Lead concentrations in fish liver
Key messageLead is showing significant declining trends in almost all investigated biotic matrices of sufficient length, obviously as a result of measures taken to reduce discharges of lead to the environment.
Figure 1. Spatial variation in arithmetic mean concentration (2007-2009 in ng/g dry weight) of lead in herring liver. The highest concentration (around 493 ng/g ) was found in the Gulf of Riga, the lowest (around 20 ng/g) in the Bothnian Bay (Harufjärden). Some of the sampling sites have only been analysed for two years this far (2008-2009). 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
Lead 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 referencesLead is one of the mandatory contaminants that should be analysed and reported within both the OSPARCOM and HELCOM conventions. The North Sea Conference (1984, 1987, 1990) that covers all routes of pollution to the North Sea, states that the lead 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 lead to air and water by 50% by 1995 with 1987 as a base year.
The investigated timeseries in herring liver show significant decreasing trends at Harufjärden (-5.3%) Ängskärsklubb (autumn, -4.1%), Landsort (-5.3%) and Utlängan (autumn, -2.6%).
Lead concentrations in cod liver (after adjusting for varying fat content) showed decreasing trends from SE Gotland (-5.7%) and Fladen (about –3.3%).
Perch liver from the coastal sites Holmöarna (Bothnian Sea) and Kvädöfjärden (Baltic Proper) show decreasing concentrations of lead at an annual rate of -8.7% and -6.4% respectively.
Figure 2. Temporal trends of lead 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 lines presented are based on a log-linear regression analyses and show decreasing trends of about 2-5% per year, the magenta coloured line shows a decreasing trend during the last ten years at Landsort 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 represents a suspected outlier.
Figure 3. Temporal trends of lead concentration (ug/g dry weight) in cod liver (1981-2009) from 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 show decreasing trends of respectively -5.7 and -3.3% 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.ReferencesBignert, 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
Trend (in %) assessed from the annual geometric mean of concentrations of lead (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)|
|Harufjärden||3-5||427||27||81-09||-5.3(-8.5, -2.1)*||0.034 (0.020-0.057)|
|Ängskärsklubb||3-5||439||27||81-09||-4.1 (-5.5, -2.8*||0.056 (0.045-0.70)|
|Landsort||3-5||433||29||81-09||-5.3 (-6.5,-4.2)*||0.51 (0.43-0.62)|
|Utlängan||2-4||432||29||81-09||-2.6 (-3.9, -1.3*||0.90 (0.73-0.11)|
|Fladen||2-3||515||29||81-09||-5.2 (-6.9,-3.6)*||0.0370 (0.028-0.17)|
|SE Gotland||3-4||392||29||81-09||-5.7 (-7.0,-4.4)*||0.006 (0.005-0.008)|
|Fladen||2-4||460||28||81-09||-3.3 (-5.3,-12)*||0.015 (0.011-0.021)|
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. 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.
The number of years required to detect an annual change of 10 % varied between 10 to 18 years for the herring time-series with a power to detect a 10 % annual change close to 1.
The number of years required to detect an annual change of 10 % is between 10-14 years for the cod time-series with a power to detect a 10 % annual change close to 1.
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: 21.09.2011