Overall there has been a significant reduction of hexachlorobenzene concentrations in seabird eggs during the time period from 1983 to 2003.
This reduction is apparent in herring gull, common guillemot and kittiwake and may also occur in other seabird species. The common eider had significant lower concentration of hexachlorobenzene than the other seabird species. The hexachlorobenzene concentration in the common eider was only about 1/10 of that found in other seabird species.
No regional differences were found in the data.