¹³⁷Caesium, ⁴⁰Potassium and potassium in raw and deep-oil stir-fried mushroom meals from Yunnan in China

A number of wild, edible mushroom species (Baorangia bicolor, Boletus calopus, Boletus obsclereumbrinus, Butyriboletus roseoflavus, Rubroboletus sinicus, Rugiboletus extremiorientalis and Xerocomus sp.) were collected in 2017, from Yunnan (Yuxi prefecture) in SW China. Samples of raw and stir-fried pools of these specimens were analysed for radioisotopes 137Cs (caesium) and 40 K (potassium), and for total K concentrations. On a whole (wet) weight (ww) basis, 137Cs activity ranged from <0.10 to 0.75 Bq kg−1 for raw, and from 0.5 to 4.4 Bq kg-1 in stir-fried mushrooms. Radiopotassium (40K) activity ranged from 57 to 96 Bq kg−1 ww for raw, and 170 to 370 Bq kg−1 ww for stir-fried mushrooms, while the corresponding concentration ranges for total K were 2100–3400 mg kg−1 ww (mean: 2800 ± 3900 mg kg−1 ww), and 6000–13000 mg kg−1 ww) mean: 8700 ± 2100 mg kg−1 ww), respectively. This data indicates that mushrooms from this region show negligible 137Cs contamination with evidently higher activity levels of 40K. The deep oil stir-frying process results in enrichment in the resulting meals for all three determinants. 100 g meal portions showed 137Cs activity in the range <0.08 to 0.44 Bq 100 g−1 ww (mean 0.15 ± 0.12 Bq 100 g−1 ww), and 40K activity from 16 to 37 Bq 100 g−1 ww (mean 24 ± 6 Bq 100 g−1 ww). The consequent exposure from 40K contained in a single 100 g serving and weekly (100 g x7) servings was equivalent to radiation doses in the range of 0.099 to 0.23 µSv and 0.68–1.6 µSv per capita (means 0.15 ± 0.04 and 1.1 ± 0.3 µSv). This is equivalent to doses in the range of 0.0017 to 0.0038 µSv kg-1 bm day-1 and 0.011 to 0.027 µSv kg-1 bm week-1 respectively (mean values of 0.0025 ± 0.006 µSv kg-1 bm day-1and 0.018 ± 0.004 µSv kg-1 bm week-1). Analogically to the annual 137Cs radiation exposure resulting from high rates of annual consumption (20–24 kg per capita), the estimated annual dose of radiation from 40K would range from 0.34 up to 0.92 µSv kg-1 bm (mean 0.60 µSv kg-1 bm). Thus in practice, high annual consumption rates of wild, stir-fried mushrooms as seen in Yunnan, would result in negligible internal doses from decay of artificial 137Cs, relative to that from natural 40K. The 100 g servings also contained between 590–1300 mg K making this local food one of the top dietary sources of nutritionally important potassium for local consumers.