
New insights on pesticide exposure and autism - mhkool
https://factor.niehs.nih.gov/2018/9/papers/autism/index.htm
======
nerdponx
_METHOD: The investigation was derived from the Finnish Prenatal Study of
Autism, a national birth cohort study based on a nested case-control design.
Cases of autism among children born between 1987 and 2005 were ascertained by
national registry linkages. In cases of childhood autism and matched control
subjects (778 matched case-control pairs), maternal serum specimens from early
pregnancy were assayed for levels of p,p '-DDE and total levels of PCBs.

RESULTS: The odds of autism among offspring were significantly increased with
maternal p,p'-DDE levels that were in the highest 75th percentile, with
adjustment for maternal age, parity, and history of psychiatric disorders
(odds ratio=1.32, 95% CI=1.02, 1.71). The odds of autism with intellectual
disability were increased by greater than twofold with maternal p,p'-DDE
levels above this threshold (odds ratio=2.21, 95% CI=1.32, 3.69). There was no
association between total levels of maternal PCBs and autism.

CONCLUSIONS: These findings provide the first biomarker-based evidence that
maternal exposure to insecticides is associated with autism among offspring.
Although further research is necessary to replicate this finding, this study
has implications for the prevention of autism and may provide a better
understanding of its pathogenesis._

This would be more convincing if someone went and correlated DDT contamination
levels in a region with autism levels in the same region.

~~~
Bjartr
Why is that more convincing? Since people can move around, and your exposure
levels during pregnancy won't necessarily line up with the environment the
child lives in (and thus informs the rate of autism statistic), I would expect
this serum assay to be a more convincing measure. Am I missing something?

~~~
alexandercrohde
What you're missing is that most chemical damage to infants is done in-utero,
at their most vulnerable time (why you don't drink when pregnant).

~~~
Bjartr
No, I explicitly accounted for that, which is why I mentioned that measuring
the rate of autism (which is measured as the number of people diagnosed with
autism in a region) might not line up with exposure during pregnancy (which
could have occurred in a different region entirely, especially if the autism
diagnosis lags behind the birth)

~~~
alexandercrohde
What are you talking about? Region and location has nothing to do with this
study.

They took the serum of the pregnant mother, measured that for the pesticide,
and found it was a statistically significant predictor of autism.

~~~
nerdponx
The whole thread is responding to my suggestion that you ought to also find a
geographical relationship between DDT application and autism.

~~~
alexandercrohde
Oh, shit, you're right. I didn't read your part not-in-italics.

Well, I suck. I was rude and incorrect. Thank you for taking the time to keep
me humble.

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madrox
FWIW, this is a case-control study, which has huge limitations in
generalizability of conclusions. You probably learned about them in your intro
to statistics course. Take this with a grain of salt.

Case control studies in themselves can't prove causation. It can, however,
make shadowy insinuations that are definitely worth following up on in a more
rigorous way. The first indications smoking caused lung cancer came from a
case control study.

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scott_s
I would like to see the same investigation in a different population. The
difficulty is that we don't know how many different kinds of associations they
looked for in this population - they mention no link between PCBs, but that
doesn't necessarily mean they _only_ looked for an association between DDE and
PCB. If, for example, they looked for an association between 100 compounds,
the chances are pretty good that there would be some positive correlation from
at least one of them.

Doing the study in a different population, where you're only looking for this
one particular association increases the likelihood it's not just chance.

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nigelcleland
If you haven't read it pick up a copy of _Silent Spring_ by Rachel Carson
which covered the indiscriminate use of pesticides and the effect on the wider
ecosystem.

The awareness she helped raise contributed to the founding of the EPA and the
banning of DDT.

~~~
gadders
>>The awareness she helped raise contributed to the founding of the EPA and
the banning of DDT.

..and caused the deaths of millions of people to malaria [1]

[1] [https://www.thedailybeast.com/how-rachel-carson-cost-
million...](https://www.thedailybeast.com/how-rachel-carson-cost-millions-of-
people-their-lives)

~~~
gowld
That's a controversial claim.

[https://en.wikipedia.org/wiki/DDT#Criticism_of_restrictions_...](https://en.wikipedia.org/wiki/DDT#Criticism_of_restrictions_on_DDT_use)

and you have to balance the effects of reduced DDT use (even if that did cause
malaria resurgence) against the overall effects of getting public interest
into the consequences of newly invented chemicals, and creating the EPA and
general oversight of pesticides.

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eiieirurjdndjd
If they had studied number of mosquito bites received and the probability of
autism, would they have gotten the same result? Or if they studied outdoor air
temperature during pregnancy and autism, would they have seen a link? Probably
... so be careful about assuming causality here.

~~~
dmm
Autism has also been linked to maternal age. Maybe older women just happen to
also have more DDT because they had more time to accumulate it or they were
alive longer for when DDT was widely used.

