Radiocaesium activity concentrations in the fruit-bodies of macrofungi in Great Britain and an assessment of dietary intake habits.
Radiocaesium activity concentrations in the fruit-bodies of some species of macrofungi are higher than in many other foodstuffs. The consumption of fruit-bodies contributes significantly to radiocaesium intake of humans in some countries. In the United Kingdom, the collection of wild fungi has generally been considered to be of minor importance and there are few data on consumption rates or radiocaesium activity concentrations in most edible species. Samples of commonly eaten species in Great Britain have been collected to assess radiocaesium contamination levels and geographical variation. Concurrently, surveys of consumption habits were conducted. A total of 425 samples representing 37 different species were collected. Significantly higher radiocaesium activity concentrations occurred in mycorrhizal compared to saprotrophic or parasitic species. The highest 137Cs activity concentration of 30.5 kBq kg-1 dry wt. was determined in a sample of Hydnum repandum collected in Wales. The transfer of radiocaesium from soil to fungal fruit-bodies was highly variable, ranging over three orders of magnitude within individual species. A number of approaches to quantifying radiocaesium transfer from soil to fungal fruit-bodies were used. Although these were in general agreement with previously measured values in other countries, all the approaches gave variable results. Over 200 people responded to the dietary habits questionnaire. The median intake rate was 0.75 kg year-1 (fresh wt.) and 60% of respondents consumed only one species (generally Agaricus campestris). However, intakes of up to 26 kg year-1 were recorded and a total of 82 species were consumed. The intake of 137Cs was determined by the amount of mycorrhizal fungi in the diet rather than the total intake of fungi. Assuming median recorded 137Cs activity concentrations in each fungal species, the estimated annual committed effective dose for over 95% of respondents was < 1 microSv. Hence, currently, the consumption of wild fungi in the UK would not be expected to significantly increase the dose above that attributable to the normal diet of most consumers. However, the results of this study demonstrate that, in the event of any future accidental release of radiocaesium, the potential ingestion dose received from the consumption of wild fungi would need to be considered.