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Dioxin Levels in Seafood Products

GENERAL - NIFES has examined the levels of dioxins, dioxin-like PCBs and other PCBs in certain fish oils.

In addition, a limited number of filet samples of mackerel, Greenland halibut and Atlantic halibut have been analyzed for dioxins and dioxin-like PCB, brominated flame-retardants and heavy metals. The analyses were done for the Norwegian Food Safety Authority.

The amount of data with respect to dioxins and dioxin-like PCBs in food is very limited in both Norway and the EU. This also applies to data on polybrominated flame-retardants in both seafood and other foods. The reason for this is partly that attention has only recently been drawn to the flame retardants as environmental pollutants.

It is important to expand the data on these substances in seafood in order to facilitate food safety assessments and the establishment of maximum limits for the components in seafood. The analyses reported in this article was previously split into three different projects carried out by the National Institute of Nutrition and Seafood Research (NIFES) for the Norwegian Food Safety Authority.

Focus on certain products and species

Previously, several different marine species and fish oil/oils for human consumption have been analyzed for the content of various undesirable substances. This has been done in order to get an overview of which species needs more attention with respect to seafood safety. These data shows that the content of certain undesirable substances can be high in Atlantic halibut and Greenland halibut compared to EU`s upper limits. The monitoring in 2007 has therefore focused on these species. Mackerel and fish oil/oils for human consumption are also included in this surveillance work because of a need for more data on undesirable substances in these products.

Oils for human consumption

Sixteen different marine oils purchased from various grocery stores in and around Bergen were analyzed for dioxins, dioxin-like PCB and sum PCB7. The concentrations of dioxins and dioxin-like PCBs were low, while the concentration of PCB7 in some of the products was surprisingly high, since these oils were purified. The levels were nevertheless low and do not pose a risk to food safety. There are no upper limits for sum PCB7 in the EU.

Mackerel

50 samples of mackerel were analyzed for dioxins, dioxin-like PCBs and sum PCB7, 25 samples of mackerel were analyzed for brominated flame retardants, and 50 samples were analyzed for metals, i.e. arsenic, cadmium, mercury and lead. The concentrations of these undesirable substances were low compared to EU’s maximum limits, for the substances these limits exist.

Greenland halibut

50 samples of Greenland halibut were analyzed for dioxins, dioxin-like PCBs and sum PCB7. Samples from 10 of these showed a concentration of dioxins and dioxin-like PCBs that exceeded the EU's upper limit of 8 ng TE/kg wet weight. With respect to trade, EU`s upper limit applies to the average levels of a batch. Since the mean value for all 50 Greenland halibut was 5.4 ng TE/kg wet weight, this result does not evoke a ban on distribution.

Ten samples of Greenland halibut were analyzed for brominated flame-retardants. The results showed varying levels, and for polybrominated difenylethers (PBDE) the mean value was 1.8 microgram/kg wet weight. This concentration was somewhat higher than that found in mackerel, but is within the same range as for other marine fish species from the open sea.

Fifty samples of Greenland halibut were analyzed for metals, i.e. arsenic, cadmium, mercury and lead. Five of these exceeded EU`s upper limits for mercury of 0.5 mg/kg wet weight. However, the mean value of mercury was 0.32 mg/kg wet weight for the entire batch and does not evoke a ban on sale.

Several factors affect the levels of undesirable substances in a sample such as specie, geography/location, age, size, diet/level in the food chain and season (i.e. temperature, nutrient access, maturation). More analyses are needed to describe the current situation with respect to undesirable substances through an extensive survey called baseline studies, NIFES is currently working to establish the baseline for Greenland halibut.

Atlantic halibut

Thirty samples (belly and back) of Atlantic halibut (wild) were analyzed for dioxins, dioxin-like PCBs and sum PCB7. Eight of a total of 14 belly samples showed very high levels of dioxins and dioxin-like PCB, with an average of 19 ng TE/kg wet weight, and thereby exceeding EU`s upper limit of 8 ng TE/kg wet weight. Measures to restrict the distribution of belly filets of Atlantic halibut should be considered by the Norwegian Food Safety Authority.

Twenty samples (belly and back) of Atlantic halibut were analyzed for brominated flame-retardants. The levels varied from 0.3-12.3 microgram PBDE/kg wet weight in back filets and from 1.0-17.5 microgram PBDE/kg wet weight in belly filets. Concentrations of PBDE in samples of Atlantic halibut are amongst the highest found in marine fish from the open sea.

Thirty samples of Atlantic halibut were analyzed for metals, i.e. arsenic, cadmium, mercury and lead. Only one of 14 back samples showed levels of mercury that exceeded the EU`s upper limit of 1.0 mg/kg wet weight. The batch average was 0.53 mg/kg and thereby below the EU`s upper limit.

More analyses are required to describe the current levels of undesirable substances in Atlantic halibut. NIFES is working to raise funds for a comprehensive baseline surveys for this specie.

the Fish Site Editor

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