We are exposed
to radiation from the sun and outer space, also from the naturally occurring
radioactive materials present in the earth, the house we live in, the buildings
where we work, the food and drink we consume.
Where we live in
The
houses are made up of materials which contain radioactivity. Gamma radiation
from walls, floor & ceiling, and Radon and Thoron progeny are major sources
of radiation exposure. Especially in closed rooms, Radon is the significant
dose contributing factor.
Natural Radioactivity (Bq.Kg-1) in Building Materials used
in India
|
Material
|
Type
of Radioactive isotope
|
|
K-40
|
Ra-226
|
Th-232
|
|
Cement
|
5-385
|
16-377
|
8-78
|
|
Brick
|
130-1390
|
21-48
|
26-126
|
|
Stone
|
48-1479
|
6-155
|
5-412
|
|
Sand
|
5-1074
|
1-5047
|
4-2971
|
|
Granite
|
76-1380
|
4-98
|
103-240
|
|
Clay
|
6-477
|
7-1621
|
4-311
|
|
Fly
Ash
|
6-522
|
7-670
|
30-159
|
|
Lime
stone
|
6-518
|
1-26
|
1-33
|
|
Gypsum
|
70-807
|
7-807
|
1-152
|
We are always in natural background radiation*
Cosmic-from the sun and outer space – 0.4mSv.Yr-1
Terrestrial – from the earth’s crust – 0.5mSv.yr-1
Radon – from decay of Uranium/radium – 1.2mSv.yr-1
Internal sources in the body(eg: 40K)
--- 0.3mSv.yr-1
Total Dose from
Natural Sources: ----2.4 mSv.Yr-1
What we drink
Radioactivity in
milk is over 200 times more than in
drinking water and 3 times that in beer.
From a cup of milk ,
180 beta particles of Ptassium-40 are emitted per minute
From a cup of tea, 91
beta particles of Potassium-40 are emittd per minute from tea leaves(excluding
milk and water)
What we eat
|
Food
stuff
|
K-40
(Bq.Kg-1)
|
|
Rice
|
40-90
|
|
Leafy vegetables
|
80-220
|
|
Brinjal
|
90-140
|
|
Carrot
|
60-120
|
|
Beetroot
|
90-120
|
Radiation Doses from Cosmic Rays
|
Distance
above Ground
|
Dose
Rate in µSv. h-1
|
|
~ 15 Km above ground
|
10
|
|
~ 10 Km above ground
|
5
|
|
~ 8 Km above ground
|
2
|
|
~ 2 Km above ground
|
0.1
|
|
Sea Level
|
0.03
|
Courtesy: Radiation Safety, IAEA (1996), NRPB, UK
