8.7 Persistent Organic Pollutants (POPs)

Introduction

What are the Sources of POPs?

• Industrial sources: Many POPs were originally used as industrial chemicals, such as PCBs (polychlorinated biphenyls) which were used as coolants and lubricants in electrical equipment.
• Pesticides: POPs such as DDT (dichlorodiphenyltrichloroethane) and HCB (hexachlorobenzene) were used as pesticides in agriculture and for controlling pests in buildings.
• Incineration and other combustion processes: Dioxins and furans are produced as byproducts of certain industrial processes, such as the burning of certain types of waste.
• Natural sources: Some POPs can also be produced naturally, such as dioxins which are produced by forest fires and volcanic eruptions.
• Long-range transport: POPs can be transported long distances by wind and water currents, leading to their presence in remote areas far from their original source.
• Legacy sources: Even though their production and use have been banned, POPs can still be found in the environment due to their persistence and long-term effects, these chemicals can be found in soil, water and even in human blood and milk due to their accumulation in the food chain.

Health Impacts

Examples

Types of POPs

• DDT (dichlorodiphenyltrichloroethane) is a pesticide that was widely used in the past to control insects on crops and in homes. It was banned in many countries in the 1970s due to its negative impacts on wildlife, particularly birds of prey. DDT is a persistent chemical that can remain in the environment for long periods of time and can accumulate in the fatty tissues of animals, including humans.
• PCBs (polychlorinated biphenyls) are a group of industrial chemicals that were used in a variety of applications, including as coolants and lubricants in electrical equipment. PCBs are highly persistent and can remain in the environment for decades. They have been linked to a variety of health problems, including cancer and developmental disorders.
• Dioxins are a group of chemicals that are produced as byproducts of certain industrial processes, such as the manufacture of pesticides and the burning of certain types of waste. They are highly toxic and can cause a range of health problems, including cancer and developmental disorders.
• Hexachlorobenzene (HCB) is a fungicide and pesticide which has been banned in most countries, but it still present in the environment due to its persistence and long-term effects.
• Chlordane is a pesticide which was used in the past to control termites in homes and buildings. it has been banned in many countries, but it still present in the environment due to its persistence and long-term effects.

Transport of POPs

1. Airborne transport: POPs can be transported through the air by wind and can travel long distances from their source. For example, DDT that was applied in agriculture in one country can be transported by wind and deposited in another country.
2. Waterborne transport: POPs can also be transported through water by rivers, oceans and currents. For example, PCBs that were released into rivers from an industrial facility can be carried downstream and deposited in the ocean.
3. Biomagnification: POPs can accumulate in the fatty tissues of animals and move up the food chain. For example, a bird that eats fish contaminated with POPs will have higher concentrations of POPs in its body than the fish did.
4. Long-range transport: POPs can be transported long distances by wind and water currents, leading to their presence in remote areas far from their original source. For example, POPs released in one continent can be transported by the jet stream and deposited on another continent.
5. Deposition: POPs can also be deposited on land and in water bodies, and can remain in soil and sediment for decades or even centuries.

Impacts of POPs

1. Environmental impacts: POPs can have negative effects on wildlife, including birds, fish, and mammals. For example, DDT can cause thinning of bird eggshells, leading to decreased reproductive success. POPs can also accumulate in the food chain, leading to higher concentrations in animals at the top of the food chain.
2. Human health impacts: POPs can have a range of negative health effects on humans, including cancer, neurological disorders, developmental problems, and reproductive issues. For example, exposure to dioxins can increase the risk of cancer, while exposure to PCBs can cause developmental problems in infants and children.
3. Economic impacts: POPs can have significant economic impacts on industries that rely on natural resources, such as fishing and tourism. For example, the decline of fish populations due to POPs can lead to decreased income for fishermen and related industries.
4. Social impacts: POPs can also have social impacts, such as displacement of communities and loss of livelihoods. For example, if an agricultural community's crops are damaged by POPs, the community may be forced to move or to find new ways to make a living.
5. International impacts: POPs are not bound by national borders and can travel long distances through the air and water, which has lead to their presence in remote areas far from their original source. This makes it difficult to control and manage their impacts, and has led to the need for international cooperation and agreements, such as the Stockholm Convention, to reduce and eventually eliminate their production and use.

What is the Stockholm Convention?

• Annex A includes chemicals that are banned for production and use, such as DDT, hexachlorobenzene, and polychlorinated biphenyls (PCBs).

• Annex B includes chemicals that are restricted for production and use, such as chlordane, dieldrin, and endrin.

• Annex C includes chemicals that are under review for possible inclusion in the future, such as PFOS (perfluorooctanesulfonic acid) and PFOA (perfluorooctanoic acid).

Specific World-Impacts of POPs

• DDT and birds of prey: The pesticide DDT was widely used in the past to control insects on crops and in homes. DDT is a persistent chemical that can remain in the environment for long periods of time and can accumulate in the fatty tissues of animals. DDT was found to cause thinning of bird eggshells, which led to decreased reproductive success and population declines in birds of prey such as the Bald Eagle, Peregrine Falcon, and Osprey in the United States and many other countries.

• Dioxins and Agent Orange: Dioxins are a group of chemicals produced as byproducts of certain industrial processes, such as the manufacture of pesticides. Dioxins were an ingredient of the defoliant Agent Orange, which was used during the Vietnam War. Exposure to Agent Orange has been linked to a range of health problems for veterans, including cancer and developmental disorders.

• PCBs and the Hudson River: PCBs are a group of industrial chemicals that were used in a variety of applications, including as coolants and lubricants in electrical equipment. PCBs were found to have been released into the Hudson River by two General Electric plants in the Hudson Valley. The PCBs have contaminated the river and its fish, leading to health advisories and restrictions on fish consumption.

• Chlordane and health problems: Chlordane is a pesticide which was used in the past to control termites in homes and buildings. It was banned in many countries due to its persistence and negative health effects. However, it can still be found in homes and buildings treated with the pesticide decades ago. Long-term exposure to chlordane can cause neurological effects, liver and kidney damage, and cancer.

• HCB and health effects: Hexachlorobenzene (HCB) is a fungicide and pesticide which has been banned in most countries, but it still present in the environment due to its persistence and long-term effects. Long-term exposure to HCB can cause liver and kidney damage, and cancer.