ENVIRONMENTAL NEURODEVELOPMENTAL RISK IN THE AGRICULTURAL MIDWEST

What pesticide research means for families living across the Corn Belt

Pesticides and herbicides are familiar terms in most households across the United States. People use them for various reasons, typically for treating their backyards, gardens, and homes from pesky intruders. Many people also know they are used large scale in agriculture. But, what many people do not know is their impact on human wellness, especially when repeated exposure is considered. Today, we will explore exposure during pregnancy, infancy, toddlerhood, and the preschool years and how that may intersect with the developing brain, behavior, attention, social function, and regulation of children.

Compelling Highlights: (TL;DR)

The emphasis is the convergence across different forms of evidence:

• California application records connect agricultural proximity during pregnancy and infancy with autism outcomes in a large population. [8]

• USDA and USGS data establish the immense scale and continuity of pesticide-treated acreage across the Corn Belt. [10-13]

• Iowa studies document pesticides moving from fields and work practices into homes, dust, children’s rooms, and children’s urine. [1-2]

• Preschool wristbands capture pesticide mixtures across ordinary home and child-care life, including higher exposure near fields. [16]

• Children’s own biomarkers during ages two through six are associated with motor, social, attention, and behavioral outcomes. [3-5]

• Postnatal PM2.5 exposure during ages two through four is associated with measurable behavior and cognitive differences. [6]

• Mechanistic research identifies plausible gut, immune, metabolic, and neural pathways that can connect exposure with developmental function. [9]

The Evernorth Experience

As Evernorth’s founder, I approach this research through both evidence and lived family experience. Both of my children have faced different health, sensory, allergic, and developmental challenges. This is something I have both researched extensively, as well as experienced firsthand with my own child having spent prenatal and two years postnatal in the Midwest region of the United States. 

My child's exposures and experiences as well as neurodevelopment responses are meant merely as context and are not part of any official case study that will be presented.

Todays Exploration

Can repeated pesticide and agricultural-pollution exposure during critical developmental windows influence neurodevelopmental likelihood, symptom burden, attention, behavior, motor or social development, and a child’s capacity to regulate? 

Pediatric guidance recognizes pesticides as a broad class of toxicants capable of producing acute and chronic health effects. Depending on the compound and exposure, concerns can include irritation, respiratory effects, abnormal neurodevelopment, altered growth, endocrine disruption, and childhood disease risk. Now, it is also being studied as a neurological and neurodevelopmental concern. [14]

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California made the pesticide concern measurable

California's detailed pesticide-use reporting requirements allowed researchers to connect particular agricultural compounds, application locations, timing, and health records with unusual precision. The 2019 BMJ population-based study included 2,961 children with autism, including 445 with intellectual disability, and nearly 30,000 matched controls. Researchers estimated agricultural pesticide applications within 2,000 meters, approximately 1.25 miles, of the mother’s residence during pregnancy and the child’s first year. [8]

Prenatal proximity was associated with increased autism odds for glyphosate, chlorpyrifos, diazinon, malathion, avermectin, and permethrin. The adjusted estimates for autism overall were approximately 10% to 16% higher, with larger associations for autism accompanied by intellectual disability. First-year exposure was also associated with autism with intellectual disability for several compounds. [8]

In other words, an odds ratio of 1.10 means the exposed group had 10% higher odds relative to the comparison group after the study’s adjustments. These are population-level associations, and their importance comes from the size of the study, the detailed application records, the repeated pattern across several pesticides, and the vulnerability of exposure of both prenatal and postnatal.

Why a California study is relevant to the Midwest

California state regulations require in-depth reporting information, making it a genuine approach to understand how exposure to certain chemicals and toxicants can affect children, whether in California or the Midwest. One could even argue that the outcome could be potentially more significant in the Midwest when you account for the increased annual pesticide use in that region.

