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Daily News Analysis


19th June, 2024 Geography


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Picture Courtesy: https://www.downtoearth.org.in/news/pollution/ddt-levels-have-declined-in-humans-environment-since-2004-but-those-of-other-persistent-organic-pollutants-rising-un-96724

Context: A recent study conducted by the United Nations Environment Programme (UNEP) and sponsored by the Global Environment Facility (GEF) has uncovered important information about the presence of Persistent Organic Pollutants (POPs) in different parts of the world.

Background on DDT and POPs

  • Dichloro-diphenyl-trichloroethane (DDT) along with other Persistent Organic Pollutants (POPs), has been tightly regulated under the Stockholm Convention since 2004.
  • POPs are chemicals that remain in the environment for long periods, accumulate in living organisms, and pose risks to human health and the environment. They are linked to severe health issues such as cancer, liver damage, decreased fertility, and increased risk of asthma and thyroid disease due to their endocrine-disrupting properties.

Dichloro-diphenyl-trichloroethane (DDT)

●It is a colourless, tasteless, and almost odourless chemical compound, originally developed as an insecticide.

●The evolution of DDT resistance and its harm to humans and the environment led many governments to curtail DDT use.

● A worldwide ban on agricultural use was formalized under the Stockholm Convention on Persistent Organic Pollutants, which has been in effect since 2004.

●DDT still has limited use in disease vector control due to its effectiveness in killing mosquitos and reducing malaria infections, but this use is controversial due to environmental and health concerns.

Persistent Organic Pollutants (POPs)

Persistent organic pollutants (POPs) are resistant to environmental degradation, toxic to humans and wildlife, and can travel far from their origin.

●Most are man-made pesticides, solvents, and industrial chemicals, with a significant example being the "dirty dozen" identified by the Stockholm Convention on Persistent Organic Pollutants in 2001.

●POPs bioaccumulate in fatty tissues and are persistent due to their chemical stability, posing long-term risks to health and ecosystems.

●Although international efforts aim to regulate and eliminate these substances, new POPs continue to emerge, raising ongoing concerns about their impact.

Stockholm Convention

●The Stockholm Convention on Persistent Organic Pollutants (POPs) is an international environmental treaty aimed at eliminating or restricting the production and use of POPs.

●It was signed in Stockholm, Sweden, on May 22, 2001, and came into effect on May 17, 2004.

●The treaty was established in 1995 by the United Nations Environment Programme (UNEP) after identifying the 12 worst POPs, known as the "dirty dozen."

●The treaty includes measures to eliminate intentional production and use of POPs, reduce releases of unintentionally produced POPs, and manage POP wastes environmentally. Developed countries are required to provide financial resources for implementation.

United Nations Environment Programme (UNEP)

●The United Nations Environment Programme (UNEP) is a key player in global environmental governance, established in 1972 following the Stockholm Conference.

●It addresses various environmental issues, including climate change, ecosystem management, and green economic development.

●Under the United Nations Development Group, it supports the achievement of the 17 Sustainable Development Goals (SDGs).

●UNEP hosts secretariats of multilateral environmental agreements and co-established the Intergovernmental Panel on Climate Change (IPCC) with the World Meteorological Organization.

●The UNEP's governance structure includes the United Nations Environment Assembly (UNEA), which meets biennially and includes 193 member states.

Global Environment Facility (GEF)

●The Global Environment Facility (GEF) is an international fund that focuses on addressing global environmental issues through financial and technical support.

●The GEF provides grants and blended finance to projects addressing biodiversity, climate change, international waters, land degradation, chemicals and waste management, sustainable forest management, and sustainable cities.

●The GEF's areas of focus include biodiversity conservation, climate change mitigation and adaptation, chemicals and waste management, international water management, land degradation, and sustainable forest management.

●Established in 1991, the GEF became independent post-1992 and has been managed by the World Bank as a Trustee since 1994.

