We are very grateful to Dr. Kassotis for providing this letter and his expertise to the Dover city council and school board on the issue of pesticide use and public health.
To Whom It May Concern:
I was informed regarding the upcoming resolution to restrict pesticides on city property and wanted to reach out. I grew up and went to college not far from Dover, in the greater Keene area, and often spent time in Dover growing up. Following college, I pursued a doctoral degree and now work as an Endocrine Toxicologist at Duke University in Durham, NC. In this role, I study endocrine disrupting chemicals, which we define as chemicals or mixtures of chemicals that can interfere with our body’s chemical messenger system (the endocrine system) in any way. This is often through mimicking or inhibiting the action of hormones, the chemical messengers that our body uses to regulate a number of developmental and maintenance processes throughout the body. This includes wide-ranging processes including but not limited to fertility, metabolism, neurological function (IQ, behavioral disorders), cell proliferation (and cancer incidence), pubertal development, immune function, and others.
I’m sure that your board is aware of much of the research surrounding the use and application of pesticides, and conventional versus organic agriculture. As my expertise is in toxicology, I’d like to communicate some of the toxicological and human health data surrounding pesticide application and use. First, there is a wealth of available information correlating pesticide application and adverse health outcomes in local children. Importantly, these are not necessarily causative, but many (most notably including neurodevelopmental outcomes) have been replicated by many different labs in different regions of the US and abroad. Second, as my research interests include environmental mixtures, I’d like to spend some time describing the complexities and concerns surrounding widespread pesticide use. I don’t want to weigh this down with numerous scientific papers, so I’ve tried to select a few specific papers that review a broad amount of the existing literature on the topic and/or highlight specific points. I’m happy to provide further research if you’re interested in hearing more on a particular topic.
The associations between pesticide application and adverse neurodevelopmental health outcomes in children have been well established. I’ve attached a systematic review of the literature on this topic for organophosphate pesticides 1. Of the 27 scientific studies reviewed therein, 26 of the 27 reported significant impacts on child neurodevelopment. This literature is particularly strong as a large number of these studies were longitudinal, measuring exposure of the mothers prior to birth and then following the health of their children throughout life. These adverse health outcomes included impacted cognition (decreased IQ, working memory deficits, etc.), inhibited motor development (reflexes, etc.), and increased behavioral issues (most notably attention problems, but also autistic behaviors). I think what this review does well is summarize a broad range of studies spanning exposure levels. By that I mean, these adverse effects were demonstrated in children born to parents who received occupational exposure (applying the pesticides, working in agriculture), residential exposures, para-occupational exposures (contact with an occupationally exposed person), and background environmental exposures. This highlights that these outcomes are not restricted to high exposure levels, but that residential and general environmental exposure is sufficient to promote this same spectrum of adverse effects in some cases. While this review covered just one class of pesticides, many of these neurodevelopmental effects are observed across pesticide classes. For example, in another study, increased risks of autism spectrum disorder and developmental delays occurrence were observed near organophosphate, pyrethroids, neonicotinoids, and carbamate pesticide applications 2.
Notably, dietary interventions that switch conventional produce for organic produce succeed in reducing exposure of children to multiple pesticides. Analyses of pesticide residue data demonstrate that organically grown foods generally contain about one third as many pesticide residues as conventionally grown produce, and one half as many residues when compared to integrated pest management system produce. Non-organic options are also much more likely to contain multiple pesticide residues on individual items, increasing exposure to a broader array of chemicals. I’ve included one article that highlights some of the dietary intervention research that has been performed. These clearly demonstrate that switching standard conventional produce to organic reduced organophosphate pesticide levels in the urban/suburban children assessed 3. Similar studies have demonstrated reductions in pyrethroids, neonicotinoids, and other classes of agricultural pesticides.
This leads into my last point, which is the issue of chemical mixtures. Conventional produce increases exposure to a wider range of chemicals, adding to an array of pesticides used for other land management purposes. While each individual chemical may be applied within federal exposure limits, many promote effects through similar biological pathways. What this means is that chemicals can have “additive” effects, where a combination of chemicals can cause an effect even when each individual chemical is present below levels that elicit any measurable effects independently. In toxicology, we term this “something from nothing”, and it has been characterized for a number of biological pathways that many pesticides utilize. I’ve attached a recent article demonstrating these effects. In brief, the researchers tested a mixture of five common environmental pollutants, effecting four different biological pathways, and found that they acted together to inhibit egg production in fish in an additive manner 4. Even despite differing biological mechanisms, they acted in tandem to increase the magnitude of the effect. This raises real concerns for conventional pesticide application, where we have a multitude of different chemicals applied and occurring at low levels in tandem. It also represents an unfortunate complexity to pesticide research, where research on chemicals such as glyphosate has been complicated by different toxicity outcomes for the pure chemical versus the commercial chemical mixture sold on shelves.
In closing, I’d like to recommend to the board that it is in the interest of public health to reduce exposure to pesticide mixtures where possible. There is abundant data suggesting adverse impacts of numerous pesticides on neurodevelopmental outcomes in children. Implementing a safer organic turf and land management program and reducing or eliminating agricultural uses where possible is in the interest of community health, and I hope these factors will be taken into account during consideration of these resolutions.
Please feel free to contact me with any questions or clarifications.
Christopher D. Kassotis, Ph.D.
Postdoctoral Research Scholar
Nicholas School of the Environment
1 – Neurodevelopmental effects in children associated with exposure to organophosphate pesticides: A systematic review.
PDF: Muñoz-Quezada et al 2013 organophosphate pesticide systematic review
2 – Neurodevelopmental disorders and prenatal residential proximity to agricultural pesticides: the CHARGE study.
PDF: Shelton et al 2014 residential proximity pesticides and neuro outcomes CA
3 – Dietary intake and its contribution to longitudinal organophosphate pesticide exposure in urban/suburban children.
PDF: Lu et al 2008 dietary intervention and organophosphate pesticides in children
4 – The consequences of exposure to mixtures of chemicals: Something from ‘nothing’ and ‘a lot from a little’ when fish are exposed to steroid hormones.
PDF: Thrupp et al 2018 something from nothing five pollutants in fish