What Are Persistent Organic Pollutants and Main POP Sources?

What Are Persistent Organic Pollutants?

• Persistent Organic Pollutants (POPs) are natural or synthetic organic compounds with specific physical and chemical properties that remain undecomposed for very long time when released into the environment due to their resistance to photolytic, chemical and biological degradation.
• These compounds include industrial chemicals such as PCBs (poly-chlorinated biphenyls), harmful pesticides such as DDT and by-products such as dioxins and furans.
• These chemicals are toxic, do not easily degrade in the environment, accumulate in the food chain, and can easily spread and travel long distances from their source through air, water and soil. Persistent Organic Pollutants pose a global environmental and health threat due to their ability to travel long distances worldwide through air currents and to enter the food chain and accumulate in animal and human tissues.
• POPs have high solubility in oil, low solubility in water and semi-volatile properties.
• POPs are generally considered under the main headings of toxicity, persistence, bioaccumulation and long-range transportation.

Stockholm Convention and Türkiye

Prepared by United Nations Environment Programme (UNEP), the Stockholm Convention on Persistent Organic Pollutants (POPs), which aims to protect human health and the environment from the negative effects of chemicals with persistent properties, and to completely eliminate the production, use, trade and release, stocks and waste of these substances by taking measures such as restriction, ban or prevention.

The Convention was signed by our Ministry on May 23, 2001, and was approved by the Turkish Grand National Assembly as Law No. 5871 on April 14, 2009 (Official Gazette: 14.04.2009, No.27200). It was accepted by the Council of Ministers and published on July 30, 2009. (Official Gazette: 30.07.2009, No.27304). The Convention officially entered into force for Türkiye on January 12, 2010.

Within the scope of the Convention, our Ministry has prepared The National Implementation Plan on Persistent Organic Pollutants, which consists of action plans to be implemented on many issues such as development capacity, creation and use of a monitoring system, inventory, containing information regarding the use, export, import, production, distribution and source of chemicals that have persistent organic polluting properties, evaluation of contaminated areas, existing stocks and disposal opportunities, infrastructure, legal regulations, monitoring and research regarding persistent organic polluting chemicals in our country. This National Implementation Plan was submitted to the Convention Secretariat in 2011. This National Implementation Plan was updated and published once on November 30, 2016, and once on June 14, 2022, to include newly added chemicals/chemical groups and update the existing inventories. Work is being carried out to update the national implementation plan within the scope of the new chemicals/chemical groups added to the Convention and to submit it to the Secretariat.

Stockholm Convention’s List of Persistent Organic Pollutants (POPs)

The following 12 Persistent Organic Pollutants (POPs), the so-called “Dirty Dozen”, are the first to be tackled towards global elimination:

Pesticides: Aldrin, Chlordane, DDT, Dieldrin, Endrin, Heptachlor, Hexachlorobenzene, Mirex, Toxaphene.
Industrial Chemicals: Polychlorinated biphenyls (PCBs), Hexachlorobenzene (HCB), Mirex.
Unintentional Releases: Dioxins, Furans, Hexachlorobenzene.
An additional 9 new POPs were identified and listed in the Annexes of the Convention, including:
Pesticides: Chlordecone, Alpha hexachlorocyclohexane, Beta hexachlorocyclohexane, Lindane, Pentachlorobenzene.
Industrial Chemicals: Hexabromobiphenyl, Hexabromodiphenyl ether and heptabromodiphenyl ether, Perfluorooctane sulfonic acid, its salts and perfluorooctane sulfonyl fluoride, Tetrabromodiphenyl ether and pentabromodiphenyl ether.

By-products: Alpha hexachlorocyclohexane, Alpha hexachlorocyclohexane, Beta hexachlorocyclohexane and Pentachlorobenzene.
The POPs listed after these are as follows in chronological order (Annex A-Elimination, Annex B-Restriction, Annex C-emission reduction):

• In 2011, Endosulfan with specific exemptions,
• In 2013, Hexabromocyclododecane (HBCD) with specific exemptions (Annex A),
• In 2015, Hexachlorobutadiene (HCBD), Pentachlorophenol (PCP) and its salts, and Polychlorinated Naphthalenes (PCNs) with specific exemptions (Annex A), and again PCNs to Annex C,
• In 2017, Decabromodiphenyl ether (c-DecaBDE), short-chain chlorinated paraffins (SCCP) with specific exemptions (Annex A), HCBD to Annex C,
• In 2019, Dicofol without exemptions (Annex A), Perfluorooctanoic acid (PFOA), its salts and PFOA related compounds with specific exemptions (Annex A), Perfluoro octane sulfonic acid (PFOS), its salts and Perfluorooctane sulfonyl fluoride (PFOS-F) with specific exemptions (Annex B).
• In 2022, Perfluorohexane sulfonic acid (PFHxS), its salts and PFHxS-related compounds without exemptions (Annex A).
• In 2023, Methoxychlor without exemptions (Annex A), Dechlorane Plus and UV-328 with specific exemptions (Annex A).

As of January 2024, Stockholm Convention contains 30 chemicals and chemical groups in Annex A, two chemical and chemical groups in Annex B, and 7 chemical groups in Annex C.

Table 1. Persistent Organic Pollutants Included in the Stockholm Convention

What are the Main POP Sources?

POPs, which have been used primarily in agriculture since the first half of the last century, have started to be used and produced in various manufacturing industries with developments in technology. In recent years, they have been used in final products as flame retardant and water repellent chemical additives. POPs can be unintentionally released in various industrial areas where the incineration process is involved. The main POP release sources are as follows:

• Waste incineration plants where hazardous waste is burned, including cement kilns;
• Pulp production using elemental chlorine or chlorine-forming chemicals during bleaching;
• Thermal processes in metallurgy;
• Industrial boilers and furnaces using fossil fuels, wood and other biomass fuels;
• Chemicals production (especially chlorophenol and chloranil production);
• Fabric and leather dyeing (using chloranil) and finishing (by alkali extraction);
• Waste oil refining.

How Do POPs Impact Humans and Natural Life?

• Persistent Organic Pollutants enter the human body from the environment and through food, accumulate in adipose tissue and remain in the body throughout human life, causing various health problems, including hormonal disorders, immune system disorders, reproductive disorders and cancer. Persistent Organic Pollutants pass from breast milk to the infant and through the placenta to the fetus, accumulating in the body and showing their impacts at a very early age.
• POPs can be produced for use in various sectors of industry and agriculture, as well as by-products of industrial processes and incineration.

The most significant source of exposure to persistent organic pollutants is food. People take these chemicals into their bodies by consuming meat, fish, poultry, milk and dairy products, particularly those with high fat content.

In addition, people living close to areas where activities such as industrial production and waste incineration are performed are exposed to these chemicals through the water they drink and the air they breathe. Babies and children are much more susceptible to these chemicals and may experience serious health problems in the future by being exposed to these chemicals in the early stages of their lives through breast milk.

Persistent Organic Pollutants interfere with hormonal processes by disrupting the endocrine and immune systems by mimicking chemical carriers naturally found or produced in the body. They cause negative impacts on the reproductive system, especially by adversely affecting hormones. They have also been found to inhibit mental development and cause cancer.