Banned pollutants continue to Impact global Felidae health and habitat

Pollutants can have serious global impacts on wild cat health and habitats. Their destructive impacts on mammal health were first publicized in Rachel Carson’s 1962 book Silent Spring. Carlson’s environmental work exposed the man-made, toxic pesticide DDT (Dichlorodiphenyltrichloroethane) used extensively in agriculture and as a household insecticide up until the 1960s. Her research contributed to the creation of the Environmental Protection Agency (EPA) in 1970.   The EPA proceeded to outlaw Persistent Organic Pollutants (POP), including DDT and PCBs (Polychlorinated Biphenyls) in the 1970s.  A worldwide ban involving these two POPs was finally passed in 2004 through the Stockholm Convention, though DDT is still used for malaria prevention in select areas. Despite POP restrictions in many industrialized countries, high levels of these compounds persist in aquatic and terrestrial environments.

Apex predators, including wild cats, are more likely to have high concentrations of POPs in their bodies because they sit at the top of the food chain. The acute and chronic toxic health effects of POP exposure include allergic reactions, developmental changes, nervous system damage, disruption of the hormone release, cancers, and even death.  

Bobcats are also vulnerable to these pollutants through ingestion and inhalation, because of the way they groom themselves and through their diet. In one of the first studies of PCB exposure in bobcats, a 2013 study analyzed liver tissue samples from roadkill carcasses. Males exhibited higher concentrations of PCBs than females, with the researchers suggesting that lower concentrations of PCBs in females was related to how PCBs are processed in their bodies during lactation. 

Another study measured DDT and PCBs in caracals across urban and rural areas of South Africa. Pollutant exposure was high in all samples. Caracals near human dominated areas exhibited  the highest levels of exposure as they are drawn to these areas by the greater food availability associated with human settlements (e.g. small mammals, human food). The researchers also found that DDT and PCB exposure was associated with elevated white blood cell and platelet counts, thereby increasing chances of disease. This work underscored the widespread exposure of measured toxins across local food webs. 

While these studies demonstrate a measurable impact of PCBS and DDT on wild cats, various measures aimed at decreasing POP concentrations continue to be enacted. Today DDT cannot be legally sold or distributed in the U.S. Moreover, the U.S., Canada, and Mexico have developed a regional action plan to reduce or eliminate emissions of POPs. And the United States along with 71 other countries have signed an agreement (the Rotterdam Convention) where participating nations exchange details of storage, transport, and use of hazardous wastes to optimize informed decisions about their use.  Lastly, the 2023 Stockholm convention reported that mandates aimed at reducing POP levels in humans, wildlife and the environment have been successful.  Stricter regulations pertaining to pollutant use and disposal are crucial, along with continued research to further enhance our understanding of how these chemicals affect wild cats and their ecosystems.  

For more information on POPs, there are multiple resources summarizing the science on the EPA site .

References

Boyles E, and Nielsen CK. 2017. Bioaccumulation of PCBs in a Wild North American Felid. Bulletin of Environmental Contamination and Toxicology. 98:71-75. 

Elias SA. 2024. Reference Module in Earth Systems and Environmental Sciences. Human Habitation of the Cryosphere. Persistent Organic Pollutant. Reference Module in Earth Systems and Environmental Sciences, https://www.sciencedirect.com/science/article/abs/pii/B9780323852425000038.

Leighton, GR., Bishop, J.M., Camarero, PR., Mateo, R., O’Riain, MJ. and Serieys, LE., 2022. Poisoned chalice: use of transformed landscapes increases persistent organic pollutant exposure risk with potential immune effects for an adaptable carnivore. Available at SSRN 3983984.

Lineberry, C. History. How Rachel Carson’s ‘Silent Spring’ Awakened the World to Environmental Peril. 2022. https://www.history.com/news/rachel-carson-silent-spring-impact-environmental-movement.. Accessed November 7, 2024. 

Stockholm Convention on Persistent Organic Pollutants. Outcomes of the effectiveness evaluation of the Stockholm Convention 2023. https://pops.int/TheConvention/Overview/tabid/3351/Default.aspx. Accessed November 7, 2024.

United States Environmental Protection Agency. 2024. DDT - A Brief History and Status. https://www.epa.gov/ingredients-used-pesticide-products/ddt-brief-history-and-status. Accessed November 7, 2024.  

United States Environmental Protection Agency. Learn About Polychlorinated Biphenyls.  2024. https://www.epa.gov/pcbs/learn-about-polychlorinated-biphenyls. Accessed November 7, 2024. 

United States Environmental Protection Agency. Persistent Organic Pollutants: A Global Issue, A Global Response.  2024. Accessed 
November 7, 2024. https://www.epa.gov/international-cooperation/persistent-organic-pollutants-global-issue-global-response#address