(Beyond Pesticides, December X, 2022) Persistent organic pollutants (POPs)—including banned pesticides—present a health risk to humpback whales (Megaptera novaeangliae), according to a study published in Environmental Pollution. Regarding female humpback whales, levels of POPs in blubber are higher in juveniles and subadults than in adults, primarily from the transference of contaminants from the mother to her calf.
Organochlorine compounds (OCs), such as organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs), are well-known persistent organic pollutants. The international Stockholm Convention treaty (signed by 152 countries, but not the U.S.) banned these primary pollutants of concern (UNEP, 2009) in 2001 (taking effect in 2004) because of their persistence, toxicity, and adverse effects on environmental and biological health. These pollutants have a global distribution, with evaporation and precipitation facilitating long-range atmospheric transport, deposition, and bioaccumulation of hazardous chemicals in the environment. However, these chemicals can remain in the environment for decades and interact with various current-use pesticides, including organophosphates, neonicotinoids, and pyrethroids.
Although various studies demonstrate the volatile, toxic nature of POPs, much less research evaluates the impact POPs have on maternal offloading or transfer of contaminates to offspring and respective health consequences. The globe is currently going through the Holocene Extinction, Earth’s 6th mass extinction, with one million species of plants and animals at risk. With the increasing rate of biodiversity loss, advocates say it is essential for government agencies to research how previous and ongoing use of POPs can impact present-day species. Likewise, collaborative, global monitoring of POPs can help leaders identify the effect on vulnerable species of the chemicals’ long-range transport and the most effective unified global strategy. The study notes, “Contaminant studies in cetaceans can provide information about pollutant levels and patterns in a given region.”
The study measured the concentration of POPs in the blubber of female humpback whales across all ages and distinguish contaminants from maternal offloading in offspring. Previous studies typically focused on POP concentrations in males rather than the confounding effects of reproductive status and maternal offloading (transfer of materials) in females. However, contaminant burdens in female whales need better assessment due to the direct transfer of POPs to offspring. Researchers gathered 36 blubber biopsy samples from female humpbacks whale in the Gulf of Maine to determine POP burdens across different ages (i.e., adult, subadult, juvenile, calf). Using gas chromatography/mass spectrometry (GC/MS), researchers identified POPs, including polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethanes (DDTs), chlordane (CHLDs), polybrominated diphenyl ethers (PBDEs), hexachlorocyclohexanes (HCHs).
Overall, the most abundant POPs are PCBs, followed by DDTs and chlordane. PCB levels are above the estimated threshold for adverse health effects. The three aforementioned POPs have a significant difference in abundance between adults and juveniles and adults and subadults, with juveniles and subadults having higher concentrations. However, HCHs are less persistent among humpback whales, with little difference between age classes, except for HCH levels between juveniles and subadults. The researchers emphasize these changes in POP levels across ages “are consistent with maternal offloading and potentially important for evaluating population health and viability.”
Environmental contaminants like pesticides are ubiquitous in the environment, with 90 percent of Americans having at least one pesticide compound in their body. While various POPs on the Stockholm Convention annex lists are no longer manufactured or utilized, many of these chemical compounds remain in soils, water (solid and liquid), and the surrounding air at levels exceeding U.S. Environmental Protection Agency (EPA) standards. Therefore, individuals still encounter various POPs at varying concentrations, adding to the toxic body burden of those chemicals currently in use. Scientific literature demonstrates pesticides’ long history of adverse environmental effects, including wildlife, biodiversity, and human health. The impacts of pesticides on wildlife are extensive and expose animals in urban, suburban, and rural areas to unnecessary risks. Pesticides can affect animals through direct or indirect applications like drift, secondary poisoning, and runoff. Some animals could encounter direct spraying, while others may consume plants or prey contaminated with pesticides. However, the climate crisis adds another level of concern, especially regarding passive pesticide and microbial exposure from snowmelt.
Pesticide contamination has been identified as an issue in the U.S., as results of the United States Geological Survey (USGS) and National Water-Quality Assessment (NAWQA) show that pesticides and their breakdown products are present in all U.S. streams and widespread in groundwater throughout the country. Permafrost and glacial melting will only add to water source contamination as volatile chemicals can enter waterways at the same concentration levels as before ice entrapment, even after several decades. Moreover, several banned chemicals are not soluble in water (e.g., DDT, lindane, chlordane) but bioaccumulate in the fatty tissue of many Arctic species, such as polar bears, seals, whales, and some fatty fish like salmon, herring, and catfish. The level of DDT in Arctic penguins’ blubber is similar to levels found more than 30 years ago when DDT was banned. Like marine invertebrates and birds, many marine mammals demonstrate signs of chemical poisoning, especially from POPs like DDT and PCBs.
