Artificial radioactivity in the Irish Sea continues to stem mainly from the Sellafield nuclear plant in England, the RPII concludes. The institute stresses that "any contamination of the marine environment due to an installation from which Ireland derives no benefit remains highly objectionable from an Irish viewpoint".
RPII deputy chief executive John Cunningham picked out discharges by Sellafield of the radioisotope technetium-99 for particular criticism. Emissions began in 1994 and peaked at nearly 200 tera-becquerels (TBq) in 1995 before falling to under 100TBq in 1997. The effects on the Irish Sea "are not acceptable," Mr Cunningham said, "and the discharges should be substantially reduced and eliminated" in line with this summer's international Ospar agreement (ENDS Daily 23 July).
The RPII's monitoring shows that the overall reduction in artificial radioactivity levels in seawater and organisms is being slowed by the growth in technetium 99 activity. Mean activity levels in seawater rose from 28 mega-becquerels per litre (mBq/l) to 40 mBq/l from 1996 to 1997, while activity levels in seaweed at one site on the east coast rose from 2955 Bq/kg to 4976 Bq/kg over the same period.
Though emissions from Sellafield are clearly still a cause for concern to the Irish authorities, the RPII study shows that the radiation risk to the Irish population is extremely small.
For a typical Irish seafood consumer, it concludes, the radiation dose from artificial radioactivity in the Irish Sea was 0.32 micro-sieverts (uSv) in 1997, while a heavy seafood consumer would have been exposed to 1.43uSv. Similar heavy consumers would have received about 150uSv from naturally-occurring polonium-210 in seafood, the RPII says.
Even for heavy consumers, it notes, a dose of 1.43uSv is 0.2% of the internationally accepted annual dose limit of 1,000uSv, which itself is a third of the approximately 3,000uSv received by members of the Irish public, mainly from naturally occurring radiation.
In terms of cancer risk, Irish Sea radioactivity poses a one in 60m risk of radiation induced cancer for typical seafood consumers and one in 13m for heavy consumers, the RPII calculates. It compares this with the general risk of death from cancer of one in 479 and from road accidents of one in 9,232.
RPII, tel: +353 1 269 7766.
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