Key Findings of the Study

  • The study monitored 30 POPs across 42 countries, particularly in Africa, Asia, Latin America, the Caribbean, and the Pacific Islands, where data on POPs had been limited.
  • Sampling and Data Collection: Between 2016 and 2019, over 900 samples were collected from air, water, human milk, soil, beef, milk, milk powder, butter, mutton, pork, chicken, eggs, fish and shellfish, oil, and other items. This extensive sampling generated more than 50,000 data points on the presence of POPs.
  • Decline of DDT: The levels of 12 POPs, including DDT, have declined globally since the regulatory actions of the Stockholm Convention in 2004. Notably, DDT levels in human milk have decreased by over 70% on a global average. However, DDT remains the most prevalent POP in human milk, particularly in regions where it was heavily used in the past.

Ongoing Challenges with POPs

  • Despite the decline of DDT, other POPs continue to persist in the environment. For instance, chemicals like dieldrin and polychlorinated biphenyls (PCBs), which have been regulated for a long time, are still found at elevated levels in the air in Africa, the Caribbean, and Latin America.
  • Emerging POPs: The report highlights the worrying trend of chemical replacements for banned POPs being detected at high levels. Specifically, per- and polyfluoroalkyl substances (PFAS), including PFOS, PFOA, and PFHxS, were found in human milk and drinking water in remote islands, exceeding European Union and United States standards.
  • Monitoring Difficulties: Newly listed POPs are increasingly difficult to monitor, even for the world's top laboratories. While there has been improvement in data collection and participation of more laboratories in low-income countries in UNEP’s global interlaboratory assessments, the quality of POP analysis needs to continue improving.

Implications and Recommendations

The continued presence and detection of POPs, including their replacements, underline the importance of sustained and improved monitoring efforts. The study’s findings stress the necessity of:

  • Enhanced Monitoring: Continuous monitoring of POPs in the environment and human bodies is crucial, especially in low- and middle-income countries, to support assessments of contamination, emissions, and exposure to these hazardous chemicals.
  • Avoiding Regrettable Substitutions: Governments and industries must avoid the cycle of replacing one harmful POP with another equally hazardous chemical. This calls for a focus on sustainable industrial product design and consumer behaviour to prevent new toxic threats.
  • Informed Decision-Making: Reliable and comprehensive data on POPs is essential for informed decision-making and effective regulatory actions to protect human health and the environment.

Persistent Organic Pollutants (POPs)

  • Persistent Organic Pollutants (POPs) are chemicals characterised by their persistence in the environment, ability to bioaccumulate in living organisms, and adverse effects on human health and the environment.

Characteristics of Persistent Organic Pollutants (POPs)

  • Persistence: POPs are chemicals that resist degradation through chemical, biological, and photolytic processes in the environment. This allows them to remain in the environment for long periods, potentially spanning decades or even centuries.
  • Bioaccumulation: These chemicals accumulate in the fatty tissues of living organisms through the food chain. Organisms at higher trophic levels, such as predators, can accumulate higher concentrations of POPs than those lower in the food chain, leading to potential biomagnification.
  • Adverse Effects: POPs are associated with a range of adverse effects on human health and the environment, including reproductive and developmental disorders, neurological impacts, immune system suppression, and cancer. They can also harm ecosystems by affecting wildlife populations and biodiversity

Examples of Persistent Organic Pollutants (POPs)

  • DDT (Dichlorodiphenyltrichloroethane): A pesticide historically used to control insects like mosquitoes, known for its persistence and impact on wildlife and human health.
  • PCBs (Polychlorinated Biphenyls): Industrial chemicals used in electrical equipment, coatings, and other applications. Banned in many countries due to their toxicity and persistence.
  • Dioxins and Furans: Produced as by-products of industrial processes involving chlorine, such as waste incineration and chemical manufacturing. Highly toxic and persistent in the environment.

Sources of Persistent Organic Pollutants (POPs)

  • Industrial Processes: Production and use of chemicals like PCBs, dioxins, and furans in industrial activities. Waste incineration and metal smelting are significant sources.
  • Agricultural Activities: Pesticides like DDT and other organochlorines used in agriculture. These chemicals can persist in soils and water bodies, affecting ecosystems.
  • Consumer Products: Some POPs are used in consumer goods such as flame retardants (e.g., PBDEs) and chemicals in plastics (e.g., phthalates). These can leach into the environment during use and disposal.