~~~
Rovanion
The study controlled for that:

> The odds of autism among offspring were significantly increased with
> maternal p,p'-DDE levels that were in the highest 75th percentile, with
> adjustment for maternal age, parity, and history of psychiatric disorders...

~~~
kaitai
They also could/should have adjusted for paternal age, which may be a
significant factor (see [1] for lots of links). (There is some interesting
statistical stuff going on with paternal age -- some researchers claim if you
bin by birth year some of the paternal effect disappears, which is odd!
However, the article under discussion considers only children born between
1987 and 2005, so it's not a huge range of birth years...) They do have data
on paternal age, but they don't include it in Table 1. Odd.

[1] [https://www.spectrumnews.org/news/link-parental-age-
autism-e...](https://www.spectrumnews.org/news/link-parental-age-autism-
explained/)

------
dvfjsdhgfv
> Although banned for more than 30 years in many countries due to suspected
> health effects, chemicals such as DDT and PCBs still exist in the
> environment due to their slow breakdown and the way they accumulate in
> plants and animals in the food chain. According to the CDC, most of the U.S.
> population has detectable levels of DDE

These sentences are crying out loud to all of us, especially all of us that
are pushing products meant to be eaten, applied on skin, sprayed in the air,
sprayed on plants we eat, without adequate and long-term testing, focusing
only on perceived short-term advantages (Was DDT efficient? Damn it was!)

~~~
bluGill
How do you do a long term study on anything though? genetic mutations are
fairly common. Take any large sample of anything living and there will be
genetic differences. Even a field of roundup-resistance GMO corn after sprayed
with roundup will not all have the same DNA, and I just gave the best odds of
killing anything not the same DNA. You cannot know for sure that one of those
random mutations isn't very harmful, and there is no way to know which of the
thousands of plants actually has the mutations that need to be tested - nor do
you even know which mutations will survive more generations (because they are
from a grandparent seed plant)

~~~
dvfjsdhgfv
It was very difficult back then, it's even more difficult now. Think about 5G:
we know already that it's a huge safety hazard[0]. But we'll use it when it's
out anyway. Why? Because of short-term benefits. Because the negative effects
cannot be measured immediately. Because the tech industry is extremely
powerful and there is no way we can avoid 5G, it's simply too late.

[0] [https://www.thenation.com/article/how-big-wireless-made-
us-t...](https://www.thenation.com/article/how-big-wireless-made-us-think-
that-cell-phones-are-safe-a-special-investigation/)

~~~
bluGill
The article you linked can be summed up in this line in the middle: "The
absence of absolute proof does not mean the absence of risk". In short this is
a religion: you cannot prove me wrong therefore I'm right.

~~~
gowld
Scientific research can be used to answer questions. We don't need to rely on
faith one way or the other. That's why these scientists are calling for a
moratorium and safety research.

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fallingfrog
This might be a true association but still not explain most of the cases of
autism in kids being born today- DDT has been illegal in most countries for 30
years. There must be something else accounting for the more recent cases-
perhaps another chemical having a similar effect.

~~~
alexandercrohde
Yeah. Seeing how long it has taken us to find this DDT-Autism link it makes me
wonder how many other pesticides since have an uncaught link.

~~~
gowld
This isn't a DDT-Autism link, it's a preliminery curiosity in the data that is
motivating further research.

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mrfusion
Are bug sprays safe? Is deet different from ddt or are they similar molecules?

~~~
colanderman
DEET (a repellent) is not DDT (a poison). Use Icaridin/Picaridin or Oil of
Lemon Eucalyptus (not Lemon Eucalyptus Oil) if you don't want to use DEET. All
three are commonly available in the US, demonstrated to be highly effective,
and recommended by the CDC: [https://www.cdc.gov/zika/prevention/prevent-
mosquito-bites.h...](https://www.cdc.gov/zika/prevention/prevent-mosquito-
bites.html)

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kosma
Could some research-savvy person check the paper to see if there's any
causality proven, or just correlation?

~~~
tboyd47
Longitudinal studies are typically observation only, so even the stronger ones
won't establish causality. But that doesn't mean the conclusions aren't
valuable.

For example, if we know that DDT exposure in particular increases the risk of
autism, then we can start looking at how those chemicals interact with cells,
and find out more about autism at the biochemical / cellular level and even
create a drug that counteracts those processes. Then we get into experimental
trials which do establish causality.

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throwawayperson
Modern psychology seems more and more plausible

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dreamcompiler
Yay for real science! I hope this means we can go back to being a measles-free
society again.

