Cadmium concentrations in fish liver
Key messageCadmium 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 80-ies, despite measures taken to reduce discharges of cadmium to the environment.
Figure 1. Spatial variation in arithmetic mean concentration (2007-2009 in ug/g dry weight) of cadmium in herring liver. The highest concentration (around 4.2 ug/g ) was found in the northern Bothnian Sea (Gaviksfjärden), the lowest (around 0.26 ug/g) in close to Tallinn in the Gulf of Finland. Some of the sampling sites have only been analysed for two years this far. The Swedish data originates from the Swedish national monitoring programme and are analysed at the Department of Applied Environmental Science, University of Stockholm. Additional data is obtained from ICES database.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.
Policy relevance and policy referencesThe 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.
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. Since the peak in the mid 90-ties the increases have turned to a decrease at these sites.
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 (1981-2009). Harufjärden (Bothnian Bay), Ängskärsklubb (S. Bothnian Sea), Landsort (N. Baltic Proper), Utlängan (S. Baltic Proper). The red line presented is based on a log-linear regression analyses and shows an increasing trend of about 1% per year at Utlängan, the magenta coloured line a decreasing trend during the last ten years and the blue line is a simple 3-point running mean smoother 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 w.) in cod liver (1981-2009) from the southern Baltic Proper (SE Gotland) and from Kattegatt (Fladen). The red lines presented in the figures are based on a log-linear regression analysis and shows decreasing trends of respectively -6.0 and -2.2% per year and the blue line is a simple 3-point running mean smoother 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.
Bignert, A., Berger, U., Boalt, E., Borg, H., Danielsson S., Eriksson, U., Haglund, P., Hedman, J., Holm, K., Johansson, A-K., Miller, A., Nyberg, E., Nylund, K..2011. Comments Concerning the National Swedish Contaminant Monitoring Programme in Marine Biota. Report to the Swedish Environmental Protection Agency, 2011. 224 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
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 1981-2009 and the estimated mean concentration for the last year (2009). 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.
|Matrix||age||n analyses||n yrs||year||trend (95% ci)||mean concentration of last year (95% ci)|
|Utlängan||3-4||432||29||81-09||1.4 (.32, 2.8)*||1.4 (1.1-1.9)|
|SE Gotland||3-4||353||25||81-06||-6.0 (-7.8,-4.2)*||0.013 (0.010-0.017)|
|Fladen||2-4||465||29||81-09||-2.2 (-4.6,.26)||0.066 (0.044-0.098)|
|* significant trend, p < 0.05.|
Technical informationData 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 muscle 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, 2011
Methodology of data manipulation. For a detailed description of statistical methods use, see Bignert et al. 2011. 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 informationThe 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 % 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 Sheets 2011. Online. [Date Viewed], http://www.helcom.fi/environment2/ifs/en_GB/cover/.
Last updated: 21 September 2011