The exact California risk estimates cannot simply be pasted onto Kansas, Iowa, or Nebraska, because crops, weather, application practices, housing, and populations differ. Nonetheless, the study remains highly relevant when it is paired with separate evidence showing that the Midwest has enormous agricultural acreage, extensive pesticide application, household transport, and even measurable exposure inside children's bodies, themselves.

The Exposure Reality

USDA’s 2021 corn survey covered states representing 92.1% of U.S. corn acreage. Iowa, Illinois, Nebraska, Minnesota, South Dakota, Kansas, Indiana, North Dakota, Wisconsin, and Missouri led the list. Herbicides were applied to 96% of planted corn acres. Atrazine was applied to 65%, and glyphosate isopropylamine salt to 41%. Kansas alone accounted for 5.7 million planted corn acres in the survey. [10]

USDA’s soybean survey likewise found herbicides applied to 96% of planted soybean acres, with production concentrated across many of the same Midwestern and Great Plains states. A longer USDA analysis identified corn as the nation’s top pesticide-using crop and found that corn and soybeans together accounted for more than three-fifths of pesticide pounds applied to the 21 major crops analyzed in 2008. USGS maps show the same broad geographic reality: pesticide use is distributed across a vast, continuous Corn Belt rather than confined to isolated fields. [11-13]

The most important study for Midwest families comes from Iowa. The NIH Agricultural Health Study found chlorpyrifos, glyphosate, and 2,4-D in household dust in most sampled Iowa homes. Farm homes generally had higher residues. Pesticides were detected more often in carpet dust than in air or on hard surfaces, and residues reached children’s bedrooms and play areas. Tracked dirt and work clothing were associated with higher concentrations of some agricultural chemicals. [1]

A separate Iowa study measured urinary pesticide concentrations in 117 children and their parents. Children in farm households had significantly higher atrazine metabolite levels than children in nonfarm households. When fathers had recently applied atrazine or chlorpyrifos, their children had significantly higher urinary concentrations of those chemicals. Among farm children, chlorpyrifos measured in urine was also associated with chlorpyrifos in household dust. [2]

This sequence confirms a documented pathway beginning with a chemical applied agriculturally, carried or deposited indoors, stored in dust, and then measured inside a child. Therefore, we can say with certainty that these chemicals and known toxicants are being spread throughout the Midwest region of the country and found within the bodies of children.

Another study in the Midwest is known as the preschool wristband study. This study made the same idea visible in ordinary daily life. One hundred twenty-five preschool-age children wore silicone wristbands that collected chemicals across home and child-care environments. Multiple insecticides were commonly detected. Exposure was higher near agricultural fields and in counties with greater pesticide use. The most concerning element of this study was that ordinary handwashing and routine cleaning did not consistently remove the compounds from hands. [16]

Of course, handwashing remains useful, important, and necessary. But, the findings highlight why hygiene alone may not be enough when air, dust, clothing, shoes, treated surfaces, nearby applications, or outdoor soil continue replenishing the environment.

Why young children receive a different dose from the same environment

EPA’s phrase is direct: children are not little adults. They breathe, eat, and drink more relative to body size; their organs and nervous systems are still developing; and early life contains windows of heightened susceptibility. Their behavior also changes exposure. Crawling, floor play, thumb sucking, and frequent hand-to-mouth or object-to-mouth contact transfer residues from dust, soil, toys, furniture, clothing, and surfaces into the body. [15, 17]

In other words, for a toddler, the internal dose can be much larger, simply because of their size, and their behaviors. The floor is a major contact surface. They spend a lot of time there, playing, and exploring their environment. The carpet is a major culprit, that is a reservoir for an assortment of contaminants. Many possible pathways exist, including a favorite blanket, toy, or even their own hand, or thumb.

The Concern Continues After Birth: ages two through six

Prenatal research is essential, but the evidence of exposure continues beyond the prenatal phase. Several studies measured the child’s own exposure after birth during the exact years when language, motor control, inhibition, social engagement, attention, and emotional regulation are rapidly developing.

