Results and Confidence

Non-dioxin like PCBs

Good status was achieved in terms of concentrations of non-dioxin like PCB (Sum of 6 CB: 28, 52, 101, 138, 153 and 180, see Good Environmental status table 1) in fish in most evaluated assessment units during the period 2011-2016, as the average concentrations were below the threshold value of 75 µg/kg wet weight (ww) in fish muscle (or 75 ng/g ww) (Results figure 1). At some stations, especially along the coast in the Bothnian Bay (< 3 years data), the Arkona Basin, Gulf of Finland (< 3 years data), Kattegat and in the Quark (< 3 years data), good status was not achieved. The concentrations of PCB showed no trend or were based on too few years of monitoring to do a trend assessment.

The results are based on PCB concentrations in different fish species, but also different matrices, i.e. muscle and liver (Results figure 1). To reduce the variability between different matrices, the threshold value is adapted to differences in lipid content of different matrices.

 

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Results figure 1. Spatial variation of the non-dioxin like PCBs (Sum of 6 PCB) sampling stations in biota (flounder, common dab, herring, cod, European perch, European sprat and eelpout) (left) and status assessment in biota (right). Green colour indicates that the upper 95 % confidence interval for non-dioxin like PCBs concentration is below the threshold value (i.e. good status). Small open circles indicate a status assessment based on only 1-2 years of data (initial data), small filled circles indicate that data is not suitable to assess a trend (treated with initial methodology), large filled circles that no detectable concentration trends can be identified during the whole monitoring period (full data), and the filled arrow indicate that there is a statistically defined upward or downward trend during the monitoring period. Click here to access interactive maps at the HELCOM Map and Data Service: PCBs, dioxin and furan.


Dioxins, furans and dl-PCBs:

Good status was achieved in terms of concentrations of dioxins and furans in fish in most of the evaluated assessment units during the period 2011-2016, as the average concentrations were below the threshold value of 0.0065 TEQ/kg ww (fish muscle, crustaceans or molluscs) (Results figure 2 ).

At some stations in the Bothnian Bay (< 3 years data), the Arkona Basin (< 3 years data), Great Belt and Kattegat (< 3 years data) good status was not achieved. The concentration of dioxins and furans showed no trend or were based on too few years of monitoring to do a trend assessment.

The results are based on dioxin and furan concentrations is acquired from different fish species (Results figure 2) and in some cases different matricies (liver and muscle), which lead to an extra variability in the results due to species/matricies differences.  However, to reduce the variability between different species/matrices, the threshold value is adapted to differences in lipid content of different species/matrices.

 

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Results figure 2. Spatial variation of dioxin and furan sampling stations in biota (European perch, European sprat, flounder, herring and eelpout) (left) and status assessment by assessment unit (right). Green colour indicates that the upper 95 % confidence interval for non-dioxin like PCBs concentration is below the threshold value (i.e. good status). Small open circles indicate a status assessment based on only 1-2 years of data (initial data), small filled circles indicate that data is not suitable to assess a trend (treated with initial methodology), large filled circles that no detectable concentration trends can be identified during the whole monitoring period (full data), and the filled arrow indicate that there is a statistically defined upward or downward trend during the monitoring period. Click here to access interactive maps at the HELCOM Map and Data Service: PCBs, dioxin and furan.

Evaluation of temporal trends

Non dioxin-like PCBs: The data from biota monitoring stations show decreasing or no significant trend for PCBs. Results figure 3 shows examples of different trends at stations in the Baltic Sea. Monitoring data for dioxins and furans are only available in ICES database since 2010, and in all cases these show no significant trend (Results figure 4 shows examples). Furthermore, some dioxin data are not sufficient for trend assessment to be made (i.e. less than 3 years of data) and are therefore only shown as status assessment data and treated with the precautionary 'initial' data approach (see assessment protocol).


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Results figure 3. Temporal trend of the sum of 6 PCBs concentration (ng/g wet weight) in herring and eelpout muscle from the Kattegat and the Bothnian Sea (HQS – threshold level (Human-health Quality Standard), grey colour- confidence level 95% range (see Assessment protocol)).

 

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Results figure 4. Temporal trend of the Sum of dioxins and furans concentration (ng/g wet weight) in herring muscle from the Bothnian Bay and the Eastern Gotland Basin (HQS – threshold level (Human-health Quality Standard), grey colour- confidence level 95% range (see Assessment protocol)).

 

Confidence of the indicator status evaluation

The overall confidence of the assessment is moderate.

The geographical resolution of the current dataset for the coverage of the whole Baltic Sea is high, mainly due to measurements of non-dioxin like PCBs, even so dioxin and furan data were assessed in Denmark, Sweden, Lithuania and Finland so far. No detailed geographical studies to investigate the variability in dioxin and furan concentrations across the whole region have yet been carried out.

It should also be noted that the majority of the monitoring stations are selected as reference stations and potential local problems with PCBs, dioxins and furans may occur in areas not included in the current monitoring programmes.

The confidence of the threshold for the Sum of 6 PCBs is low as this value is derived from the food safety directive and no environmental quality standard is available. Thus, the overall confidence is moderate.