POP(s) – and we are not talking about a music genre

By Juliana Leonel

Edited by Katyanne M. Shoemaker

Persistent organic pollutants, commonly known as POPs, are a group of compounds that are very resistant to degradation. These compounds bioaccumulate, can be transported far from their source through atmospheric and oceanic currents, and can have adverse impacts on living organisms, including humans.

In 2001, representatives from various countries signed an agreement called the Stockholm Convention with the aim of reducing and controlling the production and use of POPs. This treaty went into effect in 2004 with 151 signatory countries. Initially, 12 compounds were classified as POPs, and the participating countries agreed to ban the use of nine of them. Additionally, the use of DDT (we have a post on DDT here) was limited to only malaria control, and the unintentional production of dioxins and furans was to be reduced.

The first 12 POPs were all organochlorine compounds (organic compounds formed by C, H, and Cl), which were divided into three groups according to their use and production. The first group consists of pesticides and herbicides: compounds used to fight agricultural pests such as insects and weeds, which are harmful to the production or storage of grains, fruits, vegetables, wood, etc. The second group includes compounds used in industrial processes, such as polychlorinated biphenyls (PCBs) that were mainly used to cool engines, generators, and transformers. Finally, the third group consists of the dioxins and furans, which are compounds unintentionally produced by some industrial processes. This third group contains  by-products of processes (e.g. metallurgy and steel manufacture) and are not produced for a specific purpose. Over the years, during the Conference of the Parties, another 17 compounds or groups of compounds have been added to the list of POPs.

From left to right: o,p'- DDT, cis-chlordane, PCB 153, perfluorooctane sulfonate, PBDE99

To deal with each of these compounds, they were classified into three annexes. Annex A: compounds that must have their use and production eliminated; Annex B: compounds whose use and production should be restricted and only allowed in specific cases; and Annex C: compounds in which (unintentional) production must be controlled and, where feasible, must be phased out.

Each signatory country is responsible for carrying out inventory of stocks, production, and use of POPs in its territory. In addition, these countries must implement measures to reduce or eliminate the release of both intentionally and unintentionally produced POPs. In some cases, it is possible to request an exemption, to use one of the POPs in exceptional cases for a pre-determined amount of time (Ex: DDT use in case of malaria infestations). Signatory parties are also responsible for conducting systematic monitoring studies to assess whether measures are being effective in reducing the environmental levels of POPs.

Brazil approved the Convention’s text through Legislative Decree No. 204 on May 7th, 2004, and promulgated it via Decree No. 5472, on June 20th, 2005. Implementation of the Convention in Brazil is coordinated by the Ministry of the Environment (MMA) through the Secretary of Water Resources and Environmental Quality.

Although POPs are mainly used on land, their transport to the ocean is quite effective, whether through atmospheric transport, urban drainage, or effluent released directly into coastal regions. In this way POPs have been detected in a wide variety of environments and animals (water, air, soil, sediment, birds, fish, marine mammals, etc.). They have been found at the peak of great mountains and in the depths of the oceans, from the equatorial region to polar regions (see an example here). POPs are a not-so-subtle reminder that environmental contamination has no borders, and it is a problem and responsibility of all the world’s citizens. 


Stockholm Convention Text:


Stockholm Convention - Brazil - MMA


Stockholm Convention Home Page:


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