R01011: Measurement of iodine-129 (129I) in fruit.

Study Duration: February 2002 to October 2004.

Contractor: Westlakes Scientific Consulting Limited

There is a large discrepancy between model predictions and actual measurements of ¹²⁹I in fruit from aerial discharges from Sellafield. This is mainly due to the lack of data on the transfer of ¹²⁹I to fruit. This project will improve our understanding in this area.

Iodine released into the atmosphere can exist in several chemical forms that have different transfer factors into foods. As a result, measured concentrations of ¹²⁹I often differ from predictions. Various approaches to measuring iodine were tested during the course of studies undertaken over the period 1993 to 1998. Environmental concentrations were measured using radiochemical neutron activation analysis for filter material from atmospheric samplers and environmental materials (vegetation, milk and soils). Further work is being undertaken to investigate the transfer to fruit using mass spectroscopy to measure concentrations in fruit.

The aim of this project was to determine the dominant route of uptake of ¹²⁹I (iodine-129) into fruit using accelerator mass spectrometry (AMS). This technique measures isotopes in a sample based on their mass/charge ratio. Previous modelling studies had highlighted the lack of good field data to enable more realistic predictions of how ¹²⁹I enters the terrestrial foodchain, particularly in fruit. Before this project, cautious values were used in modelling studies. These predicted values that were much higher than the few values that had been measured in the field.

This project was designed to find out if the uptake of ¹²⁹I into fruit from the discharge of gaseous radioactive iodine was from direct deposition of ¹²⁹I onto the fruit plant (leaves, stem, fruit buds), or from deposition onto the soil and uptake into fruit via the roots of the plant.

The project was set up in two phases with the successful completion of stage 1 before going to stage 2.

• to demonstrate the capability to analyse for ¹²⁹I by reporting ¹²⁹I concentrations and ¹²⁹I/¹²⁷I ratios in a series of three analytical standards
• on successful completion of the analysis of the standards, to analyse a batch of 50 fruit samples for ¹²⁹I

Unfortunately, analytical problems in trying to extract iodine isotopes from standard solutions were not resolved. As a result, it was not possible to move onto stage 2 and so no fruit samples were sent for AMS analysis.

Until these problems are resolved, there is an archive of fruit samples (frozen) stored at Westlakes Scientific Consulting Ltd. These samples are awaiting the identification of a suitable facility to analyse these samples for ¹²⁹I.

Although no key results on the activity concentrations of ¹²⁹I have been obtained, one of the positive outcomes of this work is that we have acquired a much better understanding of some of the problems inherent within the analysis of ¹²⁹I in fruit samples.

The final report is available from the Agency's Information Centre. To obtain a copy, please contact the Enquiry Desk, Information Services, Food Standards Agency (tel: 020 7276 8181/8182 or email: infocentre@foodstandards.gsi.gov.uk)

Contact: For any enquiries concerning this research project, please contact the relevant programme contact or email: science@foodstandards.gsi.gov.uk