Radon-222
being gaseous inert radionuclides, inhalation of the radon gas is not as
hazardous as its short-lived, alpha emitting daughter products, with different
half-lives. While inhaled radon gas is exhaled out, inhaled particulate radon
daughters get deposited in the respiratory tract and continue to give dose to
the lung tissues until they fully decay. In the meantime, some amount of the deposited
daughter products, being highly soluble in body fluids (like blood) and get transported
to different organs/tissues and finally get excreted through urine. Hence, the
inhalation dose (internal dose) received by the lung and other organs is much higher
in case of inhalation of radon daughters than the radon gas alone.
In uranium
mines, inhalation of radon daughter is a major health hazard. There is a
relation between the exposure to radon daughters and the lung cancer incidents
amongst the mine workers. Protection standards are developed based on the exposure
data.
The main strategy
to protect the workers is to use proper respiratory protection to filter out
the daughter products; provide adequate once-through ventilation in the work
areas to dilute and disperse the radon and radon daughter activity, and monitor
the activity levels in the air continuously.
The protection
standards for radon, thoron and their daughter products are discussed in more
detail in an Editorial by Dr. Pushparaja: Radon in dwellings and workplaces: An
update on current regulations, Radiation Protection and Environment Journal,
Vol. 42 (1&2), 2019, p. 1-4.
