Hazardous substances in marine organisms in Europe's seas

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.

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).

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.

Supporting information

Definition

The indicator is based on concentrations of nine hazardous substances measured in eight species of mussels and oysters. The nine substances are cadmium (Cd), mercury (Hg), lead (Pb), Copper (Cu), hexachlorobenzene (HCB), lindane (gamma-hexachlorocyclohexane, HCHG), DDT (using the breakdown product p,p'-DDE; DDEPP), benzo[a]pyrene (BAP) and 2,3',4,4',5-Pentachlorobiphenyl (CB118). For each station, the 90% percentile over the 10 year period 2010-2021 was used to classify concentrations in ‘low’, ‘moderate’ and ‘high’ classes. These classifications are based on OSPAR's Background Assessment Concentrations (BAC) criteria, the Environmental Quality Standards (EQS) from the EU Water Framework Directive (WFD) and the Maximum Permissible Concentration (MPC) for food.

Methodology

Concentrations of the nine hazardous substances were collected from two databases: ICES (www.ices.dk) and EMODNET Chemistry (https://www.emodnet-chemistry.eu/). The databases contain measurements for a large number of species, but to achieve a relatively homogenous dataset, only data from bivalves of the following species were used: Cerastoderma edule (common cockle), Mya arenaria (softshell clam), Ruditapes philippinarum (Manila clam), Mytilus edulis (blue mussel), M. galloprovincialis (Mediterranean mussel), Crassostrea gigas (Pacific oyster), Ostrea edulis (native oyster) and Macoma balthica (Baltic clam). This left us with approximately 300,000 measurements. Approximately 10% of the stations had data in both databases and needed database cleaning to avoid using the same measurement from both databases. Furthermore, only data from the late summer and autumn were used, as concentrations of mussels in the spring are affected by spawning. For status, the 90% percentile over the 10 year period 2010-2021 was used to classify concentrations in 'low', 'moderate', and 'high' classes using two threshold values per contaminant (some thresholds also differ between blue mussels and oysters). The lower of the two thresholds was mostly OSPAR's BAC criterion; the EQS for cadmium and mercury was used. The higher threshold value was either the EQS from the WFD or MPC for seafood security. In order to calculate status, at least one year (Mediterranean) or three years (other areas) of data since 2010 were needed. For trends, dry-weight concentrations for metals and wet-weight concentrations for organic substances were used. Data before 2005 were excluded and trends were calculated for time series of 5-10 years that ended in 2015 or later. If the data series had no median concentrations under LOQ, we used linear regression; otherwise, a Bayesian model (with non-informative priors) implemented in JAGS (Plummer 2021) was used.

Database extractions taken in 2022 were used. However, due to the time lag in reporting, most data series stopped in 2021 — so the analysis was restricted to the period 2010-2021.

Policy/environmental relevance

The MSFD websitestates that ‘human activities affect the marine environment through the release of chemical contaminants, which degrade the state of marine waters and can cause serious damage to its functioning’. The indicator is based on bivalves, which live as water filterers and are very effective ‘harvesters’ of any contaminants found in the water. In our process of selecting contaminants, we wanted to have contaminants that have been recorded in as many parts of Europe as possible — as well as contaminants that span a range of sources and behave differently in the environment. For instance, mercury is very volatile, which makes the atmosphere (including rain) an important source. Many of the other contaminants are mostly found in the aquatic environment. Many of the contaminants — such as DDT, lindane — represent ‘legacy’ contaminants. These are now largely banned but still exist in the environment, including in ocean sediments.

Accuracy and uncertaintiesData sources and providers

Metadata

DPSIRTopicsTagsTemporal coverageGeographic coverage

TypologyUN SDGsUnit of measureFrequency of dissemination

References and footnotes

Noman, M. A., Feng, W., Zhu, G., Hossain, M. B., Chen, Y., Zhang, H. and Sun, J., 2022, 'Bioaccumulation and potential human health risks of metals in commercially important fishes and shellfishes from Hangzhou Bay, China', Springer Science and Business Media LLC.

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EEA, 2011, Hazardous substances in Europe’s fresh and marine waters: an overview., Publications Office of the European Union, Luxembourg.

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EU, 2013, Directive 2013/39/EU of the European Parliament and of the Council of 12 August 2013 amending Directives 2000/60/EC and 2008/105/EC as regards priority substances in the field of water policy, OJ L 226, 24.8.2013, p. 1–17.

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Dietz, R., Fort, J., Sonne, C., Albert, C., Bustnes, J. O., Christensen, T. K., Ciesielski, T. M., Danielsen, J., Dastnai, S., Eens, M., Erikstad, K. E., Galatius, A., Garbus, S.-E., Gilg, O., Hanssen, S. A., Helander, B., Helberg, M., Jaspers, V. L. B., Jenssen, B. M. et al., 2021, 'A risk assessment of the effects of mercury on Baltic Sea, Greater North Sea and North Atlantic wildlife, fish and bivalves', Environment International 146, pp. 106178 (
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EC, 2006, Commission Regulation (EC) No 1881/2006 of 19 December 2006 setting maximum levels for certain contaminants in foodstuffs (Text with EEA relevance), OJ L.

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Efsa, P. C. F. C., Knutsen, H., Alexander, J., Barregård, L., Bignami, Bruschweiler, Ceccatelli, Cottrill, Dinovi, Edler, Grasl-Kraupp, Hogstrand, Nebbia, Oswald, Petersen, Rose, Roudot, Schwerdtle, Vleminckx et al., 2018, 'Risk for animal and human health related to the presence of dioxins and dioxin???like PCBs in feed and food', Wiley.

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Hazardous substances in marine organisms in Europe's seas

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

Figure 2. Concentrations of CB118 relative to assessment criteria

Supporting information

Metadata

References and footnotes