This pre-core test indicator and its threshold values are yet to be commonly agreed in HELCOM and the presented thresholds are furthermore not currently approved EQS values, but provisional proposals. The indictor is included as a test indicator for the purposes of the 'State of the Baltic Sea' report, and the results are to be considered as intermediate.
Diclofenac can be analysed in water and in fish plasma, and other biomarkers are rapidly being developed. Pharmaceuticals are generally present at very low concentrations in the environment, thus it is vital that selected analytical methods take analytical limits into consideration (see Unesco and HELCOM, 2017 for discussion). Agreement on methodology and the analytical procedure to carry out the designated analysis will be convened on by HELCOM Contracting Parties during further indicator development.
The HELCOM BASE pilot project carried out sampling in waste water treatment plants according to the following methodology:
Diclofenac is currently not included in the regular environmental monitoring of any HELCOM Contracting Party, though EU member states have been obliged to monitor this substance and report collated data due to its inclusion on the first watch list of the EU priority substances. This process has now been completed and the data review and decision making process are underway. The substance is considered an emerging issue, and as such it has been included in some national screening programmes (e.g. Swedish EPA) and as extensive spatial and temporal data is reported this indicator will be updated.
Due to the lack of coherent data from the marine environment and especially from biota, it is not possible to give recommendations on optimal monitoring at this time. Generally it can be stated that monitoring should be commenced in coastal areas close to cities with large wastewater treatment plants (WWTPs), particularly those within the coastal zone, and that intercalibration between all involved laboratories would be very beneficial.
Screening studies of surface water show concentrations generally dropping to below the threshold value at a distance of 10 km from WWTPs. It might be appropriate to monitor concentrations at the WWTP and at a specified distance from the plant in sea water and biota, however specifying the distance will require further work. The change of diclofenac concentration over a distance from source is highly dependent on the hydrological, hydro-chemical and hydro-biological regimes in the assessment unit. It might not be possible to provide guidelines as the appropriate design of the sampling strategy that would be generally applicable in all areas. However, it could be relevant to consider more closely the patterns in changing concentrations versus distance from source from several locations, to consider whether min-max and median values at a certain location or from several locations could be used when evaluating the status of the environment. Examining concentration trends over time more closely is also considered to be relevant.
The pilot study in the St Petersburg area carried out in the HELCOM BASE project (HELCOM 2014) clearly demonstrated the benefit from coupling environmental monitoring data with proxy data from pharmaceutical sales. However the pilot study underlines the importance of accessing high quality sales data for making relevant proxy evaluations. Improving the availability of this proxy data from pharmaceutical sales, would be a cost effective method to improve the knowledge base of the environmental status assessment of the Baltic Sea.