The environmental toxicants examined in this report can be classified into five groups –
heavy metals, chlorinated compounds, brominated flame retardants, polyaromatic
hydrocarbons and perfluorinated compounds. Each of these contaminants has been
examined from various sites for up to six different fish species, in blue mussels, and in
guillemot eggs, for varying lengths of time. The following summary examines overall
trends, spatial and temporal, for the five groups.
Condition and Fat Content
Condition and fat content in different species tended to follow the same pattern at the same
sites, with a few exceptions. Most of the fish species generally displayed a decreasing trend
in both condition and fat content at most sites examined. Exceptions to this were increases
in fat content and condition factor seen in cod liver at both sites; an increase in condition
for herring at Ängskärsklubb in spring; and in perch and eelpout, a decrease in fat content at
Kvädöfjärden (perch) and Väderöarna (eelpout) but no trend in condition for the same site.
Due to a change in methods for metal analysis (not Hg) in 2004, values between 2003 and
2007 should be interpreted with care. From 2009 metals are analyzed at ITM, Stockholm
The longer time series in guillemot egg and spring-caught herring from the southern
Bothnian Sea and southern Baltic Proper show significant decreases of mercury. The
herring site in the southern Bothnain Sea indicates a local Hg-source. The rest of the time
series show varying concentrations over the study period, and even increasing trends in e.g.
cod muscle and eelpout muscle from Väderöarna, but the concentrations are fairly low
compared to measured concentrations in perch from fresh water and coastal sites. However,
in most cases, these concentrations are above the newly suggested EU-target level of 20
ng/g wet weight.
Lead is generally decreasing over the study period (in time series of sufficient length),
supposedly due to the elimination of lead in gasoline. Elevated lead concentrations
between 2003 and 2007 (e.g. Harufjärden) should be viewed with caution (see above
regarding change in analysis methods).
Cadmium concentrations show varying non-linear trends over the monitored period. It is
worth noting that despite several measures taken to reduce discharges of cadmium,
generally the most recent concentrations are similar to concentrations measured 30 years
ago in the longer time series.
The reported nickel concentrations show no consistent decreasing trends. Some series begin
with two elevated values that exert a strong leverage effect on the regression line and may
give a false impression of decreasing trends. Chromium generally shows decreasing trends,
possibly explained by a shift in analytical method. The essential trace metals, copper and
zinc, show no consistent trends during the monitored period.
2012. , 229 p.