this tells us it has an effect on risk.

You can find the paper itself, here: Prenatal Organophosphate Exposure and Autism-Related Traits in Children

Caveat: this does not mean the pesticides are safe. They are not. The chemicals involved are literally designed to be neurotoxic (just like The Common Pesticide That Causes Brain Damage).

Nor are pesticides great in other ways, for example: How Much Do Pesticides Increase Cancer Risk?

All this study says is “no, this almost certainly has no bearing on autism”.

Want to learn more?

And for a much deeper dive into the broader topic of avoiding the toxins the industrial world is keen to throw our way, you might like this book that we reviewed a little while back:

Healthy Living in a Contaminated World – by Dr. Donald Hoernschemeyer

Take care!