Radon-222 Brain Dosimetry

Abstract

The human brain dose from radon-222 ( 222 Rn) exposure is calculated here using 222 Rn tissue solubility data. A fraction of 222 Rn inhaled dissolves in blood and cellular fluids and circulates to brain and all organs. Radon-222 has a relatively high solubility in blood and body fluids based on human inhalation experiments. The brain dose uses calculated concentrations of 222 Rn in blood and cellular fluids from exhaled breath measurements following human exposure in a 222 Rn chamber. The annual brain dose from continuous inhalation of a concentration of 100 Bq m −3 is about 450 times less than the dose to bronchial epithelium from inhalation of the same 222 Rn concentration. Based on the 222 Rn dosimetry here, it is highly unlikely that brain cancer is related to even high 222 Rn exposures. Any functional or neurodegenerative issues from exposure to very small doses of 222 Rn alpha particles are, at present, unknown.

Radon-222 and Leukemia

“…The 222 Rn solubility measurements used here were made at the USAEC Health and Safety Lab using their 222 Rn chamber for exposure and ionization chambers calibrated with 222 Rn from NBS (now NIST) standards for breath measurements (Harley et al 1994). A complete description of the solubility experiments can be found in Harley and Robbins (2022). The calculations use the measured 222 Rn blood solubility of 3 Bq in blood or 37 Bq m −3 222 Rn air concentration (Harley et al 1994).…”

“…For comparison with another organ, the 222 Rn activity in brain due to blood solubility is 3.9 Â 10 −2 Bq vs. 1.09 Â 10 −2 Bq in bone for continuous 222 Rn inhalation of 100 Bq m −3 . The higher brain activity is due to the higher blood flow rate to brain than bone (Harley and Robbins 2022). In Table 1, the activity concentration for men and women yields a lifelong daily emission of over 900 and 1,400 alpha particles in bone, respectively, each with the potential for DNA strand breaks.…”