What happens if radiation is released

When inside the human body, alpha particles can cause damage to the cells and to DNA as their size makes it more likely that it will interact with matter. If the dose is too high for repairs to be made satisfactorily, there is a potential increase in the risk of getting cancer later in life.

Equally, its small size results in its ionising power being considerably smaller than that of alpha particles by about 10 times. The smaller the particle, the lower the risk of it colliding with parts of the atom which, in turn, lowers the risk of damage. These are high-energy electromagnetic waves much the same as X-rays.

They are emitted in many radioactive decays and may be very penetrating, so require more substantial shielding. The energy of gamma rays depends on the particular source. Gamma rays are the main hazard to people dealing with sealed radioactive materials used, for example, in industrial gauges and radiotherapy machines. Radiation dose badges are worn by workers in exposed situations to monitor exposure. All of us receive about 0. Gamma activity in a substance e. X-rays are also electromagnetic waves and ionizing, virtually identical to gamma rays, but not nuclear in origin.

They are produced in a vacuum tube where an electron beam from a cathode is fired at target material comprising an anode, so are produced on demand rather than by inexorable physical processes. However the effect of this radiation does not depend on its origin but on its energy. X-rays are produced with a wide range of energy levels depending on their application.

Cosmic radiation consists of very energetic particles, mostly high-energy protons, which bombard the Earth from outer space. They comprise about one-tenth of natural background exposure at sea level, and more at high altitudes.

Neutrons are uncharged particles mostly released by nuclear fission the splitting of atoms in a nuclear reactor , and hence are seldom encountered outside the core of a nuclear reactor.

Fast neutrons can be very destructive to human tissue. Neutrons are the only type of radiation which can make other, non-radioactive materials, become radioactive. In order to quantify how much radiation we are exposed to in our daily lives and to assess potential health impacts as a result, it is necessary to establish a unit of measurement. The basic unit of radiation dose absorbed in tissue is the gray Gy , where one gray represents the deposition of one joule of energy per kilogram of tissue.

However, since neutrons and alpha particles cause more damage per gray than gamma or beta radiation, another unit, the sievert Sv is used in setting radiological protection standards. This weighted unit of measurement takes into account biological effects of different types of radiation and indicates the equivelent dose. One gray of beta or gamma radiation has one sievert of biological effect, one gray of alpha particles has 20 Sv effect and one gray of neutrons is equivalent to around 10 Sv depending on their energy.

Since the sievert is a relatively large value, dose to humans is normally measured in millisieverts mSv , one-thousandth of a sievert. Note that Sv and Gy measurements are accumulated over time, whereas damage or effect depends on the actual dose rate , e.

Quantities of radioactive material are commonly estimated by measuring the amount of intrinsic radioactivity in becquerels — one Bq of radioactive material is that amount which has an average of one disintegration per second, i.

This may be spread through a very large mass. Though the intrinsic radioactivity is the same, the radiation dose received by someone handling a kilogram of high-grade uranium ore will be much greater than for the same exposure to a kilogram of separated uranium, since the ore contains a number of short-lived decay products see section on Radioactive Decay , while the uranium has a very long half-life. The Working Level Month WLM has been used as a measure of dose for exposure to radon and in particular, radon decay products b.

Since there is radioactivity in many foodstuffs, there has been a whimsical suggestion that the Banana Equivalent Dose from eating one banana be adopted for popular reference. This is about 0. Radiation can arise from human activities or from natural sources.

Most radiation exposure is from natural sources. These include: radioactivity in rocks and soil of the Earth's crust; radon, a radioactive gas given out by many volcanic rocks and uranium ore; and cosmic radiation. Helpful depictions of routine sources of radiation can be found on the information is beautiful and xkcd websites.

In the USA by it averaged about half of the total. This radiation is no different from natural radiation except that it can be controlled. X-rays and other medical procedures account for most exposure from this quarter. On average, nuclear power workers receive a lower annual radiation dose than flight crew, and frequent flyers in hours would receive 1 mSv.

In comparison, the average dose received by the public from nuclear power is 0. Naturally occurring background radiation is the main source of exposure for most people, and provides some perspective on radiation exposure from nuclear energy. Potasssium, uranium and thorium with their decay products are the main source.

