TCDD-equivalents in herring muscle and guillemot egg 
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Key message
The concentrations of TCDD-equivalents in guillemot eggs show an overall significant decreasing trend. However, the concentrations of TCDD-equivalents have not continued to decrease significantly during the recent 15 years. A significant increasing trend can be seen in the Bothnian Bay for TCDD-equivalents in herring muscle from 1990-2007. No significant changes can be found in Kattegatt and the southern Baltic Proper for the same time period, which coincides with the results for guillemot eggs during this time period.
The concentrations of TCDD-equivalents are higher in the Bothnian Bay and Baltic Proper compared to Kattegat.
Figure 1. Spatial variation in mean concentration (of the annual mean values from 2004-2007 in pg/g lipid weight) of TCDD-equivalents in herring muscle. The highest concentration (around 58 pg/g) was found in the northern Bothnian Sea (Gaviksfjärden), the lowest (around 7.6 pg/g) on the Swedish west coast (Väderöarna). Data originates from the Swedish national monitoring programme. Some of the sampling sites have only been analysed once this far (2007, including both Gaviksfjärden and Väderöarna) and the between year variation is therefore unknown.
Results and assessments:
Relevance of the indicator for describing developments in the environment
Analyses of contaminants in biotic samples, in contrast to abiotic matrices, exhibit the bioavaillable part of the contaminants. The lipid content of both herring muscle tissue and guillemot eggs is high, about 2-4% and 11-13% respectively, and thus appropriate for analysis of fat-soluble contaminants as dioxins. Herring are also commonly used for human consumption.
Policy relevance and policy references
Dioxins are comprised by the objective of HELCOM’s strategy for hazardous substances, that is to continuously reduce discharges, emissions and losses of hazardous substances, with a goal of their eventual cessation by the year 2020. The ultimate aim is to achieve concentrations in the environment near background values for naturally occurring substances and close to zero for man-made synthetic substances. This objective was adopted in 1998 and dioxin has been selected as one of the priority substances for immediate action.
Dioxins are also included in The Stockholm Convention on Persistent Organic Pollutants (POPs), an international agreement, requiring measures for reducing or preventing releases of dangerous substances to the environment.
Assessment
Significant decreasing trends are observed for TCDD-equivalents in guillemot eggs. However, the concentrations of TCDD-equivalents have not continued to decrease significantly during the recent 15 years. The number of years required to detect an annual change of 5% varied between 12 and 18 years for the last ten years in guillemot.
A significant increasing trend can be seen in herring muscle from the Bothnian Bay, but not from the other two sites. The number of years required to detect an annual change of 5% varied between 16-19 years for the herring time series. The highest concentration in herring (around 58 pg/g) was found in the northern Bothnian Sea, lowest (around 7.6 pg/g) on the Swedish west coast (Väderöarna).
TCDD-equivalents show declining trends on most localities due to measures taken to reduce emissions between 1969 and 1985 but after that, this decline has ceased, contrary to e.g. PCBs.
Figure 2. Temporal trends of TCDD-equivalent concentration (pg/g lipid weight) in herring muscle from three different sampling sites (1990-2007). Harufjärden (Bothnian Bay), Utlängan (S. Baltic Proper), Fladen (Kattegatt). The red line presented in the figure is based on a log-linear regression analysis and shows an increasing trend of 4.1% per year. The horizontal dotted line is the mean concentration over the whole period.
Figure 3. Temporal trends of TCDD-equivalent concentration (ng/g lipid weight) in guillemot egg (1969-2007) from St. Karlsö. The red line show a significant decreasing trend of 3.0% per year and the blue line is a simple 3-point running mean smoother fitted to the annual geometric mean values
References
Bignert, A., Danielsson S., Strandmark A., Nyberg E., Asplund L., Eriksson U., Wilander A. Haglund P. 2008. Comments Concerning the National Swedish Contaminant Monitoring Programme in Marine Biota. Report to the Swedish Environmental Protection Agency, 2008. 128 pp.
Data
Trend (in %) assessed from the geometric mean of concentrations of TCDD-eqv. (pg (herring) ng (guillemot egg)/g lipid weight) and the estimated mean concentration for the last year (2007). The trend is reported, if p<0.1 and the numbers presented in brackets are the 95% confidence intervals. The total number of analyses and the number of years of the various time-series are also presented.
Metadata
Technical information
Data source: The National Swedish Monitoring Program of Contaminants in Biota
Sampling, sample preparation, storage in specimen bank and evaluation of results are carried out by the Department of Contaminant Research at the Swedish Museum of Natural History, Stockholm. Chemical Analysis is carried out at the Department of chemistry at the University of Umeå.
Geographical coverage: see data table and map.
Temporal coverage: see data table and figures.
Methodology and frequency of data collection, see Bignert et al. 2008.
Methodology of data manipulation. For a detailed description of statistical methods use, see Bignert et al. 2008.
Quality information
The number of years required to detect an annual change of 5% with a power of 80% varied between 16 to 18 years for the herring time-series. The number of years required to detect an annual change of 5% was 14 years for the guillemot egg time-series.
For reference purposes, please cite this indicator fact sheet as follows:
[Author’s name(s)], [Year]. [Indicator Fact Sheet title]. HELCOM Indicator Fact Sheets 2009. Online. [Date Viewed], http://www.helcom.fi/environment2/ifs/en_GB/cover/.
Last updated: 22 October 2009