At age three, researchers measured urinary TCPy, a chlorpyrifos biomarker, in the child. Higher postnatal TCPy was associated with lower motor and social-development scores. This is exceptionally impactful because the exposure marker came from the child’s own body, making this a direct early-childhood finding. [3]

A longitudinal pyrethroid study measured urinary 3-PBA repeatedly at ages two, four, six, and eight. A doubling of 3-PBA at age two was associated with a 5.2% increase in ADHD symptoms at age six. Measurements at ages four and six were also associated with later ADHD symptoms, and the researchers identified ages two through six as susceptible periods. A separate study of four-year-olds found substantially higher ADHD-like symptom scores in the highest urinary-metabolite group, particularly among boys. [4-5]

These studies establish population-level associations and show that a child’s own internal dose during toddlerhood and the preschool years can correlate with measurable differences in motor development, social development, attention, inhibition, and behavior.

For families already supporting an autistic or otherwise neurodevelopmentally vulnerable child, even a modest additional burden in these domains can matter greatly in daily life.

PM2.5: The childhood finding is postnatal, not prenatal-only

The U.S. multicohort PM2.5 study estimated each child’s residential fine-particle exposure specifically during ages two through four, then evaluated behavior and cognitive performance when the children were ages four through six. Each 2 micrograms per cubic meter increase during ages two through four was associated with a 3.59-point higher Child Behavior Checklist Total Problems score and a 2.63-point lower cognitive score. This finding concerns the child’s exposure after birth. [6]

A separate atmospheric study estimated that ammonia from fertilizer and animal waste contributes about 40% of the Midwest’s PM2.5 burden, approximately four times its average contribution across the contiguous United States. The pediatric study and the Midwest source study are different analyses and should not be merged into one claimed causal estimate. However, read together, they identify a sensitive childhood window and a major agricultural contributor to the region’s particle burden. [6-7]

The gut-brain review helps explain how pesticide exposure could reach behavior

The gut microbiota is the community of microorganisms living within the digestive tract. The gut-brain axis is the two-way communication network linking those microorganisms and their metabolites with the intestinal barrier, immune system, endocrine signaling, metabolism, and nervous system. A 2023 review examined evidence that pesticide exposure during neurodevelopment may disturb this network. [9]

The authors described possible changes involving short-chain fatty acids, lipids, retinol, amino acids, immune regulation, intestinal permeability, metabolism, and neural signaling. The review identifies a credible set of pathways through which repeated exposure could influence neurological and behavioral development in a susceptible child. [9]

What this means for families

The Midwest is not one uniform exposure zone and risk factors vary based on exact field proximity, crop type, application season, wind, home age, flooring, ventilation, water source, nearby livestock operations, and whether farm residues are carried home on clothing or equipment. A family in a city apartment and a family beside treated acreage may both live in Iowa while experiencing different exposure levels.

However, we also recognize that these contaminants do spread and reach homes and people further from application sites through multiple environmental pathways, and for that reason, we share as much information and resources as we can to best inform and support individuals.

Reasonable questions that may provide answers for your family: How close is the home, school, or child-care setting to intensively treated land? Is a private well present? Does the household include agricultural work? Are pesticides used indoors or around the yard? Do carpets and soft furnishings hold settled dust? Is the child frequently on the floor or engaged in thumb sucking and object mouthing? [1-2, 15-17]

What Evernorth concludes

Evernorth interprets this evidence as a strong, cumulative case that agricultural pesticides and related pollutants can reach children during sensitive developmental windows and may influence neurological, developmental, behavioral, and physical wellbeing. We believe in responding proportionately when the exposure pathway is documented, developmental vulnerability is established, and multiple human studies point toward meaningful harm.

For families already supporting autism, developmental delay, attention differences, aggressive behavior, irritability, sleep disruption, sensory dysregulation, or limited social engagement, environmental burden reduction is a way of reducing avoidable strain on systems that may already be working harder to maintain balance.

The question I will end on is: Is precaution reasonable during pregnancy and the first years of life.