The average dose received by all of us from background radiation is around 2. The highest known level of background radiation affecting a substantial population is in Kerala and Madras states in India where some , people receive doses which average over 15 millisievert per year from gamma radiation, in addition to a similar dose from radon. Lifetime doses from natural radiation range up to several thousand millisievert.

However, there is no evidence of increased cancers or other health problems arising from these high natural levels. The millions of nuclear workers that have been monitored closely for 50 years have no higher cancer mortality than the general population but have had up to ten times the average dose.

People living in Colorado and Wyoming have twice the annual dose as those in Los Angeles, but have lower cancer rates. Cancer Res. Drinking the water is also said to have antioxidant effects. These claims are not known to be endorsed by any public health authority. Radon is a naturally occurring radioactive gas resulting from the decay of uranium, which concentrates in enclosed spaces such as buildings and underground mines, particularly in early uranium mines where it sometimes became a significant hazard before the problem was understood and controlled by increased ventilation.

Radon has decay products that are short-lived alpha emitters and deposit on surfaces in the respiratory tract during the passage of breathing air. At high radon levels, this can cause an increased risk of lung cancer, particularly for smokers. Smoking itself has a very much greater lung cancer effect than radon. People everywhere are typically exposed to around 0. Where deemed necessary, radon levels in buildings and mines can be controlled by ventilation, and measures can be taken in new constructions to prevent radon from entering buildings.

Here, a study Mortazavi et al, showed that the highest lung cancer mortality rate was where radon levels were normal, and the lowest rate was where radon concentrations in dwellings were highest. Above this, workers should be considered as occupationally exposed, and subject to the same monitoring as nuclear industry workers.

Public exposure to natural radiation e. The average occupational exposure of each person monitored at Naval Reactors' facilities since is 1. Some of the ultraviolet UV radiation from the sun is considered ionizing radiation, and provides a starting point in considering its effects.

Sunlight UV is important in producing vitamin D in humans, but too much exposure produces sunburn and, potentially, skin cancer. Skin tissue is damaged, and that damage to DNA may not be repaired properly, so that over time, cancer develops and may be fatal. Adaptation from repeated low exposure can decrease vulnerability.

But exposure to sunlight is quite properly sought after in moderation, and not widely feared. Our knowledge of the effects of shorter-wavelength ionizing radiation from atomic nuclei derives primarily from groups of people who have received high doses.

The main difference from UV radiation is that beta, gamma and X-rays can penetrate the skin. The risk associated with large doses of this ionizing radiation is relatively well established.

However, the effects, and any risks associated with doses under about mSv, are less obvious because of the large underlying incidence of cancer caused by other factors. Benefits of lower doses have long been recognised, though radiation protection standards assume that any dose of radiation, no matter how small, involves a possible risk to human health.

However, available scientific evidence does not indicate any cancer risk or immediate effects at doses below mSv per year. At low levels of exposure, the body's natural mechanisms usually repair radiation damage to DNA in cells soon after it occurs see following section on low-level radiation.

However, high-level irradiation overwhelms those repair mechanisms and is harmful. Dose rate is as important as overall dose. High absorbed dose is defined as more than about mGy. For beta and gamma radiation, these figures can be taken as mSv equivalent dose. It involves scientists from over 20 countries and publishes its findings in major reports.

It had been asked in "to clarify further the assessment of potential harm owing to chronic low-level exposures among large populations and also the attributability of health effects" to radiation exposure. It said that while some effects from high acute doses were clear, others including hereditary effects in human populations were not, and could not be attributed to exposure, and that this was especially true at low levels.

UNSCEAR also addressed uncertainties in risk estimation relating to cancer, particularly the extrapolations from high-dose to low-dose exposures and from acute to chronic and fractionated exposures.

Epidemiological studies continue on the survivors of the atomic bombing of Hiroshima and Nagasaki, involving some 76, people exposed at levels ranging up to more than 5, mSv. These have shown that radiation is the likely cause of several hundred deaths from cancer, in addition to the normal incidence found in any population f. In Western countries, about a quarter of people die from cancers, with smoking, dietary factors, genetic factors and strong sunlight being among the main causes.

