32.2 Biological Effects of Ionizing Radiation

There are many conflicting things about the effects of ionizing radiation.

It can cause cancer, burns, and hair loss, yet it is used to cure cancer.
There is an underlying simplicity in nature.

Let's take a look at how cells work.

Cells have long, double-helical DNA molecule containing chemical codes called genetic codes that govern the function and processes undertaken by the cell.
The double-helical structure of DNA was the subject of the research that led to the award of the prize.
Break in chemical bonds or other changes in the structural features of the DNA chain can lead to changes in the genetic code.
Human cells can have as many as a million individual instances of damage per day.
There are codes in the DNA that check if it can repair itself or is damaged.
It's similar to an auto check and repair mechanism.
The integrity of the genetic code and the normal functioning of the entire organisms are dependent on the repair ability of DNA.
The rate of repair depends on a number of factors.
A cell with a damaged ability to repair DNA can do one of the following.

programmed cell death is when the cell can commit suicide.

The unregulated cell division can lead to tumors and cancers.

Most types of cancer are caused by ionizing radiation because it damages the DNA, which is critical in cell reproduction.

Cancer cells are more likely to be killed by radiation than normal cells.
Ionizing radiation can cause cancer because of a malfunction of cell reproduction.
Ionizing radiation can be a cure and cause.

We need a radiation dose unit that is related to the biological effects of ionizing radiation.

Radiation effects are assumed to be proportional to the amount of ionization produced in the biological organisms.
The amount of energy deposited is proportional to the amount of ionization.

You divide the energy absorbed by the tissue by the radiation dose.

The affected region must be specified, along with the numerical dose in rads.

The rad is still used.

The effects of the energy per kilogram in 1 rad are significant.
A few eV is all that is needed for a single ion.
A lot of ion pairs can be created by a small amount of ionizing energy.

The effects of ionizing radiation can be directly proportional to the dose in rads, but they also depend on the type of radiation and the type of tissue.

The effects depend on whether the radiation is x-ray or some other type of ionizing radiation.
In the earlier discussion of the range of ionizing radiation, it was noted that energy is deposited in a series of ionizations and not in a single interaction.
The number of ion pairs is proportional to the amount of ionizing energy deposited.
Short-range particles have greater biological effects than long-range particles because they are more difficult to repair.

The image shows the creation of ion in cells.

The damage created by it is harder to repair because of its shorter range.
The RBE for s is greater than the RBE for s because they create the same amount of ionization.

The dose in rem would be if a person had a whole-body dose of radiation.

The dose in rem would be if the person had a whole-body dose of radiation.
The effect on the person would be 20 times greater than the effect on the deposited energy.

The RBEs in Table 32.2 yield some insights.

The eyes are more sensitive to radiation because the cells of the lens do not repair themselves.
Neutrons cause more damage than rays because they cause secondary radiation when they are captured.
Three of the most common types of radiation are higher-energy s, s, and x-rays.
The values of the dose in rem and rad are the same for those types of radiation.
1 rad of radiation is the same as 1 rem.
rads are quoted more than rem.
The table summarizes the units used for radiation.

"Activity" refers to the radioactive source while "dose" refers to the amount of energy from the radiation that is deposited in a person or object.

If a person is far away from the source, a high level of activity doesn't mean much.

The activity of a source is dependent on the quantity of material and the half-life.
A short half-life will cause more disintegrations.
The activity decreases as the equation shows.

It is difficult to determine the relative biological effectiveness.

The effects of radiation on humans can be divided into two categories: immediate and long-term.

Table 32.4 shows the effects of whole-body exposure in a day.

If the exposure is spread out over a longer period of time, more doses are needed to cause the effects listed.
The body can partially repair the damage.
There is no way to know if a person has been exposed to less than 10 mSv.

White blood cell counts can decrease.

Hair loss, severe blood damage, and deaths are all related to nausea, vomiting, and hair loss.

If not treated, lethal to 50% of the population within 32 days.

2ply by 100 to get the dose in rem.

Immediate effects are explained by the effects of radiation on cells.

Since blood cells are the most rapidly reproducing cells in the body, a change in blood count is a sign that a person has been exposed to radiation.

Decreases in hair and nausea are observed at higher doses.
The destruction of cells in the lining of the digestive system causes nausea.
The hair cells become thin and break off when the growth slows.
The lowest doses that cause deaths weaken the immune system because of the loss of white blood cells.

There are two known long-term effects of radiation.

Both are caused by the interference of radiation with cell reproduction.
The risk of cancer is well known from studies of exposed groups.
There are people exposed to radium who have been fully documented.
The Chernobyl victims will be studied for a long time.
There has been an increase in childhood cancer.
The risk of cancer caused by radiation is assumed to be proportional to the risk of cancer caused by high doses.
Any dose of radiation, no matter how small, has a risk to human health.
The long-term effects of radiation are cumulative and there is little self-repair, according to some evidence.
The risk of skin cancer from UV exposure is known to be cumulative.

There is a period of about 2 years for leukemia and 15 years for most other forms of cancer.

The person is at risk for at least 30 years.
The risk of dying from cancer caused by radiation is 10 in a million, which can be written as.

If a person receives a dose of 1 rem, his risk of dying from radiation-induced cancer is 10 in a million and that risk continues for 30 years.

