6 ms·

New insights on pesticide exposure and autism

68 points by mhkool 8y ago

throwawayperson 8y ago
Modern psychology seems more and more plausible
eiieirurjdndjd 8y ago
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 8y ago
  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.
  - eiieirurjdndjd 8y ago
    Presumably they at least controlled for age race and socioeconomic level. If they didn’t then the results are very suspicious.
    - skosuri 8y ago
      "Adjusted for maternal age, parity, and maternal history of psychiatric disorders"
  - Rovanion 8y ago
    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 8y ago
      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-explained/ https://www.spectrumnews.org/news/link-parental-age-autism-e...
- dsfyu404ed 8y ago
  I can already see the click-bait headlines: "mosquito bites linked to autism" "outdoor recreation during pregnancy may cause autism" "are children conceived on camping trips more likely to be autistic?
- ams6110 8y ago
  Mentioning mosquitos, we need to keep in mind that (if the conclusion of the study is true) we traded a small--and at the time not understood--increase in autism for a huge decrease in mosquito-related disease. Millions of people who would have died in childhood are alive thanks to DDT and other insecticides.
  - gascan 8y ago
    Yes, and at the time it might have been a good tradeoff- but today we can do better, at least outside the malaria belt.
nigelcleland 8y ago
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.
- grecy 8y ago
  I'm re-reading it now. If you loved it, checkout Ishmeal by Daniel Quinn[1]. It's a fascinating way to further understand what we're doing to the planet and why we are able to so easily justify it. [1] https://amzn.to/2MOZciN https://amzn.to/2MOZciN
- gadders 8y ago
  >>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-millions-of-people-their-lives https://www.thedailybeast.com/how-rachel-carson-cost-million...
  - gowld 8y ago
    That's a controversial claim. https://en.wikipedia.org/wiki/DDT#Criticism_of_restrictions_on_DDT_use https://en.wikipedia.org/wiki/DDT#Criticism_of_restrictions_... 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.
nerdponx 8y ago
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.
- superpie 8y ago
  Has anyone found the full text of this tax funded study published anywhere that's not charging $35 to read it?
  - nerdponx 8y ago
    I have the same complaint. If you aren't affiliated with university library, or for some reason you aren't willing to use Sci-Hub, then probably not.
    - bjourne 8y ago
      Why would you not be willing to use scihub? http://sci-hub.tw/10.1176/appi.ajp.2018.17101129 http://sci-hub.tw/10.1176/appi.ajp.2018.17101129
dvfjsdhgfv 8y ago
> 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 8y ago
  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 8y ago
    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-think-that-cell-phones-are-safe-a-special-investigation/ https://www.thenation.com/article/how-big-wireless-made-us-t...
    - bluGill 8y ago
      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.
dreamcompiler 8y ago
Yay for real science! I hope this means we can go back to being a measles-free society again.
fallingfrog 8y ago
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 8y ago
  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 8y ago
    This isn't a DDT-Autism link, it's a preliminery curiosity in the data that is motivating further research.
- hyperpape 8y ago
  DDT is very stable and bioaccumulates. I don't know how much exposure a woman giving birth in the 2000s would have relative to earlier years, but I don't think you can assume it's that low. My instinct is that based on the study's moderate effect size and the lack of strong birth order effects or links to breastfeeding in autism, this effect can't explain the dramatic rise in autism diagnoses in the past several decades. I'm not a scientist, so take this with a grain of salt.
- chimeracoder 8y ago
  > 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. Not necessarily. The effects could be transgenerational (there's already precedent for that with other substances and executive function disorders, of which ASD is one[0]). Even the rise in autism cases isn't necessarily evidence against this link, because the ability to diagnose people 30+ years ago was dramatically different from our ability to properly diagnose people today. [0] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3931498/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3931498/
scott_s 8y ago
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.
kosma 8y ago
Could some research-savvy person check the paper to see if there's any causality proven, or just correlation?
- tboyd47 8y ago
  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.
mrfusion 8y ago
Are bug sprays safe? Is deet different from ddt or are they similar molecules?
- colanderman 8y ago
  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.html https://www.cdc.gov/zika/prevention/prevent-mosquito-bites.h...
madrox 8y ago
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.

