​​​​​​​​Results and confidence

Overall the status of polybrominated diphenyl ethers (PBDEs) fail the threshold value (Results figure 1). Data is available across a wide spatial area and shows that the concentrations of PBDEs are above the threshold value in biota throughout the Baltic Sea..


Results figure 1.jpg

Results figure 1. Aggregated mean concentrations in biota per scale 4 HELCOM assessment unit. The bars represent the upper 95% confidence interval. The threshold value is exceeded (failed) in all areas. 


PBDE_trend_biota.pngPBDE_status_biota.png

Results figure 2. PBDE biota measurements per station in the Baltic Sea (right) and resulting status assessment (left). Red colour indicates that the upper 95 % confidence interval for PBDE concentrations are above the threshold value. Small open circles indicate a status assessment based on only 1-2 years of data, small filled circles indicate that there is not enough data to assess a statistical trend, large filled symbols indicate statistical trends assigned with circles indicating no detectable trend in concentration during the whole monitoring period and the filled arrows indicating significant upward or downward trend in concentration during the monitoring period. Click here to access interactive maps at the HELCOM Map and Data Service: PBDEs.


The threshold value of 0.0085 µg/kg ww defined by the Environmental Quality Standard (EQS) is exceeded everywhere, but there are regional/local differences in concentration.

Mean values for the monitoring stations range from 0.03 to 0.82 ng/g ww in fish muscle (0.098 to 3 ng/g ww per scale 4 HELCOM assessment unit). However, the PBDE levels in a single, widespread species, e.g. herring seems to vary less throughout the Baltic Sea than for other substances such as for example PCBs. Generally, PBDEs show higher concentrations in herring muscle in the Baltic compared to the Swedish west coast in the North Sea (Bignert et al. 2017). PBDEs seem to be declining in open sea areas, but the variation both between and within sites is larger in coastal areas (Result figure 2 and 3).

The monitoring has gaps in Estonian, Latvian and Russian waters. In other areas, e.g. Finland, the monitoring period is too short to evaluate the levels with high confidence.

Concentrations of several PBDEs in the marine environment are declining (Bignert et al. 2017). Concentrations of PBDE show decreasing trend in herring muscle from 5 monitoring stations in the Baltic Sea (results figure 2), but in coastal areas the trend is less clear (Results figure 3). 


Results figure 3.PNG

Results figure 3. Temporal trends of PBDEs concentration (ng/g wet weight – 5% lipid normalized) in herring muscle from stations Fladen Kattegat, Gdansk Basin, Bothnian Sea and  north Baltic Proper, (grey colour- confidence level 95% range (see Assessment protocol)). 


Confidence of the indicator status evaluation

The confidence of the status evaluation is considered high. Data is available from several regions covering a time period of several years.

 

Evaluation of secondary matrices

Concentrations of PBDEs has also been measured in sediments. The threshold value for sediment is 310 µg kg-1 dry weight (dw). This threshold value is high compared to the threshold value in biota. When these results are assessed against the QS for sediment all assessment units with data show a good status (Results figure 4).


PBDE_trend_sediment.pngPBDE_status_sediment.png

Results figure 4. Status assessment results (left) and assessment per station in the Baltic Sea (right) based on the evaluation of the indicator Polybrominated diphenyl ethers (PBDEs) in sediments. Green colour indicates that the upper 95 % confidence interval for PBDE concentrations are below the threshold value. Small open circles indicate a status assessment based on only 1-2 years of data. The assessment is carried out using Scale 4 HELCOM assessment units (defined in the HELCOM Monitoring and Assessment Strategy Annex 4). Click here to access interactive maps at the HELCOM Map and Data Service: PBDEs.