Data are submitted to the MERMAN database by Competent Monitoring Authorities. A series of templates are populated by submitting officers and submitted to the database which has in-built data restrictions and a data filter to ensure high quality, accurate data are submitted. The data filter has formulae in-built which use Accredited Quality Control information from known standards, limits, standard deviations and/or inter laboratory calibration exercises to calculate a score. Only data that pass a threshold agreed with the national advisory bodies are used for assessments.

The data for 1999 - 2019 were extracted from MERMAN on 30 March 2022. Further data checks were made and records with obvious errors were deleted or corrected. The concentration and biological effects data were standardised to agreed units and bases and, in the case of sediment, were normalised to 5% aluminium (metals) and 2.5% organic carbon (organics). The data were grouped into time series, typically of a single contaminant in a single species and tissue (biota) at a single monitoring station. Time series with no data in the period 2014 - 2019 were excluded. The data archived here are those for selected metals; polycyclic aromatic hydrocarbons (PAHs) and their metabolites; polychlorobiphenyls (PCBs), dioxins and other organochlorines; polybrominated diphenyl ethers (PBDEs) and other organobromines; organofluorines; tributyltin and its derivatives; imposex (VDS), ethoxyresorufin-O-deethylase (EROD), and other biological effects measurements.

The individual time series were assessed for status and trends. Status was assessed against environmental thresholds (biota and sediment) and human health thresholds (biota only). The results are archived here, with links to the underlying methodology included in the description of each resource.

The results of the individual time series were synthesised to assess status and trends at the biogeographic regional level. Results are archived for metals, PAHs, PCBs and PBDEs in biota and sediment, and for PAH metabolites, imposex and EROD in biota.