Environ Sci Pollut Res 
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et al. 2010, 2012; Lewis et al. 2012). Effect levels for such 
chronic effects are presently not available for most 
micropollutants. Most of the detected concentrations are below 
environmental assessment criteria, as far as criteria are set at all. 
However, the detected concentrations within this study are well 
above background values, which should be zero for a possible 
chronic effect of the pollutant load anthropogenic substances and 
above concentrations, which are observed in other open sea 
areas, such as the open North Sea. Encouraging is that decreasing 
concentrations of several micropollutants over the investigation 
decade could be observed and that their single concentrations 
currently only pose a low risk. 
Conclusion and recommendations 
Results demonstrate that there is a multihide of mid-polar organ 
ic micropollutants present in the Baltic Sea. In addition to the 
well-known “classical” pollutants, like PCBsor PAHs, organic 
micropollutants are currently an unidentified burden to the ma 
rine environment. Due to their mostly polar character, they are 
detectable in the water phase, where their concentrations out 
range the classical pollutants by up to three orders of magnitude 
(Naumann et al. 2020). Nevertheless, the current monitoring 
programs are lacking observations of the investigated 
micropollutants, and thus should be updated in the near future. 
The spatial distribution of the investigated micropollutants is 
homogenous throughout the Baltic Sea. A slight decrease in con 
centration is observed for most compounds from west to east, 
with the lowest values in the Bothnian Sea. At the station PB1-3, 
close to the mouth of the Odra, concentrations of some pollutants 
show high values indicating a riverine input. In summer, locally 
elevated concentrations of some herbicides were observed at 
coastal stations in the western Baltic Sea (coast of Schleswig- 
Holstein), and to a lesser extent in the Gulf of Finland. 
Additionally, 2,4-D concentration is high at a region north of 
the Darss and at the Arkona Basin. The observed time trends 
are quite different for individual micropollutants. Those com 
pounds which exhibit no direct current inputs (e.g., ATR, SIM, 
PFOA, PFOS) show downward directed time trends, demonstrat 
ing the success of the reduction measures taken in the past. 
Several herbicides (e.g., DIU, 2,4-D) show highly seasonal influ 
ences with elevated concentrations during summertime and high 
local and temporal variabilities. For these compounds, no trend is 
detectable. Remarkably, for some compounds (e.g., PFHXA, 
PFHPA, TERB, METOLA), slightly increasing trends can be 
identified, showing a new negative impact possibly replacing 
restricted pollutants. 
The presented results showed the following gaps; the sea 
sonal coverage was not at an optimum and should be im 
proved. For some compounds (e.g., herbicides), a seasonally 
influenced input is likely, as a consequence of their applica 
tion periods. To improve the interpretation, concerning 
pollution sources, the spatial range of investigation should 
be enlarged to the entire Baltic Sea, and the layered structure 
of the Baltic Sea should be represented in the sampling strat 
egy. Knowledge about the distribution of the contaminants 
could be improved by mathematical modeling, as most of 
the described polar compounds behave fairly conservative. 
Additional polar compounds are likely to be present in the 
Baltic Sea environment. Therefore, screening for new contam 
inants (e.g., pharmaceuticals, hormones, and antibiotics) 
should be encouraged, and the monitoring programs should 
be adapted. A large lack exists concerning the chronic ecolog 
ical evaluation of the observed concentrations of the 
micropollutants. Hence, research concerning eco- 
toxicological data for chronic effects of single compounds or 
mixtures in the marine environment is needed. 
Supplementary Information The online version contains supplementary 
material available at https://doi.org/10.1007/s 11356-021-13254-5. 
Acknowledgements Special thanks are to Elke Hammermeister (BSH) 
and Ines Hand (IOW) for their engagement and skillful work during 
sampling and analysis and Jana Appelt (former IOW) for her help with 
the data screening. 
Author contribution Kathrin Fisch: data analysis, formal analysis, writ 
ing draft, review and editing 
Berit Brockmeyer: review and editing 
Wolfgang Gerwinski: investigation, methodology, data analysis and 
evaluation - review and editing 
Detlef E. Schulz-Bull: investigation, project administration, supervi 
sion, review and editing 
Norbert Theobald: investigation, project administration, supervision, 
methodology, data analysis and evaluation, writing, review and editing 
Funding Open Access funding enabled and organized by Projekt DEAL. 
This research was part of the monitoring programs ofthe Leibniz-Institute 
for Baltic Sea Research Wamemunde and the Federal Maritime and 
Hydrographic Agency Germany. No additional funding was received. 
Availability of data and materials All data generated or analyzed during 
this study are included in this published article and its supplementary 
information files. 
Declarations 
Ethics approval and consent to participate Not applicable. 
Consent for publication Not applicable. 
Conflict of interest The authors declare no competing interests. 
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