Pathways of POPs

  • Air: POPs can be transported over long distances through the atmosphere. They are released into the air primarily through industrial processes, waste incineration, and volatilization from contaminated surfaces. Once airborne, they can travel globally via atmospheric currents and settle back to the Earth's surface through precipitation or atmospheric deposition.
  • Water: POPs are discharged into water bodies such as rivers, lakes, and oceans through industrial and agricultural runoff, as well as from atmospheric deposition. They can accumulate in sediments and persist in aquatic environments, where they bioaccumulate in aquatic organisms such as fish and shellfish. This bioaccumulation magnifies concentrations of POPs up the food chain, posing risks to higher trophic level species and potentially to humans who consume contaminated seafood.
  • Soil: POPs can also accumulate in soil through atmospheric deposition, agricultural practices, and industrial activities. Once in the soil, they can persist for long periods and may be taken up by plants or ingested by soil-dwelling organisms. This pathway can lead to the contamination of terrestrial ecosystems and exposure of wildlife and humans through the consumption of contaminated food crops or direct contact.

Environmental Impact of POPs

  • Bioaccumulation: POPs accumulate in the fatty tissues of organisms, with concentrations increasing up the food chain. Predators at the top of the food web, such as large fish, marine mammals, and birds of prey, can accumulate high levels of POPs, leading to potential toxic effects and reproductive disorders.
  • Ecological Effects: POPs can disrupt ecosystems by affecting the reproductive success, behaviour, and survival of wildlife. They contribute to biodiversity loss and can impair the functioning of ecosystems, reducing their resilience to other environmental stressors.
  • Long-range Transport: Due to their persistence and volatility, POPs can travel long distances from their source of emission. They are transported globally through atmospheric and oceanic currents, leading to the contamination of remote regions far from their point of origin. This global distribution makes POPs a concern for regions that may not produce or use these chemicals but are still affected by their environmental and health impacts.

Health Effects of POPs

  • Human Exposure: People can be exposed to POPs through inhalation of contaminated air, ingestion of contaminated food and water, and dermal contact with contaminated surfaces. Occupational exposure can occur during the production and application of POPs.
  • Health Risks: POPs are associated with a range of serious health effects, including cancer (such as breast cancer and prostate cancer), reproductive disorders (such as reduced fertility and birth defects), developmental effects (such as neurodevelopmental disorders in children), and immune suppression. Some POPs are also endocrine disruptors, affecting hormonal balance in the body.
  • Vulnerable Populations: Certain groups are particularly vulnerable to the health effects of POPs, including children, whose developing bodies may be more susceptible to toxic effects, and pregnant women, whose exposure can impact fetal development. Indigenous communities and subsistence populations relying on traditional diets may also face higher exposure risks due to their reliance on locally caught fish and wildlife.

Management and Mitigation

  • Clean-up Efforts: Remediation activities focus on cleaning up contaminated sites where POPs have accumulated. Techniques include soil and groundwater remediation, waste disposal, and environmental restoration to reduce environmental risks and restore ecosystem health.
  • Education and Awareness: Public outreach and education programs raise awareness about the risks of POPs and promote safer practices. Targeted education efforts aim to inform communities, industries, and policymakers about the importance of reducing POPs and complying with regulatory requirements.
  • Research: Ongoing research advances scientific understanding of POPs, including their behaviour in the environment, mechanisms of toxicity, and long-term effects. Research findings contribute to evidence-based decision-making, support policy development, and inform strategies for managing POPs more effectively.


  • Persistent Organic Pollutants (POPs) continue to pose significant challenges to global environmental and human health. Through international agreements like the Stockholm Convention, stringent national regulations, adoption of best practices, systematic monitoring, robust risk assessment, proactive management efforts, and continuous research, progress is being made in mitigating the impacts of POPs. The collective efforts of governments, industries, researchers, and communities are essential in achieving sustainable reductions in POPs and safeguarding ecosystems and public health for future generations.


Down to Earth




Q. The term "tragedy of the commons" refers to a situation in which individuals act selfishly and diminish a shared resource. Air and water pollution frequently cross national borders. How can international cooperation be improved to solve transboundary pollution concerns while accounting for the complexities of economic interests, political boundaries, and varying environmental regulations?