68 points by mhkool 8y ago

Modern psychology seems more and more plausible

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 8y ago
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.
- eiieirurjdndjd 8y ago
  Presumably they at least controlled for age race and socioeconomic level. If they didn’t then the results are very suspicious.
  - skosuri 8y ago
    "Adjusted for maternal age, parity, and maternal history of psychiatric disorders"
- Rovanion 8y ago
  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 8y ago
    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-explained/ https://www.spectrumnews.org/news/link-parental-age-autism-e...
dsfyu404ed 8y ago
I can already see the click-bait headlines: "mosquito bites linked to autism" "outdoor recreation during pregnancy may cause autism" "are children conceived on camping trips more likely to be autistic?
ams6110 8y ago
Mentioning mosquitos, we need to keep in mind that (if the conclusion of the study is true) we traded a small--and at the time not understood--increase in autism for a huge decrease in mosquito-related disease. Millions of people who would have died in childhood are alive thanks to DDT and other insecticides.
- gascan 8y ago
  Yes, and at the time it might have been a good tradeoff- but today we can do better, at least outside the malaria belt.

nigelcleland 8y ago

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.

grecy 8y ago
I'm re-reading it now. If you loved it, checkout Ishmeal by Daniel Quinn[1]. It's a fascinating way to further understand what we're doing to the planet and why we are able to so easily justify it. [1] https://amzn.to/2MOZciN https://amzn.to/2MOZciN
gadders 8y ago
>>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-millions-of-people-their-lives https://www.thedailybeast.com/how-rachel-carson-cost-million...
- gowld 8y ago
  That's a controversial claim. https://en.wikipedia.org/wiki/DDT#Criticism_of_restrictions_on_DDT_use https://en.wikipedia.org/wiki/DDT#Criticism_of_restrictions_... 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.

nerdponx 8y ago

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.

superpie 8y ago
Has anyone found the full text of this tax funded study published anywhere that's not charging $35 to read it?
- nerdponx 8y ago
  I have the same complaint. If you aren't affiliated with university library, or for some reason you aren't willing to use Sci-Hub, then probably not.
  - bjourne 8y ago
    Why would you not be willing to use scihub? http://sci-hub.tw/10.1176/appi.ajp.2018.17101129 http://sci-hub.tw/10.1176/appi.ajp.2018.17101129

dvfjsdhgfv 8y ago

> 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 8y ago
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 8y ago
  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-think-that-cell-phones-are-safe-a-special-investigation/ https://www.thenation.com/article/how-big-wireless-made-us-t...
  - bluGill 8y ago
    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.

dreamcompiler 8y ago

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

fallingfrog 8y ago

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 8y ago
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 8y ago
  This isn't a DDT-Autism link, it's a preliminery curiosity in the data that is motivating further research.
hyperpape 8y ago
DDT is very stable and bioaccumulates. I don't know how much exposure a woman giving birth in the 2000s would have relative to earlier years, but I don't think you can assume it's that low. My instinct is that based on the study's moderate effect size and the lack of strong birth order effects or links to breastfeeding in autism, this effect can't explain the dramatic rise in autism diagnoses in the past several decades. I'm not a scientist, so take this with a grain of salt.
chimeracoder 8y ago
> 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. Not necessarily. The effects could be transgenerational (there's already precedent for that with other substances and executive function disorders, of which ASD is one[0]). Even the rise in autism cases isn't necessarily evidence against this link, because the ability to diagnose people 30+ years ago was dramatically different from our ability to properly diagnose people today. [0] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3931498/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3931498/

scott_s 8y ago

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.

kosma 8y ago

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

tboyd47 8y ago
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.

mrfusion 8y ago

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

colanderman 8y ago
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.html https://www.cdc.gov/zika/prevention/prevent-mosquito-bites.h...

madrox 8y ago

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.