Cadmium concentrations in fish liver    

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

Key message

Cadmium concentrations in herring are generally showing significant increasing trends followed by decreasing trends. In general, the recent levels are not significantly lower compared to the concentrations measured at the beginning of the 1980s, despite measures taken to reduce discharges of cadmium to the environment.

Figure 1. Spatial variation in arithmetic mean concentration (2008-2010 in ug/g dry weight) of cadmium in herring liver. The highest concentration (around 3.6 ug/g ) was found in the northern Bothnian Sea (Gaviksfjärden), the lowest (around 0.35 ug/g) in Kattegat (Fladen). The Swedish data originates from the Swedish national monitoring programme and are analysed at the Department of Applied Environmental Science, Stockholm University. Additional data is obtained from ICES database.

Relevance of the indicator for describing developments in the environment

Cadmium concentration in liver tissue from various species show coherent trends of similar magnitudes from various regions. The investigated species are commonly used for human consumption.

Policy relevance and policy references

The North Sea Conference (1984, 1987, 1990) that covers all routes of pollution to the North Sea, states that the cadmium discharges are to be reduced by 70% between 1985 and 1995, using 1985 as a base year.

The Minister Declaration from 1988, within HELCOM, calls for a reduction of the discharges of cadmium to air and water by 50% by 1995 with 1987 as a base year.

The Swedish Parliament has agreed on a general reduction of cadmium discharges aiming at a reduction of 70% between 1985 and 1995. Further, that all use of cadmium that implies a risk of discharges to the environment, in a longer term perspective, will cease (prop 1990/91:90, JoU 30, rskr.343).

In 1982, the use of cadmium in electroplating and as a thermal stabiliser was banned in Sweden.

A fee on batteries containing cadmium was introduced 1987 in Sweden. This fee was raised considerably in 1991.

The content of cadmium in fertilisers was restricted to 100g/ton phosphorus, 1993.01.01 in Sweden.

Assessment

Cadmium concentration in herring liver from Utlängan in the Baltic proper show a significant increasing log-linear trend from the start of the time-series. The total increase in cadmium concentration during 1981-95 at Ängskärsklubb, Landsort and Utlängan is about 2.5 times.

Cadmium concentrations in cod liver samples (adjusted for varying fat content) from south east of Gotland and Fladen, however, show significant decreasing trends.

Figure 2.  Temporal trends of cadmium concentration (ug/g dry weight) in herring liver from four different sampling sites in the Baltic Sea (1981-2010). Harufjärden (Bothnian Bay), Ängskärsklubb (S. Bothnian Sea), Landsort (N. Baltic Proper), Utlängan (S. Baltic Proper). The red linear line presented is based on a log-linear regression analyses and shows an increasing trend of about 1% per year at Utlängan and the red non-linear lines are simple 3-point running mean smoothers fitted to the annual geometric mean values. The horizontal line is the mean concentration of the analysed period. A red cross represent a suspected outlier.

Figure 3. Temporal trends of cadmium concentration (ug/g dry weight) in cod liver (1981-2010) from the southern Baltic Proper (SE Gotland) and from Kattegatt (Fladen). The red linear lines and dashed light blue linear line presented in the figures are based on a log-linear regression analysis. The red lines shows decreasing trends of  -4.8 and -3.0 % per year respectively (p<0.05) and the light blue line shows an increasing trend for the last ten years (0.05<p<0.15). The red non-linear line (p<0.05) and the dashed blue non-linear line (0.05<p<0.1) are simple 3-point running mean smoothers fitted to the annual geometric mean values. The horizontal line is the mean concentration over the whole period. A red cross represents a suspected outlier.

References

Bignert, A., Berger, U., Borg, H., Danielsson S., Eriksson, U., Faxneld, S., Haglund, P., Holm, K., Nyberg, E., Nylund, K. 2012. Comments Concerning the National Swedish Contaminant Monitoring Programme in Marine Biota. Report to the Swedish Environmental Protection Agency, 2012. 228 pp.

Grimås, U., Göthberg, A., Notter, M., Olsson, M., and Reutergårdh, L. 1985. Fat Amount - A Factor to Consider in Monitoring Studies of Heavy Metals in Cod Liver. Ambio VOL 14, No 3, pp 175 - 178.

Data

Table 1. Trend (in %) assessed from the annual geometric mean of concentrations of  cadmium (ug/g dry weight) in various matrices and sites during the time period 1981-2010 and the estimated mean concentration for the last year (2010). The trend is reported, if p<0.1. The age interval, 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 ICES database and results from the National Swedish Monitoring Programme of Contaminants in Biota. Data from ICES data base has been recalculated from fresh weight basis to dry weight basis. A dry weight percentage of 35 percent in herring liver has been assumed when information on dry weight content was missing in the ICES database.

For the Swedish data, 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 Applied Environmental Science at Stockholm University.

Geographical coverage: see data table and map.

Temporal coverage: see data table and figures.

Methodology and frequency of data collection, see Bignert et al, 2012

Methodology of data manipulation. For a detailed description of statistical methods use, see Bignert et al. 2012. Cadmium concentrations are adjusted for varying fat content by ANCOVA. For a comprehensive description of the relationship between heavy metal concentration and fat content in cod liver, see Grimås et al. 1985. 

Quality information

The non-linear trends found in the cadmium series makes it difficult to estimate the quality in terms of power. From the linear parts of the trends the number of years required to detect an annual change of 10% with a power of 80% varied between 11 to 15 years.

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 Sheet(s) 2012. Online. [Date Viewed], http://www.helcom.fi/environment2/ifs/en_GB/cover/.

Last updated: 2 November 2012