02
Jul
Endocrine Disrupting Chemicals, Including Pesticides, Have a Multi-Generational Impact on Commercially Beneficial Inland Silverside Fish
Image by Rickard Zerpe, Hardyhead Silverside (Atherinomorus lacunosus) (Photo: Hardyhead Silverside…/cc/flickr)
(Beyond Pesticides, July 2, 2020) Exposure to low levels of endocrine-disrupting chemicals commonly in waterways, including pesticides, can impact future generations of major commercial fish, despite no direct exposure to the chemicals, according to research published in the journal Frontiers in Marine Science by Oregon State University (OSU) researchers. Many studies assess the acute or chronic health implications associated with endocrine disruptors on a single generation but lack information on multi-generational impacts that can provide vital information on the fundamental survivability or fitness of many species. This study highlights the significance of understanding the implications of endocrine disruptors, even at low levels of exposure, as parental exposure can have adverse epigenetic consequences for future generations. Kaley Major, a Ph.D. fellow at Oregon State University (OSU) and lead research author, explains, “What t[his] gets at is something your grandparents may have come into contact within their environment can still be affecting the overall structure of your DNA in your life today.”
Endocrine disruptors are xenobiotics (i.e., chemical substances like toxic pesticides foreign to an organism or ecosystem). Past research shows exposures to endocrine-disrupting chemicals can adversely impact human, animal—and thus environmental—health, by altering the natural hormones in the body responsible for conventional fertile, physical, and mental development. However, this study looks at the implications of low levels of endocrine disruptors in a multi-generational platform, showing an epigenetic relationship between pesticide exposure and disease. Susanne Brander, Ph D., professor and aquatic toxicologist at OSU’s Department of Fisheries and Wildlife, notes the importance of understanding the consequence of exposure to endocrine disruptors on a day-to-day basis, “It’s really important to understand how animals can deal with stress in the environment, particularly when we are introducing new stressors on a daily basis.”
Researchers examine the multi- and trans-generational impacts on early life exposure to endocrine disruptors and their alteration of the genome in inland silversides (Menidia beryllina) fish, a staple bird prey and commercially valuable fish. The chemicals under investigation are emerging endocrine disruptors of concern: the pyrethroid insecticide bifenthrin; the synthetic progestin levonorgestrel; commonly detected synthetic estrogen (ethinylestradiol); and a synthetic androgen (trenbolone). Scientists added the analogous of a few drops of each endocrine disruptor in an Olympic-size swimming pool with silversides to mimic low-level exposure in the natural environment. Previous research demonstrates endocrine disruptors’ impact on DNA methylation (i.e., the process of adding a methyl group to a DNA molecule). Therefore, researchers tracked methylation for changes in gene expression and organism development using bisulfite sequencing, over 21 months in three generations.
All three generations of fish demonstrate multi- and trans-generational inheritance of altered DNA methylation patterns and epigenetic dysfunction in comparison to the control group. Researchers observe an enrichment in biological processes and pathways involving carcinogenesis or cancer formation in fish. Additional analysis shows methylation differs in prospective endocrine responsive genes upon exposure to each endocrine-disrupting chemical, within each generation.
Inheritance of genetic dysfunction relating to hereditary influence on gene expression is a familiar phenomenon. Various studies note that adverse genomic alterations can phase down to future generations. However, the inheritance of epigenetic dysfunction relating to non-genetic influence (i.e., exposure to endocrine-disrupting chemicals like pesticides) on gene expression poses just as much of a risk to future generations. As far back as 15 years ago, a Washington State University study linked pesticide exposure to multi-generational impacts on male fertility in rodents. More recently, a plethora of research links pesticide exposure to endocrine disruption with transgenerational effects. According to multiple studies, exposure to the weed killer glyphosate (patented as an antibiotic) changes the bacterial composition of the gut microbiome in cattle, rodents, and honey bees. Researchers also found that glyphosate exposure has adverse multi-generational effects, causing negligible observable impacts on pregnant rodents, but severe effects on the two subsequent generations, including reproductive (prostate and ovarian) and kidney diseases, obesity, and birth anomalies. The emerging pesticide of concern, bifenthrin, disrupts normal reproductive function in rodents, causing alterations to the gene expression for hormone synthesis. New findings suggest exposure to the pesticide atrazine causes multi-generation resistance to the chemical in wasps by altering gut bacteria composition. Even banned pesticides like DDT still impact current and future generations, as DDT (and subsequent metabolites) can cause multi-generational cancer, multi-generational obesity, and generational reproductive abnormalities via endocrine disruption. Moreover, chemical byproducts made during the pesticide manufacturing process, such as dioxin, have multi-generational consequences on reproductive health.
This research finds clear evidence of epigenetic alteration to silverside fish offspring’s genome from limited exposure to endocrine-disrupting chemicals. The consistent patterns of methylation across the three generations show a relationship between methylation and epigenetic dysfunction. Scientists in the study believe that the observable, generational methylation patterns affect gene expression associated with distorted sex ratios, a reduction in hatching, and developmental defects in silversides. Implications for future research include a better understanding of what methylation markers mean and how these markers determine the effect of pollutants on the evolution or fitness of inland silversides. Dr. Susanne Brander states, “Our research helps show what animals do to respond to these changes and how quickly they can respond to them. That’s going to help us understand our impact on the environment in the long run.”
It is imperative to comprehend the impacts endocrine-disrupting chemicals have on aquatic organisms, like silverside fish, to help researchers understand the implications associated with exposure. However, environmental pollution from endocrine disruptors like pesticides is specifically concerning as the Trump administration is dismantling many environmental regulations, undermining scientific data, and upholding agrochemical company interests above ordinances. The administration reduced environmental safeguards in federal water by permitting offshore aquaculture. The administration already fails to accurately monitor water sources as exposure atrazine from waterways is higher in the Midwest during spring. Despite this, the administration has waived the requirement of the multinational chemical company Syngenta-ChemChina to continue monitoring Midwest waterways for the presence of the weed killer atrazine, through 2020. The input of glyphosate into the water ecosystem leads to a loss in ecosystem biodiversity and productivity. Furthermore, Chicago-based black women who consumed more glasses of tap water per day had residues of the DDT metabolite (DDE’) in their system. With this evidence, it is apparent that the federal government should implement strong safeguards that avoid harmful impacts of pesticide exposure on the current and future generations of humans and animals.
Beyond Pesticides believes that we must mitigate the multi-generational impacts pesticides pose on human and animal health. Adopting regenerative-organic practices and using least-toxic pest control can reduce harmful exposure to pesticides. Public policy should advocate for formidable safeguards on the agrochemical industry that ensure the terrestrial and aquatic environment are safe from chemical hazards. In doing so, we can shift away from unnecessary reliance on pesticides. For more on how to make that reality possible, check out our Tools for Change page and keep well-informed with our Action of the Week—tell Congress to save our oceans. Learn more about multi-generation impacts of pesticides on our health via Beyond Pesticide’s journal Pesticides and You. Additionally, learn more about the effects of pesticides on human health by visiting Beyond Pesticides’ Pesticide-Induced Diseases Database. This database supports the clear need for strategic action to shift away from pesticide dependency.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Sources: Frontiers in Marine Science, Oregon State University
