The GEF Small Grant Programme

POPs Awareness Training Module

Read, learn and test your POPs knowledge

Chapter I: ‘The Dirty Dozen’ and their Characteristics

Persistent Organic Pollutants (POPs) are chemical substances that share common characteristics of persistence, bioaccumulation and the ability to travel long distances far from their sources of origin.1 The Stockholm Convention initially addresses twelve of these known as the “dirty dozen.”

Figure 1.  Pesticide Warehouse, Dominica
Figure 1. Pesticide Warehouse, Dominica
  • POPs are organic chemicals, which means, they are chemical compounds that contain carbon and hydrogen.
  • POPs are persistent, which means, they resist physical, chemical, photolytic, and biological degradation.
  • POPs travel long distances, mainly on air currents, but also by fresh and marine water systems.
  • POPs are semi-volatile which means they evaporate into the air, but they also fall out again onto water bodies and onto the land.

Because of their dispersal patterns, POPs enter and contaminate eco-systems in all corners of the world, both near areas where they are used or produced, but also in areas far distant from where they have ever been used or produced.

Figure 1. Texaphene Tanks, Tanzania
Figure 1. Texaphene Tanks, Tanzania
POPs dissolve easily in fats (lipids), but they do not dissolve easily in water. Therefore, when an organism ingests POPs, it cannot easily excrete them. Since POPs are also resistant to biodegradation, they bioaccumulate in an organism, especially in its fatty tissues, and they bio-magnify as they work their way up the food chain. In aquatic eco-systems, high concentrations of POPs can be found in large fish, fish-eating birds, and mammals that east fish. In terrestrial systems, POPs fall out onto grass and leaves and are biomagnified by large grazing mammals. Humans can accumulate high POPs body burdens by eating contaminated fish, meat and dairy products.2 POPs ignore national and regional boundaries, and they harm human health and eco-systems. POPs impact many species, including whales, Arctic polar bears, Antarctic penguins and biodiversity (and communities) in the isolated Pacific islands.3

There are currently 12 persistent organic pollutants (commonly known as the “Dirty Dozen”) listed in the Stockholm Convention,4 the global treaty designed to protect human health and the environment from POPs:


  • Aldrin, Chlordane, DDT, Dieldrin, Endrin, Heptachlor, Mirex, Toxaphene and Hexachrolobenzene (HCB)5

Industrial Chemicals and Compounds

  • Polychlorinated Biphenyls (PCBs), HCB6

Combustion and Unintentional By-products

  • Dioxins (polychlorinated dibenzodioxins or PCDDs), Furans (polychlorinated dibenzofurans or PCDFs), PCBs and HCB7

Certain POPs substances fall into multiple categories:

The "Dirty Dozen"8
1Pesticide          2Industrial Chemical         3Byproduct
Polychlorinated biphenyls (PCBs)2,3
Polychlorinated dibenzo-p-dioxins (dioxins)3
Polychlorinated dibenzo-p-furans (furans)3

Because of their characteristics, POPs harm human health and eco-systems both in places where they are used and produced, and also in localities far distant from where they are used and produced. Governments of the world adopted the Stockholm Convention on POPs and have begun to implement it with the objective of protecting human health and the environment from these global contaminants.

1United Nations Development Programme, Persistent Organic Pollutants, available at:
2United Nations Environment Programme, Chemicals: Persistent Organic Pollutants, available at:
3Bejarano Gonzalez, Fernando; Citizen’s Guide to the Implementation of the Stockholm Convention; October 2005, available at: pg. 58
4Stockholm Convention; available at:
5Listed in Annex A and B of the Stockholm Convention
6Listed in Annex A of the Stockholm Convention
7Listed in Annex C of the Stockholm Convention (note PCBs and HCB are both intentionally and unintentionally produced).
8U.S. Environmental Protection Agency, Pesticides: Regulating Pesticides, Persistent Organic Pollutants (POPs), available at:

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I Review Quiz:

  1. Due to their characteristics, POPs have caused damage to human populations, organisms and the environment, even in remote regions where they have never been used or produced.
    1.   True
    2.   False
  2. Categories of POPs include:
    1.   Some pesticides; some unintentionally produced byproducts of combustion; and some metals
    2.   PCBs; mercury; and some pesticides
    3.   Some pesticides; some industrial chemicals & compounds; some unintentionally produced byproducts of combustion
    4.   None of the above
  3. POPs have the following common qualities and characteristics?
    1.   Persistence and Bioaccumulation
    2.   Are widely present in fish and wildlife
    3.   Travel long distances on air currents
    4.   All of the above
 Chapter 1: ‘The Dirty Dozen’ and their Characteristics
 Chapter 2: Sources and Uses of POPs
 Chapter 3: Impacts of POPs on Health and Environment
 Chapter 4: Global Institutions and Policies to Reduce and Eliminate POPs
 Chapter 5: Harnessing the Power of NGOs and Communities
 Chapter 6: Case Studies: Local Actions; Global Results
 Chapter 7: Opportunity for National Coordinators and National Steering Committees to Facilitate Results in POPs Focal Area
 Final Quiz: POPs Awareness Self-Test
Quick Reference and Additional Information