300 in a million is the lifetime risk.
It is impossible to detect demographically an increase due to a 1 rem exposure due to the fact that 20 percent of all deaths are from cancer.
A 3 percent risk can be observed in the presence of a 20 percent normal or natural incidence rate, if 100 rem (1 Sv) is the dose received by the average Hiroshima and Nagasaki survivor.

The incidence of genetic defects caused by radiation is less than that caused by cancer deaths.

The lifetime risk of a genetic defect due to a 1 rem exposure is 100, but the normal incidence is 60,000.

It is nearly impossible to get evidence of a small increase.
There is no evidence of increased genetic defects in the offspring of survivors.
Animal studies don't seem to correlate well with humans.
The approach to safety for both cancer and genetic defects has been to use the linear hypothesis, which is likely to be an overestimate of the risks of low doses.
Some researchers claim that low doses are beneficial.
Some repair mechanisms may be helped by low levels.
Positive effects may be a problem at high doses.

The average person is not exposed to large amounts of radiation.

The average dose of Cosmic rays is 0.40 mSv/y, but it depends on altitude and latitude.
An example of the variation of radiation dose with altitude is the airline industry.
The personnel show an average of 2 mSv/y.
You can get an exposure of 0.02 to 0.03 mSv on a 12-hour flight.

The amount of radioactivity in the Earth varies greatly by location.

Some places have concentrations of thorium that are ten times higher than the average value.

We get internal doses from our food and liquids.

Potassium and uranium are contained in thefertilizers.
We are all a little radioactive.
Carbon-14 has more radioactivity than fertilizers.
x-rays are the majority of medical and dental diagnostic exposures.
With improved techniques, the x-ray dose is becoming much smaller.
The table shows the typical doses received during the x-ray examination.
There was a large dose from the test.
Less than 20 percent of x-ray procedures done today are computed tomography scans, but they account for 50 percent of the annual dose received.

In buildings with low air exchange with the outside world, Radon is more pronounced.

Most of the soil contains some, but radon is lower in some soils and higher in others.

There is a chance that Radon can diffuse from the soil into the home.

The estimated exposure is controversial.
According to recent studies, there is more radon in homes than has been realized, and it is thought that it may be responsible for 20 percent of lung cancer in people who also smoke.
Many countries have introduced limits on allowable concentrations in indoor air, often requiring the measurement of radon concentrations in a house prior to its sale.
It could be argued that low-level radiation is less dangerous than previously thought because of the higher levels of radon exposure and their geographic variability.

People can be exposed to radiation.

The highest occupational whole-body dose that is allowed is 20 to 50 mSv/y and is rarely reached by medical and nuclear power workers.
The hands can get higher doses.
The reproductive organs and the fetus of pregnant women can be had for much lower doses.
The public cannot be exposed to more than 0.05 mSv/y (5 mrem/y) if they are caused by nuclear power.
This was exceeded in the United States at the time of the Three Mile Island accident.
Chernobyl is not the same as the other stories.

A variety of radiation detectors are monitored to assure radiation safety.

The dose has been lowered to about 1 mSv/y.

When an x-ray is taken, these are used to protect the patient and the dental technician.

Shielding can be provided by any material.
The distance from the source increases the spread of radiation.
The smaller the dose received by the person, the less time they are exposed to a source.
Faster films that require less exposure time have led to a decrease in the dose of medical diagnostics.

To get dose in mrem/y, you have to multiplication by 100.

A lead apron is placed over the dental patient and shielding surrounds the x-ray tube to limit exposure to tissue other than the tissue that is being imaged.

Fast films reduce exposure to the imaged tissue.
A technician stands a few meters away from a lead glass window to reduce her occupational exposure.

Determine if a person is exposed to ionizing radiation by examining the situation.

Identifying the unknowns will help determine exactly what needs to be determined in the problem.

A dose calculation is one of the most straightforward problems.

A list of what can be inferred from the problem can be made.

Information on the type of radiation, energy per event, activity, and mass of tissue affected can be found.

You need to know how much energy is deposited.

Depending on the information, this may take one or more steps.

The deposited energy should be divided by the mass of the affected tissue.

If you want to calculate the dose in Gy, use the definition of 1 J/kg.

Determine the RBE of the radiation to calculate the dose in mSv.

The numbers for diagnostic, occupational, and therapeutic exposures are given in the text.

calculate the dose in rem/y for the lungs of a weapons plant employee who inhales and retains an activity in an accident The plutonium decays by emission of a 5.23-MeV particle, and the mass of affected lung tissue is 2.00 kg, so you may assume the higher value of the RBE for s from Table 32.2.

The mass of tissue affected by the energy deposited is divided by the RBE.

The main task in this example is to find the energy deposited in one year.
Since the activity of the source is given, we can calculate the number of decays, multiply by the energy per decay, and convert MeV to joules to get the total energy.

The dose is given to two digits because the RBE is only known to two digits.

By any standard, this yearly radiation dose is high and will have a devastating effect on the health of the worker.
plutonium has a long radioactive half-life and is not easily eliminated by the body, so it will remain in the lungs.
The effects are 10 to 20 times worse if you are an emitter.
Part of the justification for claims that plutonium is the most toxic substance is that an activity is created by only an end-of-chapter problem to verify.

The actual hazard depends on how likely it is to be spread among a large population.

The plutonium it put into the environment has nothing to do with the Chernobyl disaster.