An Assessment of Aquatic Radiation Pathways in Northern Ireland
SR(02)14
December 2002

EXECUTIVE SUMMARY

This report describes an assessment of aquatic radiation exposure pathways in Northern Ireland, It comprises:

• a survey of consumption, occupancy and contact rates for local people
• an assessment of their radiation exposure using monitoring data

The aim of the habits survey was to obtain site specific habits survey data for use in identifying radiation exposure pathways to the local population and subsequent definition of critical groups. Rates for seafood consumption, occupancy of coastal areas, and handling of commercial fishing gear, seaweed, shellfish and sediment were obtained. Consideration was also given to potential radiation exposure through related terrestrial pathways, e.g. use of seaweed as a fertiliser on land used for food production, and unusual and novel exposure pathways, such as seaweed and wildfowl consumption, beach sand use and inadvertent ingestion of seawater and sediment.

The habits of more than 800 individuals were recorded. The data mainly related to adults though some observations for children are presented.

The adult critical groups of local seafood consumers were identified as eating:

• Fish 99 kg/y (the mean of 30 high-rate consumers),
• Crustaceans 34 kg/y (the mean of 66 high-rate consumers), .Molluscs 7.7 kg/y (the mean of 11 high-rate consumers),
• Dulse seaweed 10 kg/y (the mean of 7 high-rate consumers).

The species consumed were, rounded to the nearest 5%:

• Fish - 40% Haddock and 60% mixed fish, comprising of cod, mackerel, sole, hake, plaice, pollack, herring, whiting, turbot and halibut.
• Crustaceans - 65% Nephrops, 25% edible crab claws, 5% edible crab and 5% lobster .
• Molluscs - 75% mussels, 15%Marine plants - scallops and 10% clams
• Dulse - seaweed (Rhodymenia palmata) -100%

For coastal area occupancy, the survey identified the following adult critical groups:

• 1100 h/y over sand/mud (for a beach angler),
• 820 h/y over sand (the mean of three dog walkers and a lifeguard),
• 9.0 h/y over saltmarsh (the mean of 71 members of a local game and wildfowling conservation association).

For handling, the survey identified the following adult critical groups:

• 1500 h/y handling commercial fishing gear (the mean of 24 individuals handling crustacean pots and fishing nets),
• 100 h/y handling sand/mud (one individual commercially picking winkles), .950 h/y handling dulse seaweed (the mean of 4 individuals).

The following suggested additions or changes to the current monitoring programme are based on the findings of this survey.

1. Monitoring of haddock instead of spurdog. Haddock was the fish species most commonly consumed by members of the adult critical group. No consumption of spurdog was reported during the survey.
2. Monitoring of edible crab claws. Edible crab claws were consumed by members of the adult critical group and by many of the crustacean consumers interviewed during the survey.
3. Monitoring of clams and scallops. These molluscs were consumed by the adult critical group but are not currently sampled.
4. Given the high rates of handling of commercial fishing gear and dulse seaweed, beta dose rate monitoring of these materials could be undertaken
5. Gamma dose rate measurements over sand/mud at Greencastle. This was the location for the high occupancy rate beach angler.
6. Gamma dose rate measurements over sand/mud in Carlingford Lough where oyster baskets are tended (gamma dose rates for winkle pickers at Killough Bay are already monitored by the Environment and Heritage Service).
7. Gamma dose rate measurements over saltmarsh at Mill Bay could be considered. This was the area where wildfowling took place, though it should be noted that occupancy rates were very low.

All other sampling and in-situ measurements should remain unchanged.

For dose assessment purposes, it is considered that a conservative assessment of effective dose would be based on consumption of 99 kg/y fish, 34 kg/y crustaceans and 7.7 kg/y molluscs together with 1100 h/y occupancy over sand/mud.

The dose assessment combined the results of the habits survey with environmental monitoring data for 2000. It was found that the critical group in Northern Ireland would have received a dose of 0.018 mSv y^-1, with 0.015 mSv y^-1 due to consumption of seafood. Average rate seafood consumers would have received 0.003 mSv y^-1. These doses are well within the recommended limit for members of the public of 1 mSv y^-1.

Copies of this reports are available from the Foundation, price £25.00, less 20% to FWR members.

N.B. The report is available for download from the SNIFFER Website