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The report summarises the monitoring activities within the National Swedish Contaminant Programmefor freshwater biota. Each monitored contaminant has been examined in pike, perch or Arctic char from32 lakes from the north to the south in Sweden.No general trend could be seen for mercury, and all samples were above the EU threshold. Lead wasgenerally decreasing and concentrations were below the target level in all lakes. Cadmiumconcentrations showed no consistent trends over the monitored period, and cadmium concentrationswere below the target level in all lakes. Chromium concentrations are below the limit of quantification(LOQ) in most lakes after 2010. For nickel, arsenic, copper, zink, silver, and aluminium there were noclear temporal trends, with both upward and downward trends. Tin concentrations were below the LOQfor most sampling sites and throughout all years of sampling.In general, downward trends were seen for; PCBs, HCHs, DDT, DDE and PCDD/Fs in all species (with afew exceptions). The chlorinated compounds generally showed a somewhat higher concentration in thesouthern parts of Sweden. Most chlorinated compounds were below the suggested target levels.No general trend was seen during the monitoring period for PBDEs. However during the most recent 10year period, downward trends were seen in pike from Bolmen. The concentration of HBCDD was underLOQ in a majority of the samples.Several of the perfluorinated carboxylic compounds showed a non-linear increase in concentration inarctic char, while no trend was seen for PFOS. In perch, PFOS has decreased since 1980 while upwardtrends were seen for several carboxylic acids from 1980. Higher concentrations of perfluorinatedcompounds can in general be seen in the southern part of Sweden. In all lakes, PFOS is below thetarget level for all species.

The report summarises the monitoring activities within the National Swedish Contaminant Programme for freshwater biota. Each monitored contaminant has been examined in pike, perch or Arctic char from 32 lakes from the north to the south in Sweden. No general trend could be seen for mercury, and all samples were above the EU threshold. Lead was generally decreasing and concentrations were below the target level in all lakes. Cadmium concentrations showed no consistent trends over the monitored period, and cadmium concentrations were below the target level in all lakes. Nickel, arsenic, and copper showed upward trends in 30-50 % of the sampling sites. For zink, silver, and aluminium there were no clear temporal trends. Tin concentrations were below the limit of quantification for most sampling sites and throughout all years of sampling. In general, downward trends were seen for; PCBs, HCHs, DDT, DDE and PCDD/Fs in all species (with a few exceptions). The chlorinated compounds generally showed a somewhat higher concentration in the southern parts of Sweden. Most chlorinated compounds were below the suggested target levels. No general trend was seen during the monitoring period for PBDEs. However during the most recent 10 year period, downward trends were seen in pike from Bolmen. The concentration of HBCDD was under LOQ in a majority of the samples. Several of the perfluorinated carboxylic compounds showed an increase in concentration in arctic char, while no trend was seen for PFOS. In perch, PFOS has decreased since 1980 while upward trends were seen for several carboxylic acids from 1980. Higher concentrations of perfluorinated compounds can in general be seen in the southern part of Sweden. In all lakes, PFOS is below the target level for all species.

Within the Swedish National Monitoring Programme for Contaminants in Freshwater Biota, perch, pike and Arctic char are being analysed from 32 lakes distributed all over Sweden. One of the main objectives of the monitoring has been to detect temporal trends in different areas and for different contaminants. However, the measured concentrations in biota can be affected by biological factors such as age, length, trophic position (TP), fat or dry weight content. A change in one or several of these variables over time, or even among specimens taken within the same year, is likely to result in an increased variation of the measured concentrations and hence in a lower chance of detecting a trend. The purpose of this study was to evaluate if an adjustment of contaminant time trends by primarily stable isotopes, but also other confounding factors can: A) reduce the individual and between-year variation and hence B) improve the likelihood of detecting temporal trends in time series for metals and organic contaminants. The study revealed an improvement in the likelihood of detecting a contaminant trend after adjustment of the data for almost all lakes and for all tested substances. For some lakes and substances, this improvement was substantial. Age seems to be an important confounding factor for metals and per- and polyfluoroalkyl substances. For lipophilic substances, fat content also appears to be an important factor in some lakes together with adjustments for carbon and nitrogen isotope ratios (d13C and d15N), which all reduced the variation in contaminant data. This suggests that there is a benefit of adjusting data on a regular basis in contaminant monitoring programmes in the future.

The report summarises the monitoring activities within the National Swedish Contaminant Programme for freshwater biota. Each monitored contaminant has been examined in pike, perch or Arctic char from 32 lakes from the north to the south in Sweden. No general trend could be seen for mercury, and all samples were above the EU threshold. Lead was generally decreasing. Cadmium concentrations showed no consistent trends over the monitored period, and cadmium concentrations in 2017 were below the suggested threshold in all lakes. Nickel showed a general upward trend in 30% of the perch lakes. Arsenic concentrations showed no general spatial pattern and were increasing in liver from Arctic char, pike and perch from approximately 50 % of the sampling sites. Tin concentrations decreased in the majority of the perch time series during the most recent ten years. For copper, no general spatial pattern existed for concentrations in perch and about one third of the monitored lakes showed an upward trend. No general trend was observed for silver and aluminum. In general, downward trends were seen for; PCBs, HCHs, DDT, DDE and PCDD/Fs in all species (with a few exceptions). The chlorinated compounds generally showed a somewhat higher concentration in the southern parts of Sweden. Most chlorinated compounds were below the suggested target levels. No general trend was seen during the monitoring period for PBDEs. However an indication of decreasing concentrations of PBDEs is seen in the most recent years. The concentration of HBCDD was under LOQ in a majority of the samples. Several of the perfluorinated carboxylic compounds showed an increase in concentration in arctic char, while PFOS and FOSA decreased. In perch PFOS has decreased since 1995. Higher concentrations of perfluorinated compounds can in general be seen in the southern part of Sweden. In all lakes, PFOS is below the target level for all species.

The report summarises the monitoring activities within the National Swedish Contaminant Programme for freshwater biota. Each monitored contaminant has been examined in pike, perch or Arctic char from 32 lakes from the north to the south in Sweden. No general trend could be seen for mercury, and all samples were above the EU target level. Lead was generally decreasing. Nickel showed a general upward trend in 50% of the perch lakes. An increase, or indication of an increase, was seen for chromium during the last ten years. Zinc concentrations were decreasing in a majority of the perch samples and in pike from Lake Storvindeln. Arsenic concentrations were increasing in Arctic char and pike from all sites and in perch from a third of the sampling sites. Tin concentrations decreased in the majority of the perch time series during the most recent ten years. No general trend was observed for copper, silver, aluminum, bismuth, and cadmium. In general, downward trends were seen for; PCBs, HCHs, DDT, DDE and PCDD/Fs in all species (with a few exceptions). The chlorinated compounds generally showed a somewhat higher concentration in the southern parts of Sweden. Most chlorinated compounds were below the suggested target levels. No general trend was seen during the monitoring period for PBDEs. Concentrations of PBDEs in Lake Bolmen increased from the 60s and peaked in 1992/1993 and have subsequently decreased. The concentration of HBCDD was under LOQ in a majority of the samples. Several of the perfluorinated carboxylic compounds showed an increase in concentration in arctic char, while PFOS and FOSA decreased. In perch PFOS has decreased since 1995. Higher concentrations of perfluorinated compounds can in general be seen in the southern part of Sweden. In all lakes, PFOS is below the target level for all species.