Understanding POPs (Persistent Organic Pollutants)

What are POPs and why are they a concern?

POPs are organic compounds that resist degradation through chemical, biological, and photolytic processes.  

This stability means they don’t break down easily in nature. Instead, they accumulate in soil, sediments, and the fatty tissues of living organisms, including animals and humans, causing adverse health effects. They can remain in the environment for years, if not decades, through bioaccumulation. 

A process known as biomagnification means that concentrations increase up the food chain, making top predators, including humans, particularly vulnerable to their impacts. What’s more, POPs chemicals can travel thousands of kilometers with transboundary movements, via air and ocean currents, contaminating even remote regions such as the Arctic, affecting delicate ecosystems.  

Examples of POPs

POPs include a variety of industrial chemicals, pesticides, and unintentional byproducts of industrial processes. POPs were used in the agricultural industry during the 1940s for pest control and also found in plastic and rubber products, and flame retardants.  

Some of the best-known examples are: 

• DDT: A widely used insecticide banned in many countries but still persistent in soils and sediments decades later. 

• Polychlorinated biphenyls (PCBs): Industrial chemicals used in electrical equipment and other applications. PCBs are highly toxic and remain widespread in the environment. 

• Dioxins and Furans: Unintentional byproducts of combustion and certain industrial processes. Extremely toxic even in minute quantities. 

• Hexachlorobenzene (HCB): Used as a pesticide and in chemical manufacturing. 

• Aldrin, Dieldrin, Endrin: Pesticides with severe environmental and health impacts. 

Health and environmental impacts of POPs

POPs are persistent and highly toxic. The impacts they have on human health can be serious. Many POPs are known, or suspected carcinogens and POPs can cause endocrine disruption, interfering with hormonal systems, leading to reproductive, developmental, and immune problems. They can also cause neurological effects as exposure can affect the development of the brain and nervous system, especially in children. Despite these known impacts, there is still much that is not yet known about the mechanisms involved in adverse health impacts from POPs. 

For wildlife, POPs are equally devastating. Because of biomagnification, top predators such as birds of prey, marine mammals, and large fish can have dangerously high concentrations in their bodies. Effects include: Reduced fertility, birth defects, immune suppression, increased mortality rates and ecosystems in the most remote parts of the world are not safe as wildlife is exposed through long-range atmospheric transport. 

Global response to POPs: The Stockholm Convention

Recognizing the global threat posed by POPs, the international community adopted the Stockholm Convention on Persistent Organic Pollutants in 2001. This landmark treaty aims to eliminate or restrict the production and use of POPs worldwide. While many are banned, some uses may be allowed under strict controls (for example, DDT for malaria control in specific situations). There are also measures to minimize or eliminate unintentional releases. For example, dioxins and furans are byproducts of many industrial processes, and completely eliminating their release requires ongoing improvements in technology and regulation. 

The Convention initially targeted 12 POPs (the “Dirty Dozen”) but has since expanded to include additional substances, recognizing the evolving threat from new chemicals with POP-like characteristics. A key part of tackling POPs is through heightened awareness and monitoring them in the environment. There are significant challenges that need tackling such as legacy contamination, where POPs persist in soils, sediments, and living organisms and some countries have stockpiles of banned POPs that require safe disposal.  

Managing POPs

Addressing POPs requires robust monitoring to track levels in air, water, soil, and living organisms. Many countries participate in regional and global monitoring programs that help identify trends, evaluate the effectiveness of controls, and guide policy decisions. 

Scientific research is also critical to provide insights into how POPs move through and transform in the environment and to determine their toxicological effects on humans and wildlife. There needs to be research on safer alternatives and technologies to reduce both emissions and exposure. 

Reducing the threat and adverse effects of POPs requires coordinated action at multiple levels from government, industry, and individuals. 

Governments can enforce bans and restrictions, manage stockpiles safely, invest in cleaner technologies, and support international treaties. In parallel, industry can develop and adopt safer alternatives, improve production processes to minimize unintentional POPs, and manage waste responsibly. 

Individuals can help simply by reducing the demand for products that contribute to POP emissions (e.g. advocating for cleaner waste disposal practices), and by staying informed about environmental issues, supporting the policies and organizations working to reduce pollution.