OSPAR 2022 — Pb, Cd, and Hg status and trend assessment in Northeast Atlantic fish, shellfish, and sediment (1979-2020)

The OSPAR Common Indicator Assessment evaluates the status and temporal trend of mercury (Hg), cadmium (Cd), and lead (Pb) — with extended coverage of zinc (Zn), copper (Cu), chromium (Cr), nickel (Ni), arsenic (As), cobalt (Co), silver (Ag), tin (Sn), and selenium (Se) — measured in fish, shellfish, and sediment across the OSPAR Convention area (Northeast Atlantic) for the 2023 Quality Status Report. The assessment finds that lead concentrations in fish and shellfish are above background levels in most areas, mercury is above the EU Environmental Quality Standard for secondary poisoning (QS_sp) throughout all assessed subregions, and cadmium is above background in the Celtic Seas, Iberian Sea, and Northern Bay of Biscay. Despite bans and the Minamata Convention on Mercury, biota concentrations are mostly increasing — particularly in OSPAR Region II (Greater North Sea) — while sediment concentrations are often above the NOAA Effects Range-Low (ERL) environmental threshold but decreasing in most subregions. The assessment uses the CEMP dataset held at the ICES Data Centre, processed via the online OHAT assessment tool with a linear mixed model fitted across contaminants assessment areas.

Key numbers

Assessment criteria used (Table a, page 10)

Sediments (mg/kg dw):

Biota (µg/kg, mussels and oysters dw; fish, QS_sp, and MPC ww):

Table a notes (page 10): BAC for sediment is normalised to 5% aluminium except for subregions Iberian Sea and Gulf of Cadiz. ERLs are not normalised but considered valid for 5% aluminium. BACs for mussels and oysters are expressed as µg/kg dw and BACs for fish, QS_sp, and MPC are expressed as µg/kg ww. Cadmium BAC for fish is only applied when lipid > 3% and mercury BAC for fish was above QS_sp so not used. The reported BAC for mercury in mussels is 90 µg/kg dw; an EC EQS of 20 µg/kg ww for whole fish is below the established BAC for mercury of 35 µg/kg ww in fish, so for fish, BACs are not used and QS_sp is used directly.

Monitoring effort (Table b, pages 10-11)

Number of monitoring sites per assessment area used in regional status and trends. Asterisk denotes regions with insufficient stations for regional estimates.

Status results — mercury in fish and shellfish relative to QS_sp (Figure 3, page 13)

The QS_sp for mercury in whole fish is 20 µg/kg ww. The assessment combined fish and shellfish using a statistical model that adjusts shellfish concentrations to fish levels. Mean mercury concentration relative to QS_sp was above the threshold (red, above environmental criteria) in every subregion assessed; visually read from Figure 3 the ratios are approximately:

All assessment-area-level mean concentrations were above the QS_sp; no regions were significantly below this threshold (page 12). No EC MPC exceedances are reported at the regional aggregate level for mercury in fish muscle (the human-health MPC is 500 µg/kg ww, well above QS_sp).

Status results — Pb, Cd, and Hg in fish and shellfish relative to BAC (Figure 4, page 13)

Visual read of Figure 4 (mean concentration relative to Background Assessment Concentration; blue = below background, red = above environmental criteria, green = below environmental criteria but above background):

• Cadmium below BAC in Irish and Scottish West Coast, Celtic Sea, Northern Bay of Biscay, Iberian Coast, Gulf of Cadiz (5 subregions); above BAC elsewhere.
• Lead below BAC in Greenland-Scotland Ridge, Norwegian Sea, Irish and Scottish West Coast (3 subregions); above BAC elsewhere.
• Mercury above BAC in all assessed subregions where data are available.

Status results — sediment relative to ERL (Figure 5, page 13)

For sediments, all subregions with data were statistically significantly below the ERL for cadmium. For mercury and lead, only the Northern North Sea, Irish and Scottish West Coast, and Iberian Sea were below the ERL; all other subregions (Southern North Sea, English Channel, Irish Sea, Celtic Sea, Iberian Coast for lead and mercury depending on subregion) were above. In the Channel and Southern North Sea, adverse biological effects on marine organisms from trace metals cannot be ruled out.

Trend results — fish and shellfish (Figure 6, page 14)

Modelled yearly change in concentration from 2000-2020 (or 2010-2020 for the headline % change). Key trends:

• Mercury in fish and shellfish: no decreasing trends in any subregion; increasing trends of approximately 2 to 4% yearly change in the Southern North Sea, English Channel, and Northern Bay of Biscay.
• Lead in fish and shellfish: increasing approximately 4% yearly change in the English Channel; approximately 1.5% yearly change in the Southern North Sea and Northern Bay of Biscay.
• Cadmium in fish and shellfish: increasing approximately 2.5 to 3.5% yearly change in the Channel; approximately 1.5% yearly change in the Southern North Sea and Northern Bay of Biscay.

