TCDD-equivalents in herring muscle and guillemot egg 

	Authors: Anders Bignert, Sara Danielsson, Elisabeth Nyberg Department of Contaminant Research, Swedish Museum of Natural History

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 decreasing trend could only be found in one of the herring time series in which the monitoring period is over 30 years. Thus the herring data coincides with the results for guillemot eggs during the last 15 years.

The concentrations of TCDD-equivalents are on average higher in the Bothnian Bay and Bothnian Sea compared to the Baltic Proper and the Swedish west coast.

Figure 1.  Spatial variation in mean concentration (of the annual mean values from 2006-2008 in pg/g lipid weight) of TCDD-equivalents in herring muscle. The highest concentration (around 61 pg/g) was found in the southern Bothnian Bay (Gaviksfjärden), the lowest (around 5.4  pg/g) in Skagerrakk (Väderöarna). Some of the sampling sites have only been analysed one/two years this far (among them Gaviksfjärden). Data originates from the Swedish national monitoring programme and are analysed at the Department of Chemistry, University of Umeå

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 bioavailable 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% was 12 years for the guillemot egg time series.

Only one decreasing trend could be observed in herring muscle from the Baltic and the Swedish west coast. The number of years required to detect an annual change of 5% varied between 15-23 years for the herring time series. The highest concentration (2006-2008) in herring muscle (around 61 pg/g lipid weight) was found in the southern Bothnian Bay (Gaviksfjärden), the lowest (around 5.4  pg/g lipid weight) in Skagerrakk (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 four different sampling sites (1979/90-2007/08). Harufjärden (Bothnian Bay), Ängskärsklubb (S. Bothnian Sea), Utlängan (S. Baltic Proper), Fladen (Kattegatt). The red line presented in one of the figures is based on a log-linear regression and shows a decreasing trend of about 6% per year. The horizontal dotted line is the mean concentration over the whole period. A red cross represents a suspected outlier.

Figure 3. Temporal trends of TCDD-equivalent concentration (ng/g lipid weight) in guillemot egg (1969-2008) from St. Karlsö (S. Baltic Proper). The red line presented in the figure is based on a log-linear regression analysis and shows a decreasing trend of about 3 % per year and the blue line is a simple 3-point running mean smoother fitted to the annual geometric mean values. The horizontal dotted line is the mean concentration over the whole period. A red cross represents a suspected outlier.

References

Bignert, A., Danielsson S.,  Nyberg E., Asplund L., Eriksson U., Wilander A. Haglund P. 2010. Comments Concerning the National Swedish Contaminant Monitoring Programme in Marine Biota. Report to the Swedish Environmental Protection Agency, 2010. 155 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 (2007/08). The trend is reported, if p<0.1. The total number of analyses and the number of years are also presented. The numbers presented in brackets are the 95% confidence intervals.

Metadata

Technical information

Data source: The National Swedish Monitoring Programme 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 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, 2010.

Methodology of data manipulation. For a detailed description of statistical methods use, see Bignert et al. 2010.

Quality information

The number of years required to detect an annual change of 5% with a power of 80% varied between 15 to 23 years for the herring time-series. The number of years required to detect an annual change of 5% was 12 years for the guillemot egg time-series.

For reference purposes, please cite this Baltic Sea Environment Fact Sheets as follows:

[Author’s name(s)], [Year]. [Baltic Sea Environment Fact Sheets title]. HELCOM Baltic Sea Environment Fact Sheets 2010. Online. [Date Viewed], http://www.helcom.fi/environment2/ifs/en_GB/cover/.

Last updated: 30 September 2010