Helcom : Lead concentrations in fish liver

Lead 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

Lead 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 (2008-2010 in ng/g dry weight) of lead in herring liver. The highest concentration (around 423 ng/g ) was found in the Gulf of Riga, the lowest (around 20 ng/g) in the Bothnian Bay (Harufjärden).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

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 references

Lead 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.

Assessment

The investigated time series in herring liver show significant decreasing trends at Harufjärden (-5.9%), Ängskärsklubb (autumn, -4.5%), Landsort (-5.7%), and Utlängan (autumn, -2.8%).

Lead concentrations in cod liver (after adjusting for varying fat content) showed decreasing trends from SE Gotland (-5.3%) and Fladen (about –2.8%).

Perch liver from the coastal sites Holmöarna (Bothnian Sea) and Kvädöfjärden (Baltic Proper) show decreasing concentrations of lead at an annual rate of -8.9% and -7.1% respectively.

Figure 2. Temporal trends of lead concentration (ug/g dry weight) in herring liver from four different sampling sites in the Baltic Sea (1981-2010). Harufjärden (Bothnian Bay), Ängskärsklubb (S. Bothnian Sea), Landsort (N. Baltic Proper), Utlängan (S. Baltic Proper). The linear red lines (p<0.05) and dashed light blue lines (0.05<p<0.15) presented in the figures are based on a log-linear regression analyses and the red lines show decreasing trends of about 3-6% per year for the whole time period. Decreasing trends for the last ten years are indicated at a majority of the sites. The non-linear red line (p<0.05) and the dashed blue 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 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 (1981-2010) from southern Baltic Proper (SE Gotland) and from Kattegatt (Fladen). The red linear lines presented in the figures are based on a log-linear regression analysis and show decreasing trends of -5.3 and -2.8% per year respectively and the red non-linear 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.

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

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 1981-2010 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.

Matrix	age	n analyses	n yrs	year	trend (95% ci)	mean concentration of last year (95% ci)
Herring liver
Harufjärden	3-5	439	28	81-10	-5.9 (-9.0, -2.8)*	.029 (.017-.048)
Ängskärsklubb	3-5	441	28	81-10	-4.5 (-5.8, -3.2)*	.050 (.040-.0622)
Landsort	3-5	445	30	81-10	-5.7 (-6.8,-4.6)*	.045 (.038-.055)
Utlängan	2-4	432	29	81-10	-2.8 (-4.0, -1.6)*	.085 (.069-.10)
Cod liver
SE Gotland	3-4	402	29	81-10	-5.3 (-6.6,-4.0)*	.007 (.005-.008)
Fladen	2-4	470	31	81-10	-2.8 (-4.8, .87*	.016 (.011-.022)
Perch liver
Holmöarna	3-7	150	15	95-10	-8.9(-15,-2.9)*	.008 (.004-.013)
Kvädöfjärden	3-7	135	15	95-10	-7.1(-12,-2.1)*	.010 (.007-.016)

* significant trend, p < 0.05.

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 used, see Bignert et al. 2012. Lead 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 number of years required to detect an annual change of 10 % with a power of 80% varied between 10 to 18 years for the herring time-series.

The number of years required to detect an annual change of 10 % with a power of 80% were 11 and 14 years for the cod 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 Sheet(s) 2012. Online. [Date Viewed], http://www.helcom.fi/environment2/ifs/en_GB/cover/.

Last updated: 2.11.2012