Radiation is a weak carcinogen, but undue exposure can certainly increase health risks. In , the US National Cancer Institute NCI found no evidence of any increase in cancer mortality among people living near to 62 major nuclear facilities. The NCI study was the broadest of its kind ever conducted and supported similar studies conducted elsewhere in the USA as well as in Canada and Europe.

About 60 years ago it was discovered that ionizing radiation could induce genetic mutations in fruit flies. Intensive study since then has shown that radiation can similarly induce mutations in plants and test animals. However there is no evidence of inherited genetic damage to humans from radiation, even as a result of the large doses received by atomic bomb survivors in Japan. In a plant or animal cell the material DNA which carries genetic information necessary to cell development, maintenance and division is the critical target for radiation.

This may result in death of the cell or development of a cancer, or in the case of cells forming gonad tissue, alterations which continue as genetic changes in subsequent generations.

Most such mutational changes are deleterious; very few can be expected to result in improvements. The relatively low levels of radiation allowed for members of the public and for workers in the nuclear industry are such that any increase in genetic effects due to nuclear power will be imperceptible and almost certainly non-existent.

When that happens in a molecule of DNA it can cause mutations, which can lead to cancer down the track. And ionising a protein can mess with its shape and function — not something you want in the molecules that coordinate most of the chemistry in our cells.

Our bodies are full of water, and almost all cells have DNA, but some cells and tissues are more susceptible to damage from nuclear radiation than others. The cells and organs that are most affected by nuclear radiation are the ones that are actively reproducing, because the DNA is more exposed when the cell is in the process of dividing. Blood cells have the highest turnover rate in our bodies, so the tissue where they are produced — the rapidly dividing cells of the bone marrow — is the most susceptible to radiation damage.

The damage to bone marrow in high doses — and complete destruction of it in very high doses — impairs our immune system by not replacing our white blood cells. Long-term exposure to lower doses can lead to cancerous DNA mutations in the marrow, which can lead to the blood cancer leukaemia in people exposed through work or location.

The cells lining the digestive system are also fast-dividing, so they can cope with the physical and chemical assault of digesting our food. Gastrointestinal damage contributes to the symptoms of acute radiation syndrome in people who are exposed to high doses.

Developing foetuses are, of course, incredibly susceptible to radiation, while slow-dividing tissues like muscle and nerve cells are far less sensitive. And healthy tissues and organs are not the only cells that regularly reproduce — tumours are literally balls of cells that are dividing out of control, which is why radiation therapy can be effective in destroying them. The good blood supply feeding tumours helps too, because the radiation interacts with the dissolved oxygen in the blood as well.

That leads to the production of free radicals which attack the nearby cells, amplifying the radiation's effect. Exposure to external radiation is one thing, but ingesting radioactive particles takes the damage to another level. Inhaling or swallowing radioactive material delivers the source of radiation directly to your cells, increasing the risk of cancer developing in the tissues where they accumulate.

Radioactive iodine iodine blown into the atmosphere by the Chernobyl explosion caused a large number of cases of thyroid cancer in people who drank contaminated milk. Having been released in the clouds of radioactive material following the explosion, the iodine — a by-product of nuclear fission reactions — landed on fields where it was swallowed by cows. Iodine is essential for the normal function of the thyroid gland, and with its knack for attracting iodine the gland gets a concentrated dose of iodine when contaminated milk is drunk.

Types of Contamination. More Information Infographic: What's the difference between radiation contamination and exposure? To receive email updates about this page, enter your email address: Email Address. What's this. Related Pages. Contact Us Calendar Employment. Links with this icon indicate that you are leaving the CDC website.

Linking to a non-federal website does not constitute an endorsement by CDC or any of its employees of the sponsors or the information and products presented on the website. You will be subject to the destination website's privacy policy when you follow the link. CDC is not responsible for Section compliance accessibility on other federal or private website. Some studies have shown increases in the rates of childhood cancer in children exposed to radiation before birth. Cancer - Cancer is the most common non-threshold effect of high radiation doses in humans.

The cancers caused by radiation are no different from cancers due to other causes. Estimates of cancer risk for specific doses of radiation are based on many studies of groups of people who were exposed to high doses of radiation. These include the survivors of the atomic bombings in Japan, people who were exposed to radiation for medical reasons, and workers who were exposed to high doses of radiation on the job.

