Radionuclides Transfer from Soil to Tea Leaves and Estimation of Committed Effective Dose to the Bangladesh Populace

Considering the probable health risks due to radioactivity input via drinking tea, the concentrations of Ra-226, Th-232,K-40 and Cs-137 radionuclides in the soil and the corresponding tea leaves of a large tea plantation were measured using high purity germanium (HPGe) gamma-ray spectrometry. Different layers of soil and fresh tea leaf samples were collected from the Udalia Tea Estate (UTE) in the Fatickchari area of Chittagong, Bangladesh. The mean concentrations (in Bq/kg) of radionuclides in the studied soil samples were found to be 34 +/- 9 to 45 +/- 3 for Ra-226, 50 +/- 13 to 63 +/- 5 for Th-232, 245 +/- 30 to 635 +/- 35 for K-40 and 3 +/- 1 to 10 +/- 1 for Cs-137, while the respective values in the corresponding tea leaf samples were 3.6 +/- 0.7 to 5.7 +/- 1.0, 2.4 +/- 0.5 to 5.8 +/- 0.9, 132 +/- 25 to 258 +/- 29 and <0.4. The mean transfer factors for Ra-226, Th-232 and K-40 from soil to tea leaves were calculated to be 0.12, 0.08 and 0.46, respectively, the complete range being 1.1 x 10(-2) to 1.0, in accordance with IAEA values. Additionally, the most popularly consumed tea brands available in the Bangladeshi market were also analyzed and, with the exception of K-40, were found to have similar concentrations to the fresh tea leaves collected from the UTE. The committed effective dose via the consumption of tea was estimated to be low in comparison with the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) reference ingestion dose limit of 290 mu Sv/y. Current indicative tea consumption of 4 g/day/person shows an insignificant radiological risk to public health, while cumulative dietary exposures may not be entirely negligible, because the UNSCEAR reference dose limit is derived from total dietary exposures. This study suggests a periodic monitoring of radiation levels in tea leaves in seeking to ensure the safety of human health.

Automated summary

Using HPGe gamma-ray spectrometry, this study analyzed the concentrations of radionuclides in soil and tea leaves from a large tea plantation in Bangladesh. The transfer factors from soil to tea leaves were found to be relatively low for Ra-226, Th-232, and K-40. The popular tea brands in the market showed similar radionuclide concentrations to the fresh tea leaves, indicating a low radiological risk from tea consumption.