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.
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 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.
At Harufjärden (-5.0%), Ängskärsklubb (autumn, -4.6%) and Landsort (-4.6%), the investigated timeseries in herring liver show significant decreasing trends.
Figure 1. Spatial variation in concentration (d.w.) of lead in herring liver (2002). The highest concentration (201 ng/g) was found in the southern Baltic Proper, the lowest (61 ng/g) in the Skagerrack
Lead concentrations in cod liver (after adjusting for varying fat content) showed decreasing trends from SE Gotland (-7%) and Fladen (about –4.9%).
Figure 2. Temporal trends of cadmium concentration (ug/g dry) in herring liver.
At the coastal sites Holmöarna (Bothnian Sea) and Kvädöfjärden (Baltic Proper) perch liver is sampled. Lead concentrations showed decreasing trends: -7% and –13%, respectively.
Figure 3. Temporal trends of cadmium concentration (ug/g dry) in cod liver.
Bignert, A., Asplund L. and Willander A. 2003. Comments Concerning the National Swedish Contaminant Monitoring Programme in Marine Biota. Rapport till Naturvårdsverket, 2004-04-30. 135 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
Estimated geometric concentrations of lead (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
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, 2004
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.
The number of years required to detect an annual change of 5% varied between 16 to 20 years for the herring time-series with a power to detect a 5% annual change ranging from 0.94 to 1.0. An annual change greater than 10% would likely be detected.
The number of years required to detect an annual change of 5% varied between 20 to 21 years for the cod time-series with a power to detect a 5% annual change ranging from 0.89 to 0.92. An annual change greater than 15% would likely be detected.