The increasing biota trend in the Southern North Sea is mainly driven by the Wadden Sea area; the Channel and Northern Bay of Biscay trends are mainly along the French coast.

Trend results — sediment (Figure 7, page 14)

• Mercury in sediment: decreasing in the Northern North Sea, Southern North Sea, and the Irish Sea and Irish and Scottish West Coast at approximately -3% yearly change. No subregions with available data showed increasing mercury in sediment.
• Lead in sediment: decreasing approximately -2% yearly change in the Southern North Sea and Irish Sea.
• Cadmium in sediment: increasing 4-5% yearly change in the Channel and Irish and Scottish West Coast; decreasing approximately -2.5% yearly change in the Southern North Sea.

Extended results — secondary metals (pages 15-17)

Status assessment for zinc and copper in biota was above background in all OSPAR Regions (Figure c, page 15). For sediments, zinc and chromium were above the ERL in most of the central North Sea (Southern North Sea, English Channel, Irish Sea, Celtic Sea, and Irish and Scottish West Coast for chromium). Copper exceeded the ERL only in the Celtic Seas. Levels for the Northern North Sea and Iberian Sea were below the ERL for zinc and chromium.

Time trends for additional metals in biota (Figure e, page 17): increasing trends were found in the Channel and Southern North Sea for zinc, selenium, copper, and arsenic. Only the Channel showed increasing trends for nickel and chromium in biota. The Northern Bay of Biscay showed increasing concentrations for zinc, nickel, copper, and chromium. Time trends in sediment (Figure f, page 17): decreasing trends in nickel, zinc, copper, arsenic, and chromium for the Southern North Sea. Only arsenic (Northern North Sea) and cadmium (English Channel and Irish and Scottish West Coast) showed increasing trends in sediment among the secondary metals.

Conclusion summary (page 18)

Mercury was found to be problematic in all areas for shellfish and fish, being above both the BAC for mussels and the QS_sp assessment criteria. Lead and cadmium were above background levels for shellfish and fish in most areas, except the Irish and Scottish West Coast. The Celtic Seas, Iberian Sea, and Northern Bay of Biscay were above background levels for cadmium, and the Norwegian Sea and Greenland-Scotland Ridge for lead. In sediments, mercury and lead were above the ERL assessment criteria in the Southern North Sea, the Channel, the Irish Sea, and the Celtic Seas; for the Irish and Scottish West Coast, background levels were achieved in sediments.

Evidence Fitness

This is an A-tier intergovernmental status and trend assessment that provides regulator-grade occurrence and trend statistics for Pb, Cd, and tHg in fish muscle, mussel and oyster soft body, and sediment across 15 subregions of the Northeast Atlantic for the 1979-2020 period (with the status assessment focused on 2015-2020). It supports product-category occurrence claims for marine non-predatory fish (the OSPAR CEMP species mix), shellfish (Mytilus, Crassostrea oysters), and seafood in the European market. It supports regulatory-context claims for the EU Water Framework Directive QS_sp for mercury (Directive 2013/39/EU), the European Commission Regulation 1881/2006 maximum permissible concentrations (MPC) for lead, cadmium, and mercury in fish muscle, bivalves, and crustaceans, and OSPAR Background Assessment Concentrations. Statistics are modelled means with 95% confidence intervals from a linear mixed model fitted across OSPAR contaminants assessment areas; downstream synthesis should preserve the model-mean basis rather than treat the values as raw measurement means. The 2022 assessment supersedes the OSPAR Intermediate Assessment 2017 (IA 2017); time-trend continuity with IA 2017 is documented in the report (Conclusion extended, page 19), with the observed shift from majority-decreasing lead trends in IA 2017 to majority-stable or increasing trends in 2020 being one of the report’s headline findings. Public evidence label: Reconstructable dataset (CEMP via ICES Data Centre and OHAT online tool).

Methods (brief)

Source data: Coordinated Environmental Monitoring Programme (CEMP) dataset, hosted at the International Council for the Exploration of the Sea (ICES) Data Centre. 603 to 647 biota monitoring sites and 393 to 401 sediment monitoring sites contributed data; the status assessment focused on stations with data available from 2015 onward (389 biota stations). Trend assessment was restricted to stations with at least 5 years of data (66-70 stations for mercury, cadmium, and lead).