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References

[1] Agricultural Health Study / National Institutes of Health. Pesticide Residues in the Homes of Farm Families. Iowa research findings fact sheet. Source

[2] Curwin BD, Hein MJ, Sanderson WT, et al. Urinary pesticide concentrations among children, mothers and fathers living in farm and non-farm households in Iowa. Ann Occup Hyg. 2007;51(1):53-65. doi:10.1093/annhyg/mel062. Source

[3] Guo J, Zhang J, Wu C, et al. Associations of prenatal and childhood chlorpyrifos exposure with neurodevelopment of 3-year-old children. Environ Pollut. 2019;251:538-546. doi:10.1016/j.envpol.2019.05.040. Source

[4] Lee KS, et al. The association of prenatal and childhood pyrethroid pesticide exposure with school-age ADHD traits. Environ Int. 2022;161:107124. doi:10.1016/j.envint.2022.107124. Source

[5] Lee WS, Lee YH, Kim JH, et al. Association between pyrethroid exposure and attention-deficit/hyperactivity disorder-like symptoms in preschool-age children. Environ Res. 2020;188:109739. doi:10.1016/j.envres.2020.109739. Source

[6] Ni Y, Loftus CT, Szpiro AA, et al. Associations of pre- and postnatal air pollution exposures with child behavioral problems and cognitive performance: a U.S. multi-cohort study. Environ Health Perspect. 2022;130(6):067008. doi:10.1289/EHP10248. Source

[7] Vo T, Christiansen M, et al. Impact of Recent Agricultural Ammonia Increases on Fine Particulate Matter Burden over the Midwestern United States. ACS Earth Space Chem. 2024. doi:10.1021/acsearthspacechem.4c00180. Source

[8] von Ehrenstein OS, Ling C, Cui X, et al. Prenatal and infant exposure to ambient pesticides and autism spectrum disorder in children: population based case-control study. BMJ. 2019;364:l962. doi:10.1136/bmj.l962. Source

[9] Yang Y, Zhou S, Xing Y, Yang G, You M. Impact of pesticides exposure during neurodevelopmental period on autism spectrum disorders - A focus on gut microbiota. Ecotoxicol Environ Saf. 2023;260:115079. doi:10.1016/j.ecoenv.2023.115079. Source

[10] U.S. Department of Agriculture, National Agricultural Statistics Service. 2021 Agricultural Chemical Use Survey: Corn. May 2022. Source

[11] U.S. Department of Agriculture, National Agricultural Statistics Service. 2023 Agricultural Chemical Use Survey: Soybeans. May 2024. Source

[12] Fernandez-Cornejo J, Nehring R, Osteen C, et al. Pesticide Use in U.S. Agriculture: 21 Selected Crops, 1960-2008. USDA Economic Research Service. 2014. Source

[13] U.S. Geological Survey. Estimated Annual Agricultural Pesticide Use: national maps and state-level crop-group estimates. Source

[14] Roberts JR, Karr CJ; American Academy of Pediatrics Council on Environmental Health. Pesticide exposure in children. Pediatrics. 2012;130(6):e1765-e1788. doi:10.1542/peds.2012-2757. Source

[15] U.S. Environmental Protection Agency. Children Are Not Little Adults! Updated March 10, 2026. Source

[16] Alkon A, Gunier RB, Hazard K, et al. Preschool-Age Children’s Pesticide Exposures in Child Care Centers and at Home in Northern California. J Pediatr Health Care. 2022;36(1):34-45. doi:10.1016/j.pedhc.2021.09.004. Source

[17] U.S. Environmental Protection Agency. Exposure Assessment Tools by Routes - Ingestion. Updated March 24, 2026. Source

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Evidence scope

This high-level overview translates the strongest findings from the full Evernorth Foundation resource-library. It prioritizes human developmental studies, federal agricultural-use data, federal exposure guidance, and direct Midwestern household or biomarker research. Associations are presented as associations, mechanistic reviews as biological support, and regional evidence as a cumulative case for precaution rather than an individual causal determination.