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Environmental thoron (220Rn) : A review
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T.V. Ramachandran   |
| , tvrradon@gmail.com |
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Abstract: (18262 Views) |
| Ever since studies on uranium miners established
the presence of a positive risk coefficient for
the occurrence of lung cancer in miners exposed to
elevated levels of 222Rn and its progeny, there was a
great upsurge of interest in the measurement of
222Rn in the environment and considerable data is
generated on the levels of 222Rn in the environment
across the worlds and is periodically reported by UNSCEAR.
In contrast to this, data pertaining to 220Rn in
indoors and workplace environment is scare due to
the general perception that its levels are negligible
due to its shorter half life, and subsequently its contribution
to the total inhalation dose is ignored, in the
presence of other significant sources of natural
radiation. Many locations have higher levels of
natural background radiation due to elevated levels
of primordial radio-nuclides in the soil and their decay
products like radon (222Rn), and thoron (220Rn) in the
environment. It is estimated inhalation of 222Rn, 220Rn
and their short lived progenies contribute more than
54 % of the total natural background radiation dose
received by the general population. This component
is not adequately estimated for any country so far on
a national level. 220Rn problem will also be a problem
in industries which uses thorium nitrate. Including
India, lamps using throated gas mantles are being
still used for indoor and outdoor lighting and hawkers
in rural as well as urban areas. Considering the fact
that large amount of thorium nitrate is being handled
by these industries, contribution to the inhalation
dose of workers from 220Rn gas emanated and build
up of the progeny in ambient air may also be quite
significant. In this article current status of 220Rn
levels in the indoor environment and workplaces as
well as in other industries where large amount of
232Th is being handled, is being summarized. Iran. J.
Radiat. Res., 2010 8 (3): 129-147 |
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| Keywords: Background radiation, radon, thoron, inhalation dose. |
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Full-Text [PDF 313 kb]
(6103 Downloads)
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Type of Study: Short Report |
Subject:
Radiation Biology
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