29. BIOLOGICAL EFFECTS OF RADIATION
Fiestaware: (from TPT1995:18-22) Homer Laughline China Company of Newell
WV in 1936, in five colors, including "Fiesta red," the glaze
was 14% by weight uranium oxide U3O8 (0.7% U-235) from 1936 to 1943
(when it was discontinued because the gov't) and then 0.2% (depleted)
U-235 from 1959 to 1972.
Lantern mantles: 300 mg of Th-232, corresponding to 1.2 kBq (33 nCi) per
mantle
Salt substitues (e.g. NoSalt) contain lots of potassium, including Potassium-40,
halflife 1.277 Ga. There is c. 140g of K in 70-kg adult, meaning 0.016g
of K-40, or 4.4 kBq (0.12 ?Ci). Annual dose, therefore, of 190 ?Sv (19
mrem), mostly beta radiation.
How to quantify radiation:
Activity. The becquerel (Bq) = one disintegration/second. The curie is
an old unit for radiation, equal to the activity of 1.02g of radium-226,
or 3.7x1010Bq.
Absorbed Dose. The biological effects of radiation depends on the amount
of energy deposited in the body, how fast that deposition takes place (use
punch analogy, or photoelectric effect), and the form. 1 Gray (Gy) = 1
J/kg (of body mass) = 100 rad (radiation absorbed dose) = #particles hitting
body x energy per particle / body mass.
Dose equivalent. Unit: 1 sievert = 1J/kg = 100 rem (radiation equivalent
man). Dose equivalent = Quality factor x Absorbed Dose.
In a single dose, 20 rems would have no immediately noticable (somatic)
effect. Four hundred rems is fatal.
Type of radiation Quality Factor
X- and ?-rays, ?- 1.0
Thermal neutrons 3.0
Fast neutrons or protons 10
?- and heavier particles 20
Different organs have different sensitivity to radiation, so there is another
factor, Wt, to give an Effective Dose Equivalent.
EM radiation: effect depends on the frequency i.e. the energy of the photons,
not the intensity. The little UV in sunlight causes reddening in 20 minutes,
but if the UV is filtered out (by glass, for instance) will never get a tan.
Alpha radiation (Helium nuclei): sharply defined energy
Beta radiation (electrons): emitted with an anti-neutrino (which has no biological
effect) so the electrons have a broad distribution of energies. Average is about
1/3 of the max quoted.
Neutrons
The International Commision on Radiological Protection (ICRP) sets limits on
radiation exposure based on (1) the effects of radiation on the outlying populations
at Hiroshima and Nagasaki, and (2) an acceptable level of 100 fatalities per
year per million workers. For workers at nuclear reactors, x-ray technicians,
etc, whole-body exposure limit is thus set at 50 mSv/yr. For the general populace,
1 mSv/year is the stated limit.
Common exposures to the general public: Natural background 3.5 mSy (350 mrem)
annually (2.9 mSv from Radon and progeny, plus 0.6 mSv from all other sources
combined). Five hour transcontinental flight 0.01 mSv (1 mrem); Average chest
or dental X-ray, 0.1 mSv (10 mrem) to bone marrow.
Effects: can effect the individual exposed (somatic) or that individual’s
descendents (hereditary).
Stochastic effects: where the probability of the effect, rather than its severity,
is proportional to the dose. Typically, this refers to cancer that may occurs
years or decades after exposure, making a direct causal connection difficult
to prove.
Non-stochastic effects: where the severity of the effect is in proportion to
the dose. Such effects are skin reddening, cataracts, cell depletion in bone
marrow, impaired fertility of eggs/sperm.
Japan data: 12.5 excess delayed cancers/million workers/year/mSy, and 2.5 excess
genetic defects within 2 generations.
In recent years there has been a growing concern within the healt-care community
and the general public about the dangers of radon gas accumulating in buildings.
Radon is part of the decay chain of U-238, which has a half-life of 4.4 Ga):
???
The concentration of Radon is therefore dependent on the quantities of uranium
present in the local soil and, in the case of buildings, how porous the building's
basement is to gas seeping in from the surrounding soil. Most soil contains 1
to 3 ppm uranium, but in some areas may reach 100 ppm and beyond. Sandy and gravely
soily allow the radon to diffuse (seep) more rapidly than clay-rich soils. Water
in the soil also hinders the gas diffusion.
HOUSEHOLD DETECTORS USGS RADON POTENTIAL MAP
Calculate your Personal Radiation Dose
We live in a radioactive world. Radiation is all around us as part of our natural
environment. The annual average does per person from all sources is about 360
mrems, but it is not uncommon for any of us to receive far more that that in
a given year (usually due to medical procedures). For those who work with nuclear
materials the international standards allow up to 5,000 mrems per year exposure.
Fill in the answers below based on your activities during the past year.
WHERE YOU LIVE
Cosmic radiation at sea level (from space)
For your elevation (in feet): add 3 mrem for every 1000 feet
Terrestrial (from the ground)
If you live in a state that borders the Gulf or Atlantic, add 23
If you live in the Colorado Plateau Area, add 90
If you live in Middle America or the Far West, add 46
House construction:
If you live in a stone, brick, or concrete building, add 7
WHAT YOU EAT AND DRINK
Internal radiation (in your body)
From food and water (U.S. average)
From radon (U.S. average)
40 40
200
HOW YOU LIVE
Transport of radioactive material
Low-level radioactive waste burial sites
Consumer products and sources such as radon from water and radiation
from tobacco smoke
Weapons test fallout (less than 1)
Jet plane travel: for each 1000 miles, add 1
If you have porcelain crowns or false teeth, add 0.07
If you use gas lantern mantles when camping, add 0.003
If you wear a luminous wristwatch (LCD), add 0.06
Luggage x-ray machine at an airport, add 0.002 per trip
If you use a video display terminal (less than 1), add 1
TV viewing: for each hour per day, add 0.15
If you have a smoke detector, add 0.008
If you wear a plutonium-powered cardiac pacemaker, add 100
If you had medical exposures:
Chest x-rays, add 10 per visit
Gastrointestinal tract x-ray, add 200 per visit
Dental x-rays, add 10 per visit
Nuclear medical procedures (U.S. average), add 14
If you live within 50 miles of a nuclear power plant, nuclear laboratory, or
university with a nuclear reactor, add 0.0009
If you live within 50 miles of a coal-fired power plant, add 0.03
If you smoke, add 1300
Add the scores to get your total TOTAL
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