RADIATION SAFETY_Mar 2011_share

Radiation Safety:

Radiation Safety

Effects of Radiation:

Effects of Radiation Although we cannot see or feel the presence of radiation, it can be detected and measured with quite simple radiation measuring instruments.

Radiation Dose:

Radiation Dose The biological effects of ionizing radiation vary with the type and energy A measure of the risk of biological harm is the dose of radiation that the tissues receive

Radiation Dose:

Radiation Dose The unit of absorbed radiation dose is the sievert ( Sv ). Since one sievert is a large quantity, radiation doses normally encountered are expressed in millisievert ( mSv ) or microsievert (µ Sv ) which are one-thousandth or one millionth of a sievert respectively. For example, one chest X-ray will give about 0.1 mSv of radiation dose.

Radiation Dose:

Radiation Dose On average, our radiation exposure due to all natural sources amounts to about 2.4 mSv a year. The largest source of natural radiation exposure comes from varying amounts of uranium and thorium in the soil around the world.

Radiation Dose:

Radiation Dose Radiation exposure due to cosmic rays is very dependent on altitude, and slightly on latitude. People who travel by air, thereby, increase their exposure to radiation. People also receive internal exposure from radioactive elements which we take into our bodies through food and water and through the air we breathe. In addition, we have radioactive elements (Potassium 40, Carbon 14, Radium 226) in our blood or bones.

Radiation Dose:

Radiation Dose We are exposed to varying amounts of radiation from sources such as: dental other medical X-rays, industrial uses of nuclear techniques and other products i.e. ionization smoke detectors, etc.

Radiation Dose:

Radiation Dose We are also exposed to radiation from radioactive elements contained in fallout from: nuclear explosives testing, routine normal discharges from nuclear and coal power stations.

Radiation Protection:

Radiation Protection In 1928, an independent non-governmental body of experts in the field, the International X-ray and Radium Protection Committee was established. Renamed later - the International Commission on Radiological Protection (ICRP). Its purpose is to establish basic principles for and issue recommendations on, radiation protection.

Radiation Protection:

Radiation Protection In 1955, UN Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). UNSCEAR is directed to: assemble, study and disseminate information on observed levels of ionizing radiation radioactivity (natural and man-made) in the environment on the effects of such radiation on man and the environment.

Radiation Protection:

Radiation Protection The International Atomic Energy Agency (IAEA) is an international organization (established in 1957) that seeks: to promote the peaceful use of Nuclear Energy, and to inhibit its use for any military purpose, including Nuclear Weapons.

Radiation Protection:

Radiation Protection Basic approaches to radiation protection are consistent all over the world. The ICRP recommends that any exposure above the natural background radiation should be kept As Low As Reasonably Achievable (ALARA), but below the individual dose limits.

Radiation Protection:

Radiation Protection DOSE LIMITS The individual dose limit for radiation workers averaged over 5 years is 100 mSv , and For members of the general public, is 1 mSv per year.

Radiation Protection:

Radiation Protection The dose limits have been established based on a prudent approach with following assumptions: No threshold dose below which there would be no effect. Any additional dose will cause a proportional increase in the chance of a health effect. Note: This relationship has not yet been established in the low dose range where the dose limits have been set.

Radiation Protection:

Radiation Protection The individual dose must be kept ALARA Allowance for future sources or practices must be kept in mind so that the total dose received by an individual member of the public does not exceed the dose limit.

Radiation Protection:

Radiation Protection Normally, average annual dose received by radiation workers is found to be considerably lower than the individual dose limits. Good radiation protection practice can thus result in low radiation exposure to workers.

At What Level is Radiation Harmful?:

At What Level is Radiation Harmful? The effects of radiation at high doses and dose rates are reasonably well documented. A very large dose (the whole body) over a short time will result in the death within days. Lesson learned – health records of the survivors of the bombing of Hiroshima and Nagasaki.

At What Level is Radiation Harmful?:

At What Level is Radiation Harmful? Some of the health effects of exposure to radiation do not appear unless a certain quite large dose is absorbed. Other effects, especially cancers are readily detectable and occur more often in those with moderate doses . At lower doses and dose rates, there is a degree of recovery in cells and in tissues.

At What Level is Radiation Harmful?:

At What Level is Radiation Harmful? Experimental evidence from animal studies that exposure to radiation can cause genetic effects. The studies of the survivors of Hiroshima and Nagasaki give no indication of this for humans.

At What Level is Radiation Harmful?:

At What Level is Radiation Harmful? For low levels of radiation exposure, the biological effects are so small they may not be detected. They could be detected only by careful analysis of a large volume of statistical data. The body has repair mechanisms against damage induced by radiation as well as by chemical carcinogens.