This report demonstrates that exposure to chemical contaminants adversely impacts marine mammal health globally. The study notes specific long-term health concerns among the humpback whale population not described in previous reports, including reproductive toxicity, immune dysfunction, and increased susceptibility to disease. Despite the difference in diet (e.g., plankton, lower trophic level fish, etc.) among humpback whales and regional toothed whales, the risk of adverse health effects from POPs exposure remains similar for both cetaceans. However, this study is not the first to highlight instances of chemical contaminant transfer between mother and offspring, specifically among mammals. Beluga whales pass a portion of POPs, like PCBs, to the fetus from blubber storage. Similarly, accumulation in the fatty tissue of bottlenose dolphins in the eastern Atlantic. Studies find dolphins can harbor high concentrations of organochlorine compounds in their brain tissue.
POPs are not the only chemicals that contaminate marine mammal species. A 2020 study finds bottlenose dolphins and pygmy sperm whales along the eastern seaboard contain high triclosan and BPA levels and low levels of atrazine. All three chemicals display endocrine (hormonal) disrupting properties in ranges of animals, including mammals, even at extremally low levels. A 2018 study finds detectable levels of toxic industrial byproducts like “inert” ingredients from pesticide products in bottlenose dolphins inhabiting the Gulf of Mexico. Furthermore, there is growing concern over current-use chemicals like organophosphorus compounds in flame retardants, neonicotinoids, pyrethroids, and other pesticide classes. According to a 2018 study, marine mammals may lack the functioning of a gene that helps terrestrial animals break down certain toxic chemicals. Therefore, whales, manatees, dolphins, and other mammals may display heightened chemical accumulation in fatty tissue and sensitivity to pesticides.
The study concludes, “Due to the confounding effects of maternal offloading, POPs data collected from female marine mammals is less common than that of males, but the adverse health effects, such as immune dysfunction and increased susceptibility to disease, are important to assess the health of a population. In addition, POPs data can be used to develop models that can help determine the potential impacts of these toxic compounds on population growth of cetaceans.”
Chemical contamination is ubiquitous in terrestrial and marine environments. Regarding marine mammals, some indigenous tribes in Arctic regions rely on these very mammals and fish for sustenance, and ingesting these pollutants is inevitable, putting their health at risk. Higher bodily concentrations of chemicals are evident in those who consume contaminated meat with associated health risks, including immune system disorders, increased susceptibility to disease, central nervous system disorders, learning disabilities among children, reproductive issues, and cancer. Therefore, these mammals and other animals can act as sentinel species for chemical contamination, detecting risk to humans by exhibiting signs of environmental threat sooner than humans in the same environment. Unless more is done to address chemical pollution, humans will also continue to see similar declines in general health, fitness, and well-being. Learn more about the hazards pesticides pose to wildlife and what you can do through Beyond Pesticides’ wildlife program page, including mammals.
Replacing pesticides with organic, non-toxic alternatives is crucial for safeguarding public health, particularly in communities vulnerable to pesticide toxicity. A switch from chemical-intensive agriculture to regenerative organic agriculture can significantly reduce the threat of the climate crisis. Organic agriculture eliminates toxic, petroleum-based pesticides and synthetic fertilizer use, building soil health, and sequestering carbon. The Intergovernmental Panel on Climate Change (IPCC) finds that agriculture, forestry, and other land use contribute about 23% of total net anthropogenic emissions of greenhouse gases. However, organic production reduces greenhouse gas emissions and sequesters ambient carbon in the soil. Learn how to sequester more than 100% of current annual CO2 emissions by switching to organic management practices by reading Regenerative Organic Agriculture and Climate Change: A Down-to-Earth Solution to Global Warming. For more information about organic food production, visit Beyond Pesticides’ Keep Organic Strong webpage. Learn more about the adverse health and environmental effects chemical-intensive farming poses for various crops and how eating organic produce reduces pesticide exposure.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source: Environmental Pollution
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