Radiation sources and types in occupational and environmental exposure

Radiation Safety in Industrial Hygiene

Nature has it that all living things depend on a certain type of radiation to survive. This is evident in many ways for instance we can see because our eyes sense and become aware of the radiation in the form of light; then there is infrared radiation that allows is to keep ourselves warm in the cold weather, radiation is used for cooking, whether it is on the stove or in the microwave. Radiowaves are used for long distance communication by using sound or picture; and ultraviolet radiation is used for medical treatment or for putting on a good suntan. Even though some forms of radiation can travel long distances, it can be stopped by employing the correct absorbers: starlight can transgress galaxies but then using a piece of paper it can also be stopped; radiowaves are also capable of travelling huge distances but can be absorbed by metal like substances. Just as light travels in straight lines, so does ionising radiation til it is absorbed by materials.

It was back in the twentieth century, that "ionising radiation" was discovered. Ionising radiation is found everywhere and supports our natural background radiation. It is also found in many sources such as the sun, outer-space, the rocks and soil beneath our feet, the buildings we inhabit, the air we breathe, the food and drink we consume, and even in our bodies.

Types and sources of ionising radiation

Inclusion to X-rays, are three types of ionising radiation called alpha, beta and gamma. Alpha rays also called the helium nuclei can be stopped by paper, beta rays also known as high-speed electrons are stopped less easily, and gamma rays need lead or concrete to stop them. It is a known fact that since one cannot glow in the dark due to light similarly, a chest X-ray will not make one radioactive, therefore, ionising radiations will not make one radioactive. This is because in industries in a reactor there are billions of free nuclear projectiles called neutrons, which on absorption into any material cause it to become radioactive. This leads to the material producing its own radiation.

A person's annual radiation dosage originates from the decay of natural radioactivity because the presence of bricks and mortar escalates the concentration of a radioactive gas called radon. Radon is produced naturally from the radioactive decay of uranium and thorium, found in rocks, soil, bricks, mortar, tiles and concrete. Plunging ventilation to conserve energy in turn causes an increase in the radon concentration in the air we breathe. Another way to increase radon concentration is by using bore water, especially in hot showers. Other sources of smaller dosages of everyday radiation come from cosmic rays and from the natural radioactivity found in the consumption of our food and drink. The man-made sources of radiation are from the use of medical technology, such as the usage of X-rays for radiography and tomography, and radioactivity in nuclear medicine. According to a study, a person absorbs more than 2000 microsieverts a year of natural background radiation. Other sources of additional doses depend on the medical use of radiation according to a person's medical history. Dental X-rays account for one-tenth the annual background while multiple X-rays in combination with a barium enema, accounts for a huge percentage of the annual background radiation. Radiation doses are the highest in cancer therapy fro cancer patients..

Some people get more radiation than others since study shows that cosmic rays are different for different latitudes, height above sea-level, and with sun activity: on top of a mountain, the radiation dose is higher than on the ground. Also rocks and beach sand are more radioactive than other parts of the earth. Radioactive substances affects our food and drink, olives and brazil nuts are two food items that receive more radioactivity in comparison to others. There are many industries that produce and release radioactivity into the environment, this is especially the case with coal-burning plants, and to some extent, the fertiliser, mining and building industries. Other sources of radiation exposure are: older luminescent clocks and watches, compasses, exit signs, certain paints and pigments, dental porcelain, fire alarms, smoke detectors, television sets, normal operations of the nuclear power industry, and the use of radionuclides in industry, agriculture and the environment. Still with so many sources, the human race has continued to survive in this radioactive environment.

It's next to impossible to avoid the sources of natural radiation in our everyday life but we can take precautions to maintain distance with the local sources of radiation and also use distance, time and radiation shielding to protect ourselves. The less contact we have with such sources the lesser will be the dosage, however if it is necessary to use a source then it is mandatory one minimises the time spent near it, and in case of the source emitting strong radiation it is a must that one uses adequate shielding between the source and themselves.

The effect of radiation on the body

Ionising radiation does not accumulate in our body, but science proves that the radiation effects are evident from exposure to large amounts of radiation, as in sunburns from too much exposure to strong sunlight. Radiation carries energy that has a damaging effect on the living cells of living things and can either kill them or change their structure and function to inhibit correct functioning but this would take large doses to kill a good number of cells to cause death. Radiation dose would have to be several thousand times bigger than the dose received annually from the environment to cause death. Death would occur if the person were exposed more over a year. For example, exposure to sunlight over a year gives one a suntan, but one-day exposure of sunbaking could cause death by sunstroke.

Over a period of time, the body has the ability to repair small damage caused by radiation, but small dose can become more serious. There are two kinds of radiation damage: damage to any of the cells of our body, putting one at risk, and can even damage our reproductive cells putting future generations at risk. There are many different somatic effects but the long-term effect of radiation is caused by cancer. High exposure to radiation puts a person at a 40:1000000 chance of getting a cancer from a dose of radiation equal to one year of natural background. This means that lifetime dose of natural background gives one a 1:500 chance of dying from cancer.

