Collection of over of 1129 datasets on contaminants in the ADRION area with free (38%) or licenced (56 %) access for the 94 % of the datasets. HarmoNIA data portal provides information on legacy pollutants such as heavy metals (929 data sets) and hydrocarbons (497 datasets) as well as on antifoulants (429 data sets), pesticides and biocides (330 data sets), polychlorinated biphenyls (187 datasets) and fertilizers (22 data sets). Information is available for all environmental matrices (seawater, sediment and biota). The data access system is built on the well consolidated EMODnet Chemistry approach.