At What Level is Radiation Harmful?:

At What Level is Radiation Harmful? Have to be distinguished from those of a number of other agents which might also cause genetic disorders, but whose effect may not be recognized until the damage has been done for example: thalidomide, once prescribed for pregnant women as a tranquilizer . Resolution of the scientific debate will not come via epidemiology but from an understanding of the mechanisms through molecular biology.

At What Level is Radiation Harmful?:

At What Level is Radiation Harmful? Consequently, biological effects of radiation on living cells may result in 3 outcomes: injured or damaged cells repair themselves, resulting in no residual damage cells die, much like millions of body cells do every day, being replaced through normal biological processes cells incorrectly repair themselves resulting in a biophysical change.

At What Level is Radiation Harmful?:

At What Level is Radiation Harmful?

At What Level is Radiation Harmful?:

At What Level is Radiation Harmful?

At What Level is Radiation Harmful?:

At What Level is Radiation Harmful? The associations between radiation exposure and the development of cancer - exposed to relatively high levels of ionizing radiation (e.g., Japanese atomic bomb survivors, and recipients of selected diagnostic or therapeutic medical procedures). Cancers associated with high-dose exposure (greater than 500 mSv include leukemia, breast, bladder, colon, liver, lung, esophagus, ovarian, multiple myeloma, and stomach cancers.

At What Level is Radiation Harmful?:

At What Level is Radiation Harmful? The period of time between radiation exposure and the detection of cancer is known as the latent period and can be many years. Those cancers are indistinguishable from those that occur naturally or as a result of exposure to other carcinogens.

At What Level is Radiation Harmful?:

At What Level is Radiation Harmful? Currently there are no data to establish occurrence of cancer following exposure to low doses and dose rates – below 100 mSv . Those people living in areas having high levels of background radiation – above 10 mSv per year have shown no adverse biological effects.

At What Level is Radiation Harmful?:

At What Level is Radiation Harmful? High radiation doses tend to kill cells, while low doses tend to damage or alter the genetic code (DNA) of irradiated cells. High doses can kill so many cells that tissues and organs are damaged immediately.

At What Level is Radiation Harmful?:

At What Level is Radiation Harmful? A rapid body response to Radiation is called Acute Radiation Syndrome (ARS) . The higher the radiation dose, the sooner the effects of radiation will appear and the higher the probability of death. This ARS was observed in many atomic bomb survivors in 1945 and emergency workers responding to the 1986 Chernobyl nuclear power plant accident.

At What Level is Radiation Harmful?:

At What Level is Radiation Harmful? Approx 134 plant workers and firefighters responding to the fire at the Chernobyl received high radiation doses –800 to 16,000 mSv – and suffered from acute radiation sickness. Of these, 28 died within the first three months. Two more patients died during the first days as a result of combined injuries from the fire and radiation.

At What Level is Radiation Harmful?:

At What Level is Radiation Harmful? It is not possible to indicate what dose is needed to be fatal because radiation affects different people differently. It is believed that 50% of a population would die within 30 days after receiving a dose of between 3500 to 5000 mSv to the whole body, over a period ranging from a few minutes to a few hours.

At What Level is Radiation Harmful?:

At What Level is Radiation Harmful? Depending on the health of the individuals before the exposure and the medical care received after the exposure. Similar exposure of only parts of the body will likely lead to more localized effects, such as skin burns.

At What Level is Radiation Harmful?:

At What Level is Radiation Harmful? For low doses – less than 100 mSv – long periods of time (years) don't cause an immediate problem to any body organ. The effects of low doses of radiation, if any, would occur at the cell level, and thus changes may not be observed for many years (usually 5-20 years). Genetic effects and the development of cancer are the primary health concerns.

At What Level is Radiation Harmful?:

At What Level is Radiation Harmful? The likelihood of cancer occurring after radiation exposure is about five (5) times greater than a genetic effect for example: increased still births, congenital abnormalities, infant mortality, childhood mortality and decreased birth weight.

At What Level is Radiation Harmful?:

At What Level is Radiation Harmful? Genetic effects are the result of a mutation produced in the reproductive cells of an exposed individual that are passed on to their offspring. 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.

At What Level is Radiation Harmful?:

At What Level is Radiation Harmful? Radiation-induced genetic effects have been observed in laboratory animals (given very high doses of radiation)/ No evidence of genetic effects has been observed among the children born to atomic bomb survivors from Hiroshima and Nagasaki.

Nuclear & Radiological Event Scale:

Nuclear & Radiological Event Scale

At What Level is Radiation Harmful?:

At What Level is Radiation Harmful? Thank you for your attention Q&A