What is persistent organic pollutants?

Environmental Health: What is persistent organic pollutants? 

■  Definition and characteristics of persistent organic pollutants

Persistent organic pollutants, also known as POPs, are substances that accumulate in the body and disrupt the human endocrine system and damage the immune system. Toxicity, persistence, and bioaccumulation and long-range transport. Most chemicals classified as POPs are highly fat-soluble and tend to accumulate in fatty tissues, and are found in particularly high concentrations in animals and humans at the top of the food chain. The half-life of POPs in the human body varies depending on the individual chemical, but most range from several years to several decades.

• Toxicity: Long-term exposure to POPs through different pathways can lead to both immediate and long-lasting harmful effects. This includes causing cancer, damaging the central nervous system, disrupting reproductive functions, and weakening the immune system. They also act as endocrine disruptors, disturbing the hormonal balance in exposed individuals and potentially affecting future generations.
• Persistence: While 99.9% of chemical substances break down and transform into other forms during transport, POPs are exceptionally stable compounds that resist decomposition and persist in the environment for extended periods.
• Bioaccumulation: Once inside the body, POPs are not easily expelled and build up in fatty tissues due to their tendency to dissolve in fats (lipophilicity). This leads to higher concentrations of these pollutants as they move up the food chain, with humans at the top facing the greatest risk from exposure to elevated levels.
• Long range transport: Characterized by the ability to travel long distances through water or air, and substances are found even in areas far from their source. In other words, POPs are a global problem, not a national or regional problem.

  ■   Specific characteristics of POPs outlined in the Stockholm Convention

	Key Features
Toxicity	If it is a substance that has harmful effects on the human body or living organisms, such as causing cancer or disrupting the endocrine system.
Persistence	If the half-life of the chemical is more than 2 months in water, 6 months or more in soil or sediment, or other substances are judged to have high persistence.
Bioaccumulation	Decomposition occurs at an extremely slow rate, leading to a biological concentration coefficient exceeding 5,000 and an octanol-water partition coefficient (Log Kow) value of 5 or higher. In other instances where biological concentration is deemed to be high.
Long range transport	Cases with an atmospheric half-life of more than 2 days and long-distance mobility of hundreds or thousands of kilometers through wind, ocean currents, migratory birds, etc.

 

■   Stockholm Convention on Persistent Organic Pollutants

The Stockholm Convention on Persistent Organic Pollutants is an international agreement that prohibits or restricts the manufacture, use, export, and import of specific substances aimed at reducing persistent organic pollutants (POPs). It was adopted by the United Nations Environment Programme (UNEP) in May 2001 and came into force on May 17, 2004.

 

■    Types of persistent organic pollutants

 

• Annex A (Elimination)

• Annex B (Restriction)

• Annex C (Unintentional production)

 

■    References

• Curtis D. Klaassen. Casarett and Doull’s Toxicology. McGraw Hill / Medical; 9th edition (2018)
• Stockholm Convention - Home page – POPs: https://chm.pops.int/ Access date: 2024-03-03