Organophosphates are among the most commonly used classes of pesticides in the United States, despite mounting evidence linking prenatal exposure to the chemicals to poorer cognition and behavior problems in children.
A new study led by University of California, Berkeley, researchers is one of the first to use advanced brain imaging to reveal how exposure to these chemicals in the womb changes brain activity.
The study, which appeared this week in the journal Proceedings of the National Academy of Sciences, used functional near-infrared imaging (fNIRS) to monitor blood flow in the brains of 95 teenagers born and raised in California’s Salinas Valley, where agricultural spraying of pesticides is common.
Compared to their peers, teenagers estimated to have higher levels of prenatal exposure to organophosphates showed altered brain activity while performing tasks that require executive control, the study found.
“These results are compelling, because they support what we have seen with our neuropsychological testing, which is that organophosphates impact the brain,” said Sharon Sagiv, associate adjunct professor of epidemiology at UC Berkeley and lead author on the study.
The teenagers were part of the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS), a longitudinal study examining the effects of pesticides and other environmental toxins on childhood development. The study was initiated by UC Berkeley investigators more than 20 years ago. Previous CHAMACOS work has linked prenatal organophosphate exposure with attention problems and lower IQ in children.
In the current study, the researchers used fNIRS to measure brain activation while teens ages 15 to 17 engaged in a variety of tasks requiring executive function, attention, social cognition and language comprehension.
The fNIRS technique uses infrared light to monitor blood flow in the outer regions, or cortex, of the brain. It provides similar information as functional magnetic resonance imaging (fMRI), but only requires a small cap of infrared light sources, rather than massive MRI tube, making it a more affordable and portable choice for research studies.
The researchers also used data from the California Pesticide Use Reporting program, which documents when and where agricultural pesticides are sprayed, to estimate their residential proximity to organophosphate application during pregnancy.
They found that teens with higher prenatal organophosphate exposure had less blood flow to the frontal cortex when engaged in tasks that test cognitive flexibility and visual working memory, and that they had more blood flow to the parietal and temporal lobes during tests of linguistic working memory.
“With fNIRS and other neuroimaging, we are seeing more directly the potential impact of organophosphate exposure on the brain, and it may be more sensitive to neurological deficit than cognitive testing,” said Brenda Eskenazi, Professor of the Graduate School at UC Berkeley and senior author of the study.
Little is known about the relationship between pesticide exposure and the brain, so it’s not clear why organophosphate exposure is associated with lower brain activity for some tasks and higher brain activity for others.
However, similar patterns have been observed in other conditions affecting the brain, including Type 1 diabetes, Parkinson’s and Alzheimer’s, said Allan L. Reiss, the Howard C. Robbins Professor of Psychiatry and Behavioral Sciences and a professor of radiology at Stanford University and co-author of the paper.
“The brain has a remarkable ability to utilize compensatory mechanisms to counteract long-term insults,” Reiss said. “Higher activation may represent the recruitment and utilization of extra neural resources to address functional inefficiency related to a long-term insult, and lower activation, then, could be related to the eventual failure to recruit these resources after continued exposure or disease exhausts the brain’s ability to bring compensatory responses online.”
In the future, the team plans to repeat the brain imaging experiments on the more than 500 other participants in the CHAMACOS study to test if the associations hold.
Co-authors of the paper include Jennifer L. Bruno and Joseph M. Baker of Stanford University and Vanessa Palzes, Katherine Kogut, Stephen Rauch, Robert Gunier and Ana Maria Mora of UC Berkeley.
This work was supported by the National Institutes of Health (NIH) under grants UG3 OD023356, P01ES009605, R01 ES015572, T32 MH019908, K99 HD092883 and K99 HD092883; the US Environmental Protection Agency (EPA) under grants RD 83171001 and RD 83451301; the Stanford Maternal and Child Health Institute; and a gift from the Albert Yu and Mary Bechmann Foundation.
hughperman on August 28th, 2019 at 08:21 UTC »
I will be the sceptical voice. This is the science section and everyone seems to be jumping on the popular opinion bandwagon without reading the paper.
