Cadmium concentrations in fish liver

	Authors: Anders Bignert and Elisabeth Nyberg Swedish Museum of Natural History

Key message

Cadmium concentrations in herring are showing significant increasing trends followed by decreasing trends in several of the investigated biotic matrices of sufficient length. In general the recent levels are not significantly lower compared to the concentrations measured at the beginning of the 80-ies, despite measures taken to reduce discharges of cadmium to the environment.

Results and assessments

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. 

Figure 1. Spatial variation in concentration (dry w.) of cadmium in herring liver (2004). The highest concentration (1.9 ng/g) was found in the southern Baltic Proper, the lowest (0.33 ng/g) in the Skagerrack.

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 stabilisor 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 concentrations in herring liver from Ängskärsklubb in the Bothnian Sea and Utlängan in the Baltic proper show significant increasing log-linear trends from the start of time-series. The total increase in cadmium concentration during 1981-95 at Ängskärsklubb, Landsort and Utlängan is about 2.5 times. During recent years the increases have turned to a decrease at these sites.

Figure 2. Temporal trends of cadmium concentration (ug/g dry w.) in herring liver.

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

Figure 3. Temporal trends of cadmium concentration (ug/g dry w.) in cod liver.

The number of years required to detect an annual change of 5% varied between 10 to 19 years for the herring timeseries with a power to detect a 5% annual change ranging from 0.21 to 1.0. (Since it is not appropriate to fit a log-linear trend at Ängskärsklubb and Utlängan, these sites were excluded from the power calculations.)

References

Bignert, A., Asplund L., Willander A. 2005. Comments Concerning the National Swedish Contaminant Monitoring Programme in Marine Biota. Report to the Swedish Environmental Protection Agency, 2005-05-09. 115 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

Estimated geometric concentrations of cadmium (ug/g dry weight) for the last sampled year in various matrices and sites during the investigated time period. The age interval for fish, and the length interval for blue mussels are also presented together with the total number of analyses and the number of years of the various time-series.

* significant trend, p < 0.05, ** mean is reported if no trend is found. 

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 Contaminant Research Group at the Swedish Museum of Natural History, Stockholm. Chemical Analysis is carried out at the Centre for Environmental Monitoring at the University of Agriculture, Uppsala.

Geographical coverage: see data table and map.

Temporal coverage: see data table and figures.

Methodology and frequency of data collection, see Bignert et al, 2005

Methodology of data manipulation. For a detailed description of statistical methods use, see Bignert et al. 2004. Lead concentration 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 5% varied between 16 to 17 years.

Last updated 25 Nov 2005.