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Sources of Persistent Organic Pollutants

According to the European Commission, persistent organic pollutants (POPs) are chemical substances that bioaccumulate in the food web, and pose a risk to human health and the environment. POPs consist of pesticides, such as dichlor-diphenyl-trichloroethane (DDT), industrial chemicals and unintentional byproducts of industrial processes. POPs pose a threat to people and ecosystems across the world due to long-range transport of POPs to regions where they have never been used. The main sources of POPs can be grouped into five categories.

Thermal Processes
- According to the World Bank, practices involving elevated temperatures and combustion processes can be important sources of POPs. These include practices such as primary copper smelting, iron ore sintering for blast furnaces, and secondary scrap metal processing. The materials used, effectiveness of combustion and pollution control are critical to the amount of POPs released. For instance, tire burning occurs without controls on air pollution, thus the levels of POPs released are particularly high.
Recycling Processes
- Some recycling processes, in addition to those involving thermal processes, can be a source of POPs. Processes such as solvent and waste oil recovery, and metal, paper and plastic recycling can all release POPs, such as polychlorinated dibenzofurans and polychlorinated dibenzo-p-dioxins, as explained by the World Bank.
Waste Disposal
- Non-thermal waste disposal can also be a source of POPs. Landfills can release polychlorinated biphenyls and hexachlorobenzene, both of which are toxic and pose a serious threat to the environment due to their ability to bioaccumulate. For instance, the UK Environmental Agency explains how hexachlorobenzene can build up in animals and lead to effects on reproduction and birth defects. Moreover, hexachlorobenzene can react with other air pollutants to form ground-level ozone, which can have potential effects on human health.
Product Application
- Industrial bleaching and dying of textiles and leather can release POPs. More commonly, pesticide/herbicide application can lead to bioaccumulation of POPs within the food chain, causing adverse impacts on animal and human health. For instance, the U.S. EPA explains how the pesticide DDT was heavily used on agricultural crops worldwide, in addition to being used to protect soldiers against harmful insect-borne diseases, such as malaria, during World War II. The heavy use of this pesticide led to widespread environmental contamination and the accumulation of DDT in humans and wildlife. For example, according to the U.S. EPA, high levels of DDT in certain birds of prey caused their eggshells to thin to the extent that they could not produce live offspring.
Manufacturing Processes
- Manufacturing, such as textile manufacturing, of chemicals and products that use materials containing POPs can be a source of POPs. According to the World Bank, release of POPs through these types of activities occurs mainly through discharges of liquids and sludges.

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