Research Linking Microcephaly (small head size)
to Pesticides & Chemicals - Consideration for Zika

by Richard Pressinger (

  Recently, doctors in Brazil published a paper suggesting the Zika virus was linked to pesticide use in the counties where the virus was most common. To determine if exposure to chemicals and head size has been studied previously, we are undergoing a medical journal search on this topic. As the human brain grows at 4,000 cells per second beginning the 4th week of pregnancy, it is important to understand to what extent chemicals can damage or compromise this process. As can be seen below, there are in fact, a number of studies showing how the growth of the brain can affected resulting in slower growth and microcephaly. Links to the original articles are also given for confirmation and further analysis.

Elevated Brain Damage & Microcephaly
After Exposure to Common Mosquito Control Pesticide

Source: Neurochemical Research, 19(5):569-574, 1994

nerve damage - naled pesticideMicrocephaly is a medical condition in which the brain is considerably smaller than normal, resulting in decreased intelligence and behavior problems. Although the research described here is not directly linked to living near agriculture, it does show how common pesticides can cause microcephaly. The chemical trichlorfon is an ingredient in the commonly used mosquito control pesticide dibrom (also referred to as naled).  

The photograph above shows the brain of a normal guinea pig (left) and the brain of a guinea pig that was exposed to the chemical trichlorfon found in the mosquito control pesticide dibrom (right). In this current study, the chemical trichlorfon was found to cause a - severe reduction - in brain weight and shape of test animals.   The timing of exposure appeared to be the key factor in determining whether observable brain damage was apparent.  Brain damage was observed when guinea pigs were exposed to a non-lethal dose of the pesticide between 42-46 days of gestation at levels of 15 mg/kg. Scientists say this time period correlates with the brain growth spurt period for the animal.

The powerful neurotoxic nature of the pesticide was further emphasized when the scientists found that these brain abnormalities did not occur when animals were exposed to the other pesticides tested - soman - TOCP and ethyl-trichlorfon.

Scientists concluded by stating they suspect the nervous system abnormality occurred due to direct damage to DNA at a time when the animals' repair systems are not developed.

CHEM-TOX COMMENT:  The fact that this study shows neurological damage can easily occur in animals (who are often less sensitive than humans to harmful neurological effects) is enough to warrant serious re-evaluation regarding the use of this toxic chemicals over populated areas.

University of Oslo, Institute of Biology
Department of Molecular Cell Biology, Oslo, Norway
Norwegian Defense Research Establishment
Division for Environmental Toxicology, Kjeller, Norway


Microcephaly after Oral Exposure
to Organophosphorus Pesticides

Source: Human Experimental Toxicology, 27(3):231-40, 2008

In this study, litters of mice were exposed to high and low concentrations of organophosphate pesticides before mating. When looking at the offspring of exposed mice, it was found they had higher rates of malformations - including defects of the ears, eyes, jaws, brain and tongue. They also had increased rates of cataracts, microcephaly (small brain) and anencephaly (no brain).

Gomes J, Loykd OL, Hong Z.
Faculty of Health Sciences,
University of Ottawa, Ottawa, Ontaia, Canada

  Microcephaly after Exposure to Rat Pesticide Warfarin



More articles to be published soon.

Thank you,