Hazardous substances are polluting Europe's seas, posing risks to ecosystems and human health. Between 2010 and 2021, nine hazardous substances were monitored in marine organisims, all exceeding safe limit values. High levels were observed for benzo[a]pyrene, DDE (a breakdown product of DDT), and polychlorinated biphenyl (PCB). Few time trends show more decreasing concentrations (improvements) than increasing ones, except for mercury. Further actions are essential to meeting the targets outlined in both the Marine Strategy Framework Directive and the Zero Pollution Action Plan.

Figure 1. Hazardous substances in mussels and oysters in Europe's seas

Hazardous substances in mussels and oysters in Europe's seas

In the marine environment, hazardous substances accumulate in fish and shellfish, which are a food source for marine life, wildlife and humans. These contaminants are toxic for marine biota, and consuming contaminated seafood may generate adverse effects on human health such as organ failure, neurological disorders and increased cancer risk.

While evidence suggests a stabilisation in concentrations, it is imperative to implement measures such as stringent regulatory enforcement and promote safe and sustainable alternatives, aimed at preventing generation of hazardous chemicals and reducing emissions at their source. Reducing concentrations of these substances helps achieve the MSFD Good Environmental Status and the targets set in the Zero Pollution Action Plan.

Classifications of hazardous substances measured in mussels and oysters between 2010-2021 are summarised below (also Figure 1). Concentrations were classified by Environmental Quality Standards (EQS) in biota where available; and OSPAR Background Assessment Concentrations (BAC) criteria and Maximum Permissible Concentrations (MPC) for humans were used to set the upper limit for the 'low' and 'moderate' classes, respectively.

The North-East Atlantic (NEA) Ocean and Mediterranean Sea generally demonstrate moderate to low levels of hazardous substances, with some high concentrations. The Baltic Sea leans towards moderate levels for most contaminants. Overall, the NEA Ocean and Mediterranean Sea appear to have relatively lower concentrations of certain hazardous substances compared to the Baltic Sea. However, the presence of high concentrations still indicates ongoing challenges. The Baltic Sea stands out with more consistent moderate levels across various substances, suggesting a less favorable status compared to the NEA Ocean and Mediterranean Sea.

Time trends show decreasing concentrations are more frequent than increasing ones, whereas decreasing trends represent lower concentrations found in marine organisms, and an improved status. While decreasing trends are promising, the prevalence of unknown and no (discernible) trends makes it difficult to conclusively determine if the situation is improving.

Assessment of one PCB (dioxin-like CB118) showed mainly ‘high’ in all regions. A significant part of the concentrations was classified as ‘moderate’. PCBs continue to pose a threat to marine ecosystems (Figure 2).

Figure 2. Concentrations of CB118 relative to assessment criteria

Concentrations of CB118 relative to assessment criteria

Figure 2 shows details of assessments of CB118 in bivalves, i.e. blue mussel (Mytilus edulis and Mytilius galloprovincialis) and oysters (almost always Crassostrea gigas), during 2010-2021, with BAC and EQS indicated. Boxplots show a large percentage of the ‘high’ classifications (red points) exceed the EQS many times. The Western Mediterranean, Greater North, Celtic and Baltic Seas all had stations where concentrations of CB118 in mussels were more than 10 times the EQS. The dioxin-like PCBs are also toxic to humans, and in 2018, the European Food Safety Authority set a tolerable weekly intake of dioxins and dioxin-like PCBs for humans . PCBs are typically transferred through the consumption of contaminated food, particularly meat, fish, and dairy .

Figure 2 shows time trends for MSFD regions that had ample data for trend assessment. The Greater North and Celtic Seas had a significant decrease in concentrations during this period. The estimate of the decrease is ca. 25% per decade. For the Bay of Biscay and Baltic Sea, time series contained measurements under the detection limit, hence trends were not significant. Data were not sufficient for trend analysis in remaining areas.