Ionizing Radiation

Radiation is defined as the movement of energy in free space. Radioactivity is the activity of some unstable elements to decay and release radiation. Ionizing radiation contains enough energy to release electrons from atoms causing certain chemical properties of the substance it interacts with to change. Ionizing radiation is found in alpha particles, beta particles, gamma rays, x-rays and cosmic rays.

In chemistry it is known that when a nuclide decays, the left over substance will never possess the same chemical element as the original element had. After a certain point, the decay product will not be able to decay further due to stability. But if the decay product is still unstable it can undergo another radioactive decay later on. This is called half-life, which is defined as the time taken for half of a given amount of a nuclide to undergone radioactive decay.

Contamination

If contact is made with radioactive substances, it leads to contamination and the spread of radioactive material, however it is also true that simply contact with radioactive material will not make non-active substances radioactive.

Materials become 'radioactive' when they are contaminated by radioactive material by keeping them in close contact with such substances. An example of this is when a patient irradiated in the beam of an X-ray machine does not come out of the x-ray room being radioactive. However, a worker in the same room, in close contact with radioactive dust may have clothes or skin that has been contaminated or in the danger of inhaling radioactive material. This is why the person needs to undergo decontamination to lessen his radiation inhalation and consequently protect others from radiation.

The risks involved in radiation have been studied in depth by the study of groups of people exposed to known amounts of radiation using their own personal experiences, such as, atomic bomb survivors or radiotherapy patients, and also by the study of biological and cellular experiments. Radiation can cause two sorts of harmful effects on health because of radiation damage to tissues.

Stochastic Effects

These effects simply increase the risk of cancers and hereditary diseases over many years or decades after the first radiation dose. The risk is primarily proportional to the dose. To illustrate this, the best case is of radioiodine, which causes radiation exposure in a particular pattern of cancer in children its papillary thyroid carcinoma, which is very different from the natural incidence pattern. Despite the information available, the truth is that cancers caused by radiation cannot be differentiated from those caused by natural means.

The long-term cancer risk is estimated to be 5% per Sievert of whole body effective dose. This means that an additional radiation dose of 5 mSv would add an additional 0.025% to a person's 25% risk of dying from cancer. This would make their total cancer death risk 25.025%. Risk factors for non-fatal cancer and hereditary effects have also been estimated and are used for the purposes of radiological protection. Overall the risks of hereditary effects are judged to be substantially less than those of cancer. [LONDON HEALTH OBSERVATORY - Health In London, published: 18 November 2003]

Deterministic Effects

These effects take place when a threshold dose is reached but they really show the effects when very high doses of radiation are taken causing radiation sickness and radiation burns. The symptoms start after exposure and the greater the radiation dose is, the more severe the symptoms are.

Symptom Whole Body or Localized Exposure Minimum Dose for Detection

Detectable Chromosome Damage Without Symptoms Whole Body 0.1 Gy

Radiation Sickness Whole Body 1 Gy

Death From Radiation Sickness Whole Body 3 Gy (without medical treatment) & 5 Gy (with medical treatment)

Skin Reddening Localized 5 Gy

Skin Burn Localised 10 Gy

Source: LONDON HEALTH OBSERVATORY - Health In London, published: 18 November 2003]

Other than direct effects on the body, psychological effects may also take place in the person exposed to severe radiation and it has nothing to do with the radiation dose. The causes can be due to the way an incident is taken care of affecting the person's psychological side in an incident.

Radiation Exposure

Monitoring Radiation Exposure number of different organizations are making wide environmental measurements around the world, including local authorities and Government regulatory bodies. They research includes air measurements to look for radioactive plumes and regular monitoring of ionizing radiation in food crops as contained in the FSA report on radioactivity in food and the environment under Food standards.

Industries using radioactive materials are strictly monitored by the HSE, Nuclear Installations Inspectorate and, in also by the local authorities. Workers at risk of high exposure to radiation are required to undergo personal monitoring of radiation dose. The Central Index of Dose Information is the Health & Safety Executive's national database of occupational exposures to ionizing radiation. Radioactive sources and discharges into the environment have to be allowed under the Radioactive Substances Act (1993) by the Environment Agency. Heath and safety bodies from the department of health take care of and control medical radiation in the patient exposed. Businesses using radioactive resources must have a 'radiation protection adviser' such as a physicist, who keeps a check on the equipment and procedures.

Radiation Accidents

On an average, there is one major radiation accident every year in some part of the world. What is more common in England is accidents associated with lost source's. Lost sources are found in the scrap metal industry. Scrap metal yards have radiation monitors to detect any unknown radiation in the delivery received.

The nuclear industry and many other resources of radioactive sources are used in an enormous range of industrial processes such as, industrial radiography, thickness gauges, smoke alarms, medical diagnosis and treatment. This is why the number of accidents related to radiation is relatively high in the UK. The UK National Arrangements for Incidents involving Radioactivity scheme, employs a system that sends a response to the police in the UK if they suspect an uncontrolled radiation source.

Types Of Radiation Accident

There are 4 types of possible accident.

Criticality accidents. This is where a nuclear chain reaction occurs when not intended and radiation