1) When they applied multiple comparisons correction, their results disappeared totally. They say it's because the FDR method they used was inappropriate; I work with this sort of data and there are other methods that can be applied, but usually you will see something even with a over-zealous correction (also FDR isn't that stringent). 2) There was not a single mention in methods or results of measuring actual test performance against their inferred pesticide exposure variable. I find that pretty crazy considering the whole study is about changes in the brain during said tests. They then go on to say in the discussion that there was no associated changes - I find it a little disingenuous to test it and not report this in the methods or results. 3) On the plus side, covariates applied are generally sensible, and there was no change adjusting for family poverty, which was my first question. The child's years of education might have been a useful one to add. 4) Not much discussion about whether these are sensible changes to observe. This type of data is rife for misinterpretation - things go up and down and you have to interpret whether high is good or bad and whether it's your baseline or task that's causing the difference. The authors hand-wave around this a bit, but from experience this often means authors are stretching to explain the changes.
These results are very fragile. It would take a lot more data to make any concrete conclusions, and long-term follow-up to see if there is any actual effect of the brain activation changes - even if they continue to be supported by evidence, there are no behavioural changes found here, so it may not matter at all.
MittonMan on August 28th, 2019 at 07:13 UTC »
So to be clear, this study addresses direct contamination of pesticide (in vicinity around farms) and not fruits consumed? Because as far as I know most pesticides have half lives that should render them moot by the time of consumption.
mvea on August 28th, 2019 at 04:43 UTC »
The title of the post is a copy and paste from the photo caption and second paragraph of the linked academic press release here:
Journal Reference:
Sharon K. Sagiv, Jennifer L. Bruno, Joseph M. Baker, Vanessa Palzes, Katherine Kogut, Stephen Rauch, Robert Gunier, Ana M. Mora, Allan L. Reiss, Brenda Eskenazi.
Prenatal exposure to organophosphate pesticides and functional neuroimaging in adolescents living in proximity to pesticide application.
Proceedings of the National Academy of Sciences, 2019; 201903940
Link: https://www.pnas.org/content/early/2019/08/20/1903940116
DOI: 10.1073/pnas.1903940116
Significance
Little is known about the neural dynamics underlying previously reported associations of organophosphate (OP) pesticides with adverse neurodevelopment. We used functional near-infrared spectroscopy (fNIRS) to examine cortical brain activation in relation to residential proximity to OP use during pregnancy among 95 adolescents enrolled in a longitudinal birth cohort. We found that prenatal OP exposure was associated with altered brain activation during tasks of executive function. We also found sex differences for OPs and brain activation during a language comprehension task. Use of fNIRS, an inexpensive and easily accessible technology, enhances our efforts to assess the impact of environmental exposures on brain function.
Abstract
We have reported consistent associations of prenatal organophosphate pesticide (OP) exposure with poorer cognitive function and behavior problems in our Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS), a birth cohort of Mexican American youth in California’s agricultural Salinas Valley. However, there is little evidence on how OPs affect neural dynamics underlying associations. We used functional near-infrared spectroscopy (fNIRS) to measure cortical activation during tasks of executive function, attention, social cognition, and language comprehension in 95 adolescent CHAMACOS participants. We estimated associations of residential proximity to OP use during pregnancy with cortical activation in frontal, temporal, and parietal regions using multiple regression models, adjusting for sociodemographic characteristics. OP exposure was associated with altered brain activation during tasks of executive function. For example, with a 10-fold increase in total OP pesticide use within 1 km of maternal residence during pregnancy, there was a bilateral decrease in brain activation in the prefrontal cortex during a cognitive flexibility task (β = −4.74; 95% CI: −8.18, −1.31 and β = −4.40; 95% CI: −7.96, −0.84 for the left and right hemispheres, respectively). We also found that prenatal OP exposure was associated with sex differences in brain activation during a language comprehension task. This first functional neuroimaging study of prenatal OP exposure suggests that pesticides may impact cortical brain activation, which could underlie previously reported OP-related associations with cognitive and behavioral function. Use of fNIRS in environmental epidemiology offers a practical alternative to neuroimaging technologies and enhances our efforts to assess the impact of chemical exposures on neurodevelopment.