lochbaum on radiation

[Norman & Karen Cohen <norco@bellatlantic.net>]

Dave's two cents. Now is radiation all the same, or are there "differences"? Or our
we looking
at the same thing in two different ways?

norm

DaveL wrote:

> Hello Norm:
>
> Regarding your question about radiation, there are differences in the biological
> effects from different kinds of background radiation, differences in the
> biological effects from different kinds of man-made radiation, and therefore
> differences between biological effects of background and man-made radiation. The
> differences are due to the energy levels involved and to the pathways for
> damage. For example, Iodine-131 is primarily a man-made radiation source. It is
> a gas that can be inhaled. Inside the body, it tends to be absorbed by the
> thyroid gland where is can cause thyroid cancer. Radon is also a radioactive
> gas, but it is primarily a background or natural radiation source. When inhaled,
> it tends to cause damage to the lungs. I realize that this response is not a
> simple, clean answer to your question, but it's my best effort to do so.
>
> Here's information on radiation effects from the NRC (I don't know if the
> RadSafe folks have given this material their endorsement or not):
>
> =====
>
>     TIP:36 - Biological Effect of Radiation
>
> Background
>
> Radiation is all around us, occurring naturally in the environment. We are
> exposed all the time to radiation from radon in the air; uranium, radium and
> thorium in the earth; cosmic rays from outer space and the sun; radioactive
> potassium in our food and water; and radioactive material within our own bodies.
> This is commonly called naturally-occurring background radiation.
>
> The average radiation exposure to an individual in the United States is about
> 360 millirem (mrem) or 3.6 millisievert (mSv) per year. About 300mrem (3 mSv) of
> this is from natural sources, including radon [200 mrem(2mSv)] that emanates
> from the ground, as well as cosmic, terrestrial and internal radiation [100 mrem
> (1mSv)]. The largest man-made source is medical diagnosis, accounting for about
> 50 mrem (0.5 mSv) per year. Consumer products such as smoke detectors, exit
> signs and luminous watch dials contribute about 10 mrem (0.1 mSv) per year.
>
> Background radiation varies depending on the area where you live, the type of
> housing construction you live in, and what you eat. For instance, Colorado has
> higher radiation levels because, at its high altitude, there is more exposure to
> cosmic rays and with its naturally-occurring uranium enriched soil, there is
> more terrestrial radiation. Brick homes have higher natural radiation levels
> than homes made of other materials such as wood; domestic water supplies
> naturally contain radon; and certain foods such as bananas and Brazil nuts
> naturally contain higher levels of radiation than other foods.
>
> In addition, consumer products such as tobacco, fertilizer product and coal have
> noticeable concentrations of naturally-occurring radionuclides including
> potassium-40. Above this background level, the NRC limits maximum radiation dose
> to the public to 100 mrem per year (1 mSv/yr), and limits dose to adults working
> in nuclear operations to 5,000 mrem per year (50 mSv/yr).
>
> Discussion
>
> Biological effects of radiation on living cells may result in three outcomes:
> (1) cells repair themselves, resulting in no damage; (2) cells die, much like
> millions of body cells do every day, being replaced through normal biological
> processes; or (3) cells change their reproductive structure. The effects of
> radiation, like those of most chemical substances, can be seen clearly only at
> doses much higher than are allowed by Federal regulations.
>
> Biological effects of radiation may be classified as prompt or delayed. Prompt
> effects can appear in a matter of minutes to as long as a few weeks after
> exposure to very high doses of radiation. The higher the dose, the sooner the
> effects will appear, and the higher the probability of death. For example, in
> 1986, firefighters battling the fire at the Chernobyl nuclear power plant in the
> Ukraine died from very large doses [approximately 1,100,000 millirad (11,000
> milligray)] of radiation.
>
> Because radiation affects different people in different ways, it is not possible
> to indicate what dose is needed to be fatal. However, it is believed that 50% of
> a population would die within thirty days after receiving a dose over a period
> of a few minutes to hours of between 250,000 to 450,000 mrem (2500 to 4500 mSv).
> This would vary depending on the health of the individuals before the exposure
> and the medical care received after the exposure.
>
> It should be noted that the doses referred to above are acute whole body doses,
> meaning that the whole body is exposed to the radiation in a very short period
> of time (minutes to hours). Exposure of only parts of the body will likely lead
> to more localized effects, such as skin burns or tissue damage in the exposed
> area.
>
> Delayed effects of radiation are effects that appear many years (usually between
> 5-20 years) after exposure. The period before cancer appears is known as the
> latent period. Genetic effects and the development of cancer are the primary
> health concerns. The cancers that may develop as a result of radiation exposure
> are indistinguishable from those that develop spontaneously or as a result of
> exposure to other carcinogens. Radiation exposure may be only the initiating
> step that may or may not eventually lead to cancer. Genetic effects may appear
> in the exposed person's direct offspring, or may appear several generations
> later, depending on whether the altered genes are dominant or recessive.
>
> Although radiation is known to cause cancers at high doses and high dose rates,
> currently there are no data to unequivocally establish the occurrence of cancer
> following exposure to low doses and dose rates -- below about 20,000 mrem (200
> mSv). Studies of a population exposed to chronic low-levels of radiation above
> normal background have shown no biological effects. This population includes
> occupationally exposed radiation workers and people living in areas having high
> levels of background radiation [above 1,000 mrem (10 mSv) per year].
>
> In the absence of sufficient data to the contrary, the radiation protection
> community conservatively assumes that any amount of radiation may pose some risk
> for causing cancer and hereditary effects, and that the risk is higher for
> higher level doses. The NRC's dose limits for both radiation workers and members
> of the public were developed on that basis. (NRC regulations and radiation
> exposure limits are contained in Title 10 of the Code of Federal Regulations
> under Part 20.)
>
> September 1999
>
> =====
>
> Thanks,
>
> Dave Lochbaum
> Nuclear Safety Engineer
> Union of Concerned Scientists
> 1616 P Street NW Suite 310
> Washington, DC 20036
> (202) 332-0900
> (202) 332-0905 fax
> website:  www.ucsusa.org
>

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