Sample matrices and basis:

• Biota: mussels (BAC 90 µg/kg dw for Hg, 960 µg/kg dw for Cd, 1300 µg/kg dw for Pb), oysters (BAC 180 µg/kg dw for Hg, 3000 µg/kg dw for Cd, 1300 µg/kg dw for Pb), and fish whole-fish for the QS_sp comparison (20 µg/kg ww for Hg). Fish muscle is the basis for the EC MPC comparison (500 µg/kg ww for Hg and Cd-free at 50 µg/kg ww; Pb at 300 µg/kg ww in fish muscle).
• Sediment: total metal concentrations, normalised to 5% aluminium (except for the Iberian Sea and Gulf of Cadiz subregions, where sediments are coarser and not derived from glacial clays). Expressed in mg/kg dw.

Mercury was measured as total mercury in biota and sediment; the report explicitly notes that the QS_sp value is “mainly derived from methylmercury but applied to total mercury” (page 7). The OSPAR speciation discipline does not separate inorganic and methylmercury at the CEMP-level assessment, so frontmatter and synthesis carry tHg per CLAUDE.md Part 14. Arsenic in the secondary-metal extended results is total arsenic (tAs); no inorganic-arsenic speciation is reported. Chromium in the extended results is total chromium (Cr), no Cr-VI speciation. Tin in the extended results is total tin (Sn); no organotin speciation is reported in the trend figures.

Statistical method: For each trace metal at each monitoring site, the time series of concentration measurements was assessed for trends and status using the methods described in the OHAT online assessment tool (https://dome.ices.dk/ohat/?assessmentperiod=2022). Individual time-series results were synthesised at the assessment-area scale via meta-analyses. The trend in each metal at each monitoring site was summarised by the estimated annual change in log concentration, with its associated standard error. The annual change in log concentration was then modelled by a linear mixed model with fixed effects of trace metal and OSPAR contaminants assessment area, and random effects of monitoring site (biota only) and metal-by-monitoring-site interaction plus residual variation. Status at the assessment-area scale was summarised as the log ratio of the fitted concentration in the last monitoring year to the QS_sp, and to the BAC. The QS_sp analyses also included a term to estimate and adjust for the difference in concentrations between fish and shellfish (implicitly accounting for trophic level via a statistical model rather than measured trophic level).

Spatial unit: OSPAR Regions and subregions as defined in the OSPAR Convention. Region I (Arctic Waters), Region II (Greater North Sea), Region III (Celtic Seas), Region IV (Bay of Biscay and Iberian Coast). For trend and status assessment, only subregions with at least three monitoring sites and reasonable geographic spread were included, reducing coverage from 15 to 14 subregions for fish and shellfish and seven for sediments.

Quality assurance: the CEMP dataset is maintained at the ICES Data Centre with national contracting-party laboratories under OSPAR’s monitoring quality framework; specific QA protocols are described in the CEMP Assessment Manual (OSPAR, 2008, updated MIME 2020 and 2021) referenced in the report.

Limitations stated in the report: assessment thresholds are not fully harmonised — there is only an EU EQS available for mercury in biota under the Water Framework Directive, and no environmental thresholds for cadmium and lead in fish and shellfish, requiring use of human-health-based EC MPC values as a proxy environmental criterion (page 8). Two alternative thresholds for marine mammals and birds developed by the Arctic Monitoring and Assessment Programme (Dietz et al. 2021) were not included in the regional status assessment because further work is required to investigate their comparability with the BAC and QS_sp. The use of dietary standards for environmental risk assessment is acknowledged by the authors as not fully satisfactory and the conclusions are noted as needing to be treated with care (page 8).

Implications

• Certification: the OSPAR QSR 2023 assessment is a regulator-grade occurrence and trend source for fish-marine-non-predatory and shellfish categories in the Northeast Atlantic. It establishes that mercury in Northeast Atlantic fish and shellfish exceeded the EU QS_sp (20 µg/kg ww in whole fish) in every assessed subregion; ratios above QS_sp range from approximately 1 in the Greenland-Scotland Ridge and Gulf of Cadiz to approximately 5.5 in the Northern North Sea. The report contributes occurrence-trend data on the direction of change since the IA 2017: mercury, cadmium, and lead in biota are increasing in three subregions each (Greater North Sea and Bay of Biscay coast), while cadmium and lead are decreasing in one subregion each. The increase in biota concentrations despite decreasing inputs and the Minamata Convention is the report’s most policy-relevant finding for occurrence work feeding into the Standards Workbench.
• Courses: illustrates a model-based intergovernmental assessment using a linear mixed model across heterogeneous national monitoring contributors, with explicit handling of trophic-level differences between fish and shellfish via a statistical adjustment rather than separate thresholds. Useful as a case study in how a multi-decade monitoring programme (CEMP since the 1980s) supports both status and trend conclusions, and in how human-health MPC values are used as proxy environmental criteria when ecological thresholds are unavailable.
• App: contributes occurrence data and recent trend direction for marine non-predatory fish and shellfish under European Northeast Atlantic sourcing. Mercury values relative to the QS_sp threshold are an order-of-magnitude indicator of contamination intensity by subregion, with the Greater North Sea consistently the most affected.
• Microbiome: not applicable (status and trend assessment, no microbiome data).