The survivors of the World War II atomic bomb explosions in Hiroshima and Nagasaki were exposed to an average radiation dose equivalent of 24 rem, and their health has been carefully studied since This study is the most important source of information on the risk of cancer from radiation exposure because it involves a large number of individuals who received whole body radiation exposure.

It provides information on the risk of increased cancer to all organs and on the variation of risk with age at the time of exposure. Radiation has been found to induce cancer in most body tissues and organs. Different tissues and organs, however, show varying degrees of sensitivity.

The tissues and organs showing high sensitivity include bone marrow leukemia , breasts, thyroid glands and lungs. In contrast, there is no clear evidence that radiation causes cancer of the cervix or prostate.

Some people are more sensitive to harmful effects of radiation than others. There are a number of factors that influence an individual's sensitivity to radiation. These factors include age, gender, other exposures and genetic factors. Age - In general, exposed children are more at risk than adults. Breast cancer risk among women exposed to radiation is greatest among women who were exposed before age 20, and least when exposure occurred after menopause.

Also, exposed children are at greater risk of radiation-induced thyroid cancer than adults. Gender - In women, the risk of breast and ovarian cancers from radiation is high, but there is no clear evidence that radiation causes breast or prostate cancers in men. Females are also seen to have more radiation induced thyroid cancer than males. Other Exposures - Underground miners exposed to high levels of radon have increased risk of lung cancer, and those who smoke have an even greater risk. Exposure to ultraviolet radiation from the sun following the use of x-rays to treat scalp ringworm conditions increases the risk of developing skin cancer in the area of the skin exposed to both types of radiation.

Genetic Factors - Individuals with certain pre-existing genetic diseases have increased sensitivity to radiation, especially if they receive radiation therapy.

For example, children genetically predisposed to cancer of the retina retinoblastoma and who are treated with radiation are at increased risk of developing bone cancer following treatment. Patients with ataxia telangiectasia AT , a rare genetic disorder, are unusually sensitive to tissue damage from radiation therapy, but there is no clear evidence that they are at increased risk of radiation induced cancer.

This means that if 1, people were exposed to 10 rem each, 8 would be expected to die of cancer induced by the radiation. These deaths are in addition to about cancer deaths that result from other causes. If the 10 rem were received over a period of weeks or months, the extra lifetime risk could be reduced to 0. These risk factors are average values for a population similar to that of the United States. These percentages are not precise predictions of risk, especially at low radiation doses and dose rates.

At doses comparable to natural background radiation 0. The risk of increased cancer incidence is well established for doses above 10 rem. For low doses, it has not been possible to scientifically determine if an increased risk exists, but many scientists believe that small doses of radiation do lead to increased cancer risk, and that the degree of risk is directly proportional to the size of the dose.

Risk estimates from low doses are obtained by extrapolation from high dose observations. Because of the potential for harm from exposure to radiation, radiation protection programs are designed to protect both workers and the general public, their descendants and the environment, while still allowing society to benefit from the many valuable uses of radiation.

Current radiation protection systems are based on the following principles:. All users of radiation sources in New York State are regulated by state, federal and local government agencies. Users are required to implement radiation safety programs that reflect these principles. They are routinely inspected to assure that all operations are carried out safely. Exposure to indoor radon contributes a large portion of the total average dose.

Measurements of radon in New York State homes made since have identified many areas with elevated indoor radon levels. Exposure can be reduced by testing the home for radon and implementing measures to reduce radon levels, if necessary. For additional information on radon, its measurement and mitigation, contact the New York State Department of Health at Also, a person should receive only x-ray examinations that his or her health care provider thinks are truly necessary for an accurate diagnosis.

Alternative, non-x-ray tests should be used instead, if available. However, one should not refuse an x-ray examination that a doctor feels is necessary. Recent advances in molecular genetics and microbiology have increased our understanding of cancer development.

It is hoped that further research will provide additional information on the risk of radiation-induced cancer and genetic effects, especially at low doses. Absorbed Dose is the amount of radiation absorbed in matter measured in terms of energy per unit mass. The unit traditionally used for absorbed dose is the "rad," but a new unit called a "gray" has been introduced for international use and will eventually replace the rad.

One gray equals rads. Alpha Particles are charged particles that are emitted from some radioactive materials such as radium and radon.