Technetium-99 in the Irish marine environment

Technetium-99 activity concentrations in seawater and biota from Irish coastal waters are presented. Time series measurements of 99Tc in seawater and Fucus vesiculosus from the western Irish Sea show that activity concentrations have increased in line with the increase in discharges of 99Tc from Sellafield. The peak in activity concentrations in both seawater and Fucus vesiculosus occurred in 1997 approximately two years after the peak in 99Tc discharges. The highest activity concentration recorded in Fucus vesiculosus showed a 29-fold increase over the mean concentration for the period 1988-1993. Technetium-99 activity concentrations were measured in fish, lobsters, prawns, mussels and oysters landed at major fishing ports on the east and northeast coasts of Ireland between 1996 and 1998. Concentration factors for 99Tc in the brown seaweed Fucus vesiculosus and certain species of fish, crustaceans and molluscs from the Irish Sea were estimated. In general, these concentration factors were higher than those in the literature which were derived from laboratory studies, but agreed well with values which were based on field studies. The mean committed effective doses to Irish typical and heavy seafood consumers due to 99Tc in the period 1996-1998 were 0.061 and 0.24 microSv, respectively.