Developmental Effects

Herbicide exposure has been linked to development and neurological impacts.

The pathway from fertilized egg to the day of birth, and life passages through infancy, childhood and adulthood, can be disrupted, delayed, or driven off course in a variety of ways, with widely varying consequences.

Birth defects are one, often unmistakable example of adverse developmental effects, but many others cannot be diagnosed at birth, and may or may not manifest as an infant grows older.

Most recent pesticide-related developmental research has focused primarily on effects that alter or impair the integrity of the neurological, immune, or reproductive systems. Such impacts encompass a broad array of adverse outcomes:

  • Reduced IQ, behavioral problems, ADHD and autism;
  • Autoimmune diseases and heightened vulnerability to pathogens, cancer, and other factors that can trigger illness; and
  • Abnormal sexual development and reproductive performance and inclinations.

In particular, the now proven, adverse impact of certain insecticides on neurological development has received intense focus by scientists worldwide. Such impacts can lead to reduced IQ and a number of behavioral and learning disabilities.  The rich literature on this topic is accessible via the Heartland bibliography under the tags developmental impacts and neurodevelopmental toxicity.

Recent research has also linked herbicides, and in particular glyphosate, to various neurodevelopmental disruptions leading to adverse birth outcomes like autism.

The largest and most sophisticated population-based study of pesticides and autism was published in the British Journal of Medicine in 2019. The von Ehrenstein et al study was conducted by a University of Southern California led team, and reported a 33% elevation in the risk of autism spectrum disorder coupled with learning disabilities  among children with autism, compared to matched controls.

Surprisingly, living near areas where glyphosate-based herbicides were applied was a more significant a factor in autism than living near where the OP insecticides chlorpyrifos, diazinon, and malathion were applied.

For this reason, the Heartland Study protocol includes annual developmental assessments at ages 1, 2, and 3, and hopefully through age 16 (pending funding), to enable calculation of odds rations linking herbicide exposure levels and autism, as well as other developmental and behavioral outcomes.

In the last decade, scientists have recognized epigenetic-driven adverse health outcomes that can arise from a new type of developmental impact following prenatal exposure to chemicals. The next section briefly introduces the basis for epigenetic changes, and explains why herbicides are now high on the list of possible, population-wide drivers of epigenetic-driven health problems.

Key Science

  • For a recent review of known research on the pesticide exposure and autism and ADHD, see this meta-analysis co-authored by Science Advisory Board (SAB) member Dr. Routt Reigart.
  • This 2017 case study by Dr. William Shaw looks at one farm family whose triplets with autism spectrum disorder all showed elevated urinary glyphosate levels.
  • A team of French scientists found that low-dose pre- and postnatal exposure to glufosinate ammounium herbicide induced autism-like symptoms in mice.
  • For more on why this all matters, see SAB member Dr. Bruce Lanphear’s article “The Impact of Toxins on the Developing Brain,” and this perspective on the economic impacts of neurodevelopmental deficits caused by endocrine-disrupting chemicals like many herbicides.

Low Birthweight & Preterm Delivery

Birth Defects

Epigenetic Impacts

Reproductive Impacts: Conception & Pregnancy

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