Provenance notes

PDF retrieved as part of the Kimi Agent Download Corruption Issue manual-fetch batch; this is the 22-page OSPAR Common Indicator Assessment included in the OSPAR Quality Status Report 2023 (lead authors Martin Mørk Larsen and Dag Øystein Hjermann; chapter year 2022 per the formal citation). Karen’s suggested handle KADC_metals-lead-cadmium-and-mercury-in-fish-shellfish- is preserved verbatim. Cite-key follows the corporate-author + year + short-slug convention applied to helcom2017-core-indicator-metals-baltic (the parallel Baltic-Sea sibling assessment), here ospar2022-metals-fish-shellfish-sediment. License recorded as public-redistribute per OSPAR Commission’s standard QSR access terms. The OSPAR QSR 2023 is the successor to the OSPAR Intermediate Assessment 2017, which used the same monitoring programme but with a smaller dataset and a different baseline year for trend modelling; downstream synthesis should not double-count IA 2017 and QSR 2023 as independent assessments of the same dataset.

The report is the OSPAR-area sibling to helcom2017-core-indicator-metals-baltic (HELCOM Core Indicator for the Baltic Sea, 2011-2015 assessment period). Where both sources cover Region II (Greater North Sea) and the Kattegat (an OSPAR Skagerrak-and-Kattegat subregion that is also in HELCOM’s southwestern Baltic), they describe the same monitoring sites under different intergovernmental commissions; downstream synthesis should treat the two reports as overlapping rather than independent for those subregions.

Sediment threshold values are reported with European-style decimal commas in the original Table a (e.g., “0,31” for Cd BAC in mg/kg dw); these have been faithfully transcribed using standard decimal points in this page (0.31 mg/kg dw, etc.) following CLAUDE.md Part 14 number convention.

Verification notes

• Audit subagent (2026-06-03) flagged the cadmium trend attribution in “Trend results — fish and shellfish” as incorrectly stretching the 2.5-3.5% yearly-change rate to the Channel + Southern North Sea + Northern Bay of Biscay collectively; verified against PDF page 14 (“around 2,5 to 3,5% yearly change for cadmium and 4% yearly change for lead in the Channel and ~1,5% yearly change in the Southern North Sea and Northern Bay of Biscay”). The 2.5-3.5% rate applies to cadmium in the Channel only; the Southern North Sea and Northern Bay of Biscay rate is ~1.5%. Corrected.
• Audit subagent (2026-06-03) flagged Se (selenium) in frontmatter metals: as outside the closed slug vocabulary (no wiki/metals/selenium.md page exists). Verified: confirmed absent from taxonomy snapshot and from wiki/metals/ directory. Dropped Se from frontmatter. The report discusses selenium briefly in Figure e (page 17) and the extended results (Northern Bay of Biscay increasing trend for selenium-zinc-nickel-copper-chromium; Channel and Southern North Sea increasing trends for zinc-selenium-copper-arsenic) but the absence of a taxonomy slug means the source’s selenium contribution is not routed to a metal page. Surface to Karen as a candidate for taxonomy expansion if downstream synthesis identifies further selenium-relevant sources.
• Audit subagent (2026-06-03) suggested extending matrices: to include whole-fish since the QS_sp comparison is stated for “whole fish”; verified against PDF — false positive. Actual CEMP measurements are fish muscle, with shellfish statistically adjusted to fish levels via a model. fish-muscle is the faithful measurement-basis matrix; whole-fish would imply a measurement basis not present in the underlying data.
• Audit subagent (2026-06-03) noted Figure 3 mercury/QS_sp ratios are visual reads from a log-scale plot; preserved as approximate ranges and flagged in the Key numbers table caption.

Wiki pages updated on ingest

• lead
• cadmium
• mercury
• mercury-total
• copper
• zinc
• chromium
• nickel
• arsenic-total
• cobalt
• silver
• tin
• fish
• white-fish
• bivalve-molluscs
• seafood
• fish-marine-non-predatory
• shellfish
• seafood
• eu-1881-2006-contaminants-superseded
• eu-reg-2022-617-mercury-fish

Page history

The five most recent substantive edits to this page. The full version history lives in git; when DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.