Birth defects:

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Numerous studies link birth defects to infants’ exposure to organophosphates while in the womb. One such study links birth defects in the brain, ears, eyes, heart, and genetalia to mothers’ exposure to chlorpyrifos during their pregnancy. These mothers were exposed to chlorpyrifos in a domestic context when it was still available for home use. However, chlorpyrifos in an agricultural context would almost certainly have similar effects on infants. Most studies on this topic only identify organophosphates as the cause of birth defects. Little is known about the exact mechanisms of disruption.

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Neurobehavioral effects:

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Because organophosphates target the nervous system, specifically the central nervous system, they can affect cognition and sensory capabilities. These responses are classified as neurobehavioral.

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A study published in 2017 monitored adolescent farm workers in Egypt for two years. They used a battery of neurobehavioral tests to assess the subjects’ memory, attention span, motor control, and visual abstraction abilities. They also monitored bio markers, compounds in the body indicative of organophosphate exposure over the sampling period. The results found higher levels of biomarkers in subjects with higher exposure, and overall decreased neurobehavioral performance in subjects with higher exposure. In addition to this correlation, researchers found that the subjects exposed to a higher concentration of the pesticide showed less improvement (from a learning effect) as they repeated the tests over the study. This is just one example of a plethora of studies with the similar findings. In fact, a review published in 2016 found that 24 out of 33 studies found an association with occupational exposure to organophosphates with neurophysical alterations which lead to neurobehavioral effects.  

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Another study published in the Journal of Neurotoxicology found that rats repeatedly exposed to chlorpyrifos demonstrated had altered functionality of the serotonergic nervous system and exhibited behavior associated with animal models of depression and anxiety.

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After reviewing recent literature it is clear that exposure to organophosphates results in neurobehavioral effects; however, most studies have not been able to identify the biological mechanisms for these abnormalities. This is due in part to the complexity of the brain and difficulty of observational studies on human subjects.

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Toxicity is age dependent:

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Intuitively, it makes sense that a toxin will have a larger effect on brains and bodies that are not fully developed. Numerous studies have found this to be the case with organophosphates.

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One such study was done in which rats of different ages were given oral doses of chlorpyrifos. Researchers found that the minimum dose that resulted in behavioral and chemical changes was five times greater in adult rats than in young rats (17 days old). Previous studies show that rats detoxify organophosphates with two classes of enzymes--carboxylesterases and A-esterases. It has also been found that young rats are deficient in both these enzymes.

 

This is a proposed reason that chlorpyrifos is significantly more toxic to young rats. The rat is the organism most often used to model human responses to pesticides. This method allows for more higher degree of experimental control and consistency than could be achieved by working with humans due to ethical limitations. However, results found with rats cannot be fully extrapolated to humans.  In any case insight to a mammal’s response to chlorpyrifos is integral to our understanding of how the pesticide affects humans.

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The effects are not equally distributed:

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The scientific findings clearly demonstrate that exposure to organophosphates is detrimental to human health. However, an analysis of the pesticides’ effect on humans would be incomplete without consideration of whom in the population is affected. The majority of studies conducted on human subjects monitor subjects in rural areas of countries in the global south--notably Ecuador, Thailand, and Egypt. This disproportionality in exposure levels is a demonstration of how worth is awarded to human lives disproportionally based on colonial power structures.

 

Historically colonized groups continue to be not only marginalized, but systematically exploited by groups that were historically colonizers. The fact that workers’ health is of little concern, and this exposure is in the context of the global agricultural system, which thrives on systematic exploitation, makes pesticide exposure a classic embodiment of colonial power dynamics. Clearly, this social dynamic exists on a global scale, but it is also very prevalent on a national scale in the US. The fact that the pesticide was banned for home use years ago, yet is still approved for agriculture is indicative of the way in which agricultural workers are regarded as less valuable than others in our national population. 

 

One literature review found that the United States and Thailand accounted for over half of the 25,000,000 reports of pesticide poisonings globally. This demonstrates that pesticide exposure is prevalent not only in countries of the global south, but also in the US. The EPA’s recent decision to reject the ban on chlorpyrifos will only solidify structurally oppressive power dynamics. Action against this decision appeals not only to ethical obligation to human life, but also to a utilitarian ethical standpoint. Banning this harmful substance will improve the overall wellbeing of our population.

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