Hazardous substances

The status of hazardous substances shows some signs of improvement during the assessment period, however it is still clearly not good (Figure 4.7). The integrated contamination status of the Baltic Sea remained above acceptable minimum levels during 2016-2021. The contamination status was assessed as either bad or poor in roughly 80% of the 57 assessed spatial units, including the majority of the open sea sub-basins. Only one assessment unit in the open sea had good status. The results partly reflect the prevailing monitoring regimes, because units achieving better status tend to be represented by fewer parameters being evaluated or key drivers of the overall status being absent.

Furthermore, only a small fraction of all potentially hazardous substances is measured and included in the indicator evaluations that make up the integrated assessment.

There are some encouraging signs, however. Six open sea sub-basins have improved their status category since the previous assessment (HELCOM 2018), although they are still not in good status. Furthermore, at the level of individual monitoring stations, there are more substances with downward concentration trends than upward trends.

The assessment results are mostly driven by elevated concentrations of polybrominated diphenyl ethers (PBDEs) in biota, tributyltin (TBT) in sediments, mercury in biota, and copper in sediments. Cadmium concentrations in biota and sediments also contribute, as do lead concentrations in biota.