PCBs and Dioxins in Fish Oil

PCBs and dioxins — these terms cause unease. They represent decades of industrial pollution, persistent toxins that accumulate in the environment and in the fatty tissue of living organisms. No wonder that many people taking Omega-3 capsules ask themselves: are these contaminants also in my fish oil? The short answer is: in raw, unprocessed fish fat yes — but in well-distilled quality fish oil in amounts well below legal limits and toxicologically relevant thresholds. This article explains what PCBs and dioxins are, how they get into fish oil, what EU limits apply and how you as a consumer can ensure you are buying a clean product.

What Are PCBs and Dioxins?

PCB stands for polychlorinated biphenyls — a group of 209 different chlorinated aromatic compounds that were industrially produced and used in large quantities between the 1930s and 1970s. They were considered chemically stable, flame-resistant and electrically insulating — ideal properties for use in transformers, capacitors, hydraulic oils, paints and varnishes. The problem: precisely this stability makes them persistent organic pollutants (POPs). PCBs barely break down in the environment, they accumulate in soils, sediments and especially in fatty tissue.

PCB production was banned in most Western countries in the 1970s and 1980s — internationally through the Stockholm Convention of 2001. Nevertheless, PCBs are still detectable globally in the environment: in marine sediments, in the air above industrial regions, in the fatty tissue of marine mammals, birds and fish.

Dioxins (polychlorinated dibenzo-p-dioxins, PCDD) and furans (polychlorinated dibenzofurans, PCDF) are not deliberately produced chemicals but unwanted by-products: they form during the combustion of chlorine-containing compounds (waste incineration, wildfires), in the manufacture of chlorinated pesticides, in metallurgical processes and in the bleaching of paper with chlorine. Dioxins are also persistent and fat-soluble — and also regulated by the Stockholm Convention.

Certain PCB compounds behave biochemically similarly to dioxins and are classified as "dioxin-like PCBs" (dl-PCBs). For regulatory purposes they are assessed together. Other PCBs are referred to as "non-dioxin-like indicator PCBs" (ndl-PCBs) and measured separately. This distinction is important for understanding EU limits.

How Do PCBs Enter Marine Fish?

The path of PCBs from industrial sources into fish oil on your table follows a clear food chain logic. Atmospheric inputs, industrial effluents and historic landfills have led to PCBs accumulating in marine sediments — particularly in coastal waters, the Baltic Sea and the North Sea. Benthic organisms (living on the sea floor) absorb PCBs from the sediments. Zooplankton and small crustaceans absorb PCBs from the water and from suspended particles.

From there, biomagnification sets in: small fish eat plankton and accumulate PCBs in their fatty tissue. Larger fish eat small fish and concentrate the PCBs further. At the top of the food chain — in marine mammals such as harbour porpoises and seals — the highest PCB concentrations are found, sometimes 10,000 times higher than in seawater.

Since PCBs are fat-soluble, they transfer into the oil when fish fat is pressed or extracted. Raw fish oil, directly after extraction, therefore contains varying amounts of PCBs and dioxins depending on the source fish and geographic region. This is where processing comes in: molecular distillation removes these substances before the oil is filled into capsules.

PCBs and Dioxins in Fish Oil: What Is the Risk?

Raw, unrefined fish oil can contain relevant amounts of PCBs depending on its origin. A 2019 study, published in Food and Chemical Toxicology, examined various commercial fish oils before and after distillation. Crude fish oils from Atlantic herring contained on average 3–8 pg dl-PCB/g fat — values that depending on the product were close to or above the EU limit. After distillation, values fell to below 0.5 pg/g, well below the limit.

Distilled quality fish oil typically shows the following values in practice: dioxins + dl-PCBs below 1 pg WHO-TEQ/g fat (EU limit: 10 pg), indicator PCBs below 20 ng/g fat (EU limit: 200 ng/g). This corresponds to a reduction of the limit by a factor of five to ten.

For comparison: raw farmed salmon contains according to EFSA studies typically 2–5 pg dl-PCB/g fat. Fresh Baltic herring can reach values of up to 8 pg/g — close to the EU limit of 10 pg/g that applies to fatty sea fish. High-quality fish oil capsules are in this respect actually safer than direct fish consumption when it comes to PCBs.

EU Limits for PCBs and Dioxins in Fish Oil: The Numbers in Detail

Contaminant group	Parameter	EU maximum level (fish oil supplement)	Typical value quality fish oil
Dioxins	PCDD/PCDF (pg WHO-PCDD/F-TEQ/g fat)	≤ 1.75 pg/g	< 0.2 pg/g
Dioxins + dl-PCBs	PCDD/F + dl-PCB (pg WHO-PCDD/F-PCB-TEQ/g fat)	≤ 10 pg/g	< 1 pg/g
Indicator PCBs (ndl-PCBs)	Sum PCB28+52+101+138+153+180 (ng/g fat)	≤ 200 ng/g	< 20 ng/g

The unit "pg WHO-TEQ/g fat" (picograms toxic equivalents per gram of fat) is the internationally standardised unit of measurement for dioxins and dioxin-like compounds. The toxic equivalent takes into account that different dioxin and PCB compounds have different toxicity — the most toxic compound (2,3,7,8-TCDD) has the TEQ factor 1.0, less toxic compounds correspondingly lower factors.

Distillation and Molecular Distillation as a Solution

Molecular distillation is for fish oil the equivalent of water treatment in drinking water supply: it reliably removes what does not belong in the end product. The process uses high vacuum (below 0.001 mbar) at moderate temperatures (80–120°C). Under these conditions, the lighter, more volatile Omega-3 fatty acids EPA and DHA evaporate preferentially, while heavy, non-polar PCB molecules and dioxins remain behind or are collected in a separate fraction.

The decisive advantage over conventional vacuum distillation is the short residence time of the vapour on the condenser — hence the name "short-path distillation". The sensitive Omega-3 fatty acids are not damaged by prolonged heat exposure, while the separation of contaminants is highly efficient. A leading manufacturer can achieve PCB contents of below 0.5 pg TEQ/g fat after two distillation passes — corresponding to 2% of the EU limit.

Molecular distillation removes not only PCBs and dioxins but simultaneously also heavy metals, pesticides, other halogenated compounds and oxidised fatty acids. Our article on heavy metals in fish oil provides further details on this purification process and its effects on mercury, lead and arsenic.

Which Fish Species Are Most Contaminated with PCBs?

Not all fish are equally contaminated — and the differences are considerable. PCB contamination depends on three main factors: the region of origin (waters closer to industry are more contaminated), position in the food chain (higher position means more bioaccumulation) and the fat content of the fish (more fat means more fat-soluble contaminants).

Baltic herring is historically particularly heavily contaminated, because the Baltic Sea is a semi-enclosed sea with a large industrial catchment area. EFSA studies show that Baltic herring regularly reaches values of 5–10 pg dl-PCB/g fat — close to the EU limit of 10 pg/g. Atlantic herring from less industrialised waters is typically well below this.

Farmed salmon is frequently discussed in public as a PCB issue. Studies do indeed show that farmed salmon from European aquaculture farms contains 2–6 pg dl-PCB/g fat depending on feed composition — while wild salmon from the Pacific typically stays below 1 pg/g. Since farmed salmon is fed fishmeal that can itself contain PCBs, the contamination accumulates.

Anchovies and sardines from the south-east Pacific (Peru, Chile) — the most common raw material source for high-quality fish oil — have on the other hand very low PCB contents: typically below 0.5 pg dl-PCB/g fat, i.e. one-twentieth of the EU limit. This is due to the low industrial density in the South Pacific and the short lifespan of these small fish.

EU Limits and What They Mean for Consumers

The EU limits for PCBs and dioxins in fish oil food supplements (laid down in Regulation 2023/915, which updates the earlier Regulation 1259/2011) should not be understood as an "everything below this is harmless" threshold. They designate the maximum levels that the EU considers acceptable on the basis of EFSA's scientific risk assessment. The actual health effect depends on total exposure — that is, on everything you eat daily, not just the fish oil capsules.

The World Health Organisation (WHO) has established a tolerable monthly intake (PTMI) of 70 pg WHO-TEQ/kg body weight for dioxins and dl-PCBs. A 70-kg person may therefore ingest 4,900 pg TEQ per month. Two fish oil capsules of 1 g each with a dl-PCB content of 1 pg/g would deliver 2 pg TEQ daily — 60 pg per month, i.e. roughly 1.2% of the tolerable amount. That is not zero, but it is negligibly small.

For comparison: someone who eats 150 g of farmed salmon with 3 pg dl-PCB/g fat (fat content approx. 13%) once a week ingests approximately 600 pg TEQ — ten times more than through daily fish oil capsules. High-quality fish oil capsules are therefore a significantly more controlled and measurably safer method of obtaining EPA and DHA than regular consumption of heavily contaminated fatty fish.

How to Recognise PCB-Tested Fish Oil

There are three reliable ways to ensure that a fish oil product has actually been tested for PCBs and dioxins and shows clean values.

The first way is the Certificate of Analysis (COA). A reputable manufacturer makes available for every production batch a COA from an independent, accredited laboratory. The COA should explicitly state the values for dl-PCBs (in pg WHO-TEQ/g fat), ndl-PCBs (indicator PCBs in ng/g fat) and dioxins. If these details are absent, that is a warning sign. The COA should be publicly accessible on the manufacturer's website or made available on simple request.

The second way is IFOS certification. The International Fish Oil Standards Programme of the University of Guelph (Canada) analyses fish oil products for heavy metals, PCBs, dioxins, oxidation and EPA+DHA content and publishes the results publicly on the IFOS website. Only products meeting all limits receive the IFOS seal. It is the strictest and most transparent certification system for fish oil worldwide. More about IFOS and other certifications in our certification article.

The third way is raw material transparency. Manufacturers who state on their packaging or website that their oil comes from anchovies, sardines or herring from the Pacific and has been double-molecularly distilled generally offer the greatest transparency. Products without details about raw materials or processing should always be viewed critically.

Frequently Asked Questions

Sources and Further Information

• EU Regulation 2023/915 — Maximum levels of contaminants in foodstuffs (EUR-Lex)
• EFSA — Dioxins and PCBs (overview and scientific opinions)
• BfR — Questions and answers on PCBs in food