Concentrations of ¹³⁷Cs and ⁴⁰K in Mushrooms Consumed in Japan and Radiation Dose as a Result of Their Dietary Intake

Abstract

Mushrooms are known to accumulate radiocesium. To estimate the intake of radiocesium through the eating of mushrooms, about 30 samples belonging to 4 commonly consumed species (Lentinula edodes, Hypsizigus marmoreus, Grifola frondosa, and Tricholoma matsutake), were analyzed for ¹³⁷Cs and ⁴⁰K. The concentration ranges were 0.060-29 Bq kg^-1 (wet wt) for ¹³⁷Cs and 38-300 Bq kg^-1 (wet wt) for ⁴⁰K. The geometric mean concentration for ¹³⁷Cs was 0.56 Bq kg^-1 (wet wt), and the mean concentration for ⁴⁰K was 92 Bq kg^-1 (wet wt). The ¹³⁷Cs concentrations in L. edodes cultivated in mushroom beds (sawdust-rice bran media) were lower than those cultivated on bed logs (natural wood with bark). The annual intake of ¹³⁷Cs per person through mushrooms was calculated, by using the current analytical results and food consumption data in Japan, to be 3.1 Bq for ¹³⁷Cs, which is about 28% of the total dietary intake of this nuclide. The effective dose equivalent of ¹³⁷Cs through mushrooms was estimated to be 4.0 ¤ 10^-8 Sv, which is about the half the value obtained in our previous study. The decrease of the ¹³⁷Cs intake through mushrooms is probably related to changes in cultivation methods in recent years, from the use of bed logs to mushroom beds.