WHO reassessment of toxicity ratios of toxic PCDD/F and DL-PCB congeners
No influence of the new toxicity equivalent factors on current EU-legislation
Oct 2024. The publication of the new toxicity equivalent factors (TEF) values for dioxins and DL-PCB by the World Health Organization (WHO) at the beginning of 2024 (WHO(2022)-TEF) will initially have no direct impact on EU food and feed legislation. Food and feed business operators can already build up their own data collection based on the new TEF for their specific products and prepare for future changes in EU legislation. We support you.
Toxicity equivalent factors for dioxins and PCBs
Polychlorinated dibenzodioxins and -furans (PCDD/Fs) and polychlorinated biphenyls (PCBs) are two classes of persistent organic pollutants (POPs) consisting of 210 and 209 different chemical compounds respectively. However, only 17 PCDD/Fs, 12 DL-PCBs and 6 NDL-PCBs are relevant for food and feed legislation in the European Union. The colloquially used term “dioxins” generally refers to these 17 PCDD/Fs and 12 DL-PCBs. These are characterised by a common mode of action of the toxic properties, which vary in their strength.
Fig. 1: Steps in the TEQ calculation
The system of toxic equivalents (TEQ) was developed and introduced to estimate the overall toxic potential of this mixture of substances. Toxicity equivalent factors (TEF) are part of this system. A TEF represents the ratio between the toxicity of a congener of this group and the toxicity of the most toxic congener and is a numerical factor for calculating the TEQ, as shown in figure 1. The TEFs are determined on the basis of scientific studies on the toxic potential of the various dioxins and dioxin-like PCBs and are updated at regular intervals to take account of new findings.
New WHO(2022)-TEFs for dioxins and DL-PCBs
The World Health Organization (WHO) first compiled a list of such toxicity equivalent factors, the WHO-TEFs, in 1998, on the basis of which the EU maximum levels for dioxins and dioxin-like PCBs in food were set in 2001 for the first time. The health assessments in combination with tolerable intake levels, which are carried out by the European Food Safety Authority (EFSA) or corresponding national organisations, are also based on the WHO-TEF. At the beginning of 2024, the WHO published modified factors for some dioxins and dioxin-like PCBs in a review of the WHO-TEFs. An overview of all previously published TEFs including the new WHO(2022)-TEFs is shown in the table below.
Overview of TEF systems for PCDD/Fs and DL-PCBs
| Group | Congener | I-TEF (NATO/CCMS) (1988)[1] | WHO-TEF (1998)[2] | WHO-TEF (2005)[3] | WHO-TEF (2022)[4] |
| Polychlorinated dibenzodioxins and ‑furans (PCDD/Fs) | 2,3,7,8-TetraCDD | 1 | 1 | 1 | 1 |
| 1,2,3,7,8-PentaCDD | 0.5 | 1 | 1 | 0.4 | |
| 1,2,3,4,7,8-HexaCDD | 0.1 | 0.1 | 0.1 | 0.09 | |
| 1,2,3,6,7,8-HexaCDD | 0.1 | 0.1 | 0.1 | 0.07 | |
| 1,2,3,7,8,9-HexaCDD | 0.1 | 0.1 | 0.1 | 0.05 | |
| 1,2,3,4,6,7,8-HeptaCDD | 0.01 | 0.01 | 0.01 | 0.05 | |
| OctaCDD | 0.001 | 0.0001 | 0.0003 | 0.001 | |
| 2,3,7,8-TetraCDF | 0.1 | 0.1 | 0.1 | 0.07 | |
| 1,2,3,7,8-PentaCDF | 0.05 | 0.05 | 0.03 | 0.01 | |
| 2,3,4,7,8-PentaCDF | 0.5 | 0.5 | 0.3 | 0.1 | |
| 1,2,3,4,7,8-HexaCDF | 0.1 | 0.1 | 0.1 | 0.3 | |
| 1,2,3,6,7,8-HexaCDF | 0.1 | 0.1 | 0.1 | 0.09 | |
| 1,2,3,7,8,9-HexaCDF | 0.1 | 0.1 | 0.1 | 0.2 | |
| 2,3,4,6,7,8-HexaCDF | 0.1 | 0.1 | 0.1 | 0.1 | |
| 1,2,3,4,6,7,8-HeptaCDF | 0.01 | 0.01 | 0.01 | 0.02 | |
| 1,2,3,4,7,8,9-HeptaCDF | 0.01 | 0.01 | 0.01 | 0.1 | |
| OctaCDF | 0.001 | 0.0001 | 0.0003 | 0.002 | |
| Dioxinlike PCBs (DL-PCBs) | PCB 77 | --- | 0.0001 | 0.001 | 0.0003 |
| PCB 81 | --- | 0.0001 | 0.0003 | 0.006 | |
| PCB 105 | --- | 0.0001 | 0.00003 | 0.00003 | |
| PCB 114 | --- | 0.0005 | 0.00003 | 0.00003 | |
| PCB 118 | --- | 0.0001 | 0.00003 | 0.00003 | |
| PCB 123 | --- | 0.0001 | 0.00003 | 0.00003 | |
| PCB 126 | --- | 0.1 | 0.1 | 0.05 | |
| PCB 156 | --- | 0.0005 | 0.00003 | 0.00003 | |
| PCB 157 | --- | 0.0005 | 0.00003 | 0.00003 | |
| PCB 167 | --- | 0.00001 | 0.00003 | 0.00003 | |
| PCB 169 | --- | 0.01 | 0.03 | 0.005 |
What will change for food and feed business operators with the publication of the WHO(2022)-TEF?
The publication of the new TEF values for dioxins and DL-PCBs by the WHO at the beginning of 2024 will initially have no direct impact on EU food and feed legislation:
- EU maximum levels and action limits for dioxins and DL-PCBs in food and feed refer to WHO-TEQ data. These are linked to a specific data set of TEFs, currently WHO(2005)-TEF[5,6,7].
- For products to which the maximum levels cannot be applied, a tolerable intake level may be used for classification. EFSA has published such a tolerable weekly intake (TWI) of 2 pg WHO(2005)-TEQ/kg body weight in 2018[8]. This is therefore also linked to a specific data set of TEF factors (here also WHO(2005)-TEF).
Outlook for changes to tolerable intake levels and maximum levels
The European Food Safety Authority (EFSA) is currently working on a new health assessment based on the new TEF. The results are expected to be available in spring 2026[9]. Experts on persistent organic compounds from Eurofins estimate that EFSA will publish a new tolerable intake level based on the WHO(2022)-TEQ data. Subsequently, the European Commission is then expected to adopt new EU maximum levels for food and feed with reference to the WHO(2022)-TEF system. As EFSA already concluded in 2018 that consumption and exposure data from European countries for all age groups indicate that the tolerable intake level derived by EFSA in 2018 is exceeded, a significant reduction of the maximum levels based on current frequency distributions in food and feed is likely in the coming years.
Setting up of a data collection based on the new TEFs
The calculation of toxic equivalents based on the WHO(2022)-TEF is already being carried out additionally within our analytical methods on request, so that food and feed business operators or other interested parties can already build up their own data collection based on the new TEF for their specific products. If the EU maximum levels or action values change in the future, a comparison with the upcoming limit values can be made for these products without any additional analytical effort and without delay. Food and feed companies can therefore prepare themselves already now for future changes in EU legislation without any additional effort.
Analyses of dioxins and PCBs at Eurofins
The Competence Center for Dioxins and Persistent Organic Compounds (POPs) in the Eurofins laboratory network for Food & Feed Testing in Germany - Eurofins GfA Lab Service GmbH - analyses dioxins and PCBs in both food and feed according to EU requirements. In addition to food and feed, biota, water, soil and sediments, materials, chemicals and even human samples (breast milk and blood) can be analysed, too. All analytical methods are accredited according to DIN EN ISO/IEC 17025:2018.
Do you have any questions regarding dioxins and PCBs or their analysis?
Talk to your personal account manager or contact our experts for the analysis of dioxins and PCBs directly.
Relevant sources:
[1] North Atlantic Treaty Organization, Committee on Challenges of Modern Society: Pilot Study On International Information Exchange On Dioxins And Related Compounds: International Toxicity Equivalency Factor (I-TEF) Method of Risk Assessment for Complex Mixtures of Dioxins and Related Compounds. Report Number 176, August 1988.
[2] Van den Berg et al. (1998): Toxic Equivalency Factors (TEFs) for PCBs, PCDDs, PCDFs for Humans and for Wildlife. Environmental Health Perspectives, 106(12), 775
[3] Van den Berg et al. (2006): The 2005 World Health Organization Reevaluation of Human and Mammalian Toxic Equivalency Factors for Dioxins and Dioxin-Like Compounds. Toxicological Sciences, 93 (2), 223–241
[4] DeVito et al. (2024): The 2022 world health organization reevaluation of human and mammalian toxic equivalency factors for polychlorinated dioxins, dibenzofurans and biphenyls. Regulatory Toxicology and Pharmacology, 146 (January 2024), 105525
[5] Commission Regulation (EU) 2023/915 of 25 April 2023 on maximum levels for certain contaminants in food and repealing Regulation (EC) No 1881/2006. OJ L 119, 5.5.2023, p. 103–157. (in the version of 22 July 2024)
[7] Directive 2002/32/EC of the European Parliament and of the Council of 7 May 2002 on undesirable substances in animal feed. OJ L 140, 30.5.2002, p. 10–22. (in the version of 28 Nov 2019)
[8] EFSA (2018): Risk for animal and human health related to the presence of dioxins and dioxin‐like PCBs in feed and food. Scientific Opinion. EFSA Journal 2018;16(11):5333
[9] Federal Ministry for the Environment, Nature Conservation, Nuclear Safety and Consumer Protection (BMUV): New evaluation of toxicity equivalents for dioxins and dioxin-like compounds (Sep 2024)
