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General information, guides and resources about chemical substances and their risks.

Persistent Organic Pollutants (POPs)

What are they?

Persistent Organic Pollutants (POPs) are chemical substances that have a combination of properties that make them particularly concerning for human health and the environment:

they are persistent, meaning that they resist degradation and can remain in the environment for long periods;
they can bioaccumulate in organisms and increase in concentration along food chains (biomagnification);
they may be highly toxic and cause adverse effects on human health and ecosystems;
some can be transported over long distances and may therefore be found far from the places where they have been produced or used.

Effects associated with certain POPs include disorders of the nervous system, effects on reproduction and development, alterations of the immune system, cancer and endocrine disruption. The specific effects depend on the substance and on the characteristics and duration of exposure.

Due to their properties, POPs are an international concern. The Stockholm Convention on Persistent Organic Pollutants, adopted in 2001, establishes measures to protect human health and the environment through the elimination, restriction or reduction of emissions and releases of these substances.

The European Union implements these obligations mainly through Regulation (EU) 2019/1021 on persistent organic pollutants, which establishes restrictions on the manufacture, placing on the market and use of POPs, measures to reduce their releases, and specific requirements for waste containing or contaminated by them.

What to do?

Due to their persistence and ability to accumulate in living organisms, the precautionary principle should be applied, as there are no established safe levels of exposure, emission or release of POPs that can guarantee that there is no risk to human health and the environment.

The presence of POPs in the workplace should be addressed through a specific risk assessment, taking into account the properties of each substance, the routes of exposure, the concentration and duration of exposure, and the actual working conditions. Given the intrinsic characteristics of POPs, the risk associated with the presence of these substances in the workplace should be considered high.

Prevention should give priority to:

Avoiding the use of POPs whenever possible.
Eliminating or substituting these substances with less hazardous substances or with processes that do not use them, whenever technically possible.
Where elimination or substitution is not possible, avoiding or minimising exposure through collective protective measures, closed systems, containment, local exhaust ventilation and organisational measures.
Using personal protective equipment (PPE) where the above measures are not sufficient.
Preventing emissions, releases and any dispersion of POPs into the environment.
Properly managing waste, materials, equipment and articles containing or contaminated with POPs, in accordance with the applicable legislation.

Prevention should therefore focus on avoiding exposure rather than determining how much exposure can be tolerated. The absence of an occupational exposure limit or compliance with a particular reference value should not be interpreted as a guarantee that exposure is harmless. Where the use of these substances cannot be avoided, exposure should be reduced to the lowest level that is technically possible.

Where a POP is also classified as a carcinogenic, mutagenic or toxic for reproduction (CMR) agent, the specific obligations established by the legislation on protection against these agents shall apply, including giving priority to substitution where technically possible and adopting measures to prevent or reduce exposure where exposure cannot be avoided.

In situations involving pregnancy, recent childbirth or breastfeeding, the risk assessment should specifically consider the possible effects of exposure to POPs. Where a risk exists, the necessary preventive measures should be adopted to protect the health of the worker and, where applicable, reproductive health and the health and development of the fetus or infant, including adapting working conditions or working hours and, where necessary, changing the worker's position.

All unnecessary exposure to POPs should be avoided, with particular attention paid to situations in which there may be increased vulnerability to their effects.

Action guidelines

For the purposes of updating this interface, priority should be given to official documentation and institutional sources:

Classification

The Stockholm Convention establishes three main annexes for substances listed under the Convention:

Annex A – Elimination: Parties shall take measures to eliminate the production and use of substances listed in this annex, subject to any applicable specific exemptions.

Annex B – Restriction: substances are subject to restrictions on production and use, in accordance with the specific provisions established for each substance.

Annex C – Reduction of releases: Parties shall take measures to reduce unintentional releases of substances listed in this annex and, where feasible, ultimately eliminate them.

The Convention also establishes a procedure for assessing new substances. Annexes D, E and F correspond to different stages of this procedure:

Annex D: information relating to the screening criteria for identifying a substance as a potential POP.

Annex E: information on the risk profile, including long-range environmental transport and potential adverse effects.

Annex F: socio-economic information for assessing possible control measures at global level.

Annexes D, E and F should therefore not be presented as categories of POPs equivalent to Annexes A, B and C, but rather as stages in the procedure for assessing new substances.

Since the last RISCTOX update, important substances have been added to the Convention, including:

PFHxS, its salts and PFHxS-related compounds, listed in Annex A in 2022;
methoxychlor, listed in Annex A in 2023;
Dechlorane Plus, listed in Annex A in 2023 with specific exemptions;
UV-328, listed in Annex A in 2023 with specific exemptions.

Stockholm Convention – The New POPs

At COP-12, held in 2025, decisions were also adopted to list the following in Annex A:

chlorpyrifos;
medium-chain chlorinated paraffins (MCCPs);
long-chain perfluorocarboxylic acids, their salts and related compounds, with specific exemptions.

These amendments to the Convention must be distinguished from their incorporation into European Union law. The status and entry into force of individual amendments must therefore be checked separately before presenting them as applicable legal requirements.

Legislation

International

Stockholm Convention on Persistent Organic Pollutants – Convention text and official documents
Decisions of the Conference of the Parties to the Stockholm Convention amending Annexes A, B and C.

Spain ratified the Convention through the Instrument of Ratification published in the Official State Gazette (BOE). Article 7 establishes the obligation to prepare, transmit and periodically update National Implementation Plans. BOE – Instrument of Ratification of the Stockholm Convention

European Union

Regulation (EU) 2019/1021 of the European Parliament and of the Council of 20 June 2019 on persistent organic pollutants (recast).
Subsequent amendments, particularly those updating the Regulation's annexes to include new POPs and establish concentration limits and specific exemptions.

Regulation (EU) 2019/1021 is currently the main EU legislation on POPs and replaced the former Regulation (EC) No 850/2004. The latter should therefore be removed from the interface as current legislation. The current consolidated version available on EUR-Lex is dated 1 January 2026.

EUR-Lex – Regulation (EU) 2019/1021, consolidated version

Among the recent amendments is Commission Delegated Regulation (EU) 2025/843 of 5 May 2025, concerning UV-328, which establishes specific exemptions and progressive limits for UV-328 as an unintentional trace contaminant.

EUR-Lex – Commission Delegated Regulation (EU) 2025/843

Spain

These references should be used where applicable to risk assessment, chemical agents, carcinogenic, mutagenic and reprotoxic agents, pregnancy and breastfeeding, and waste management.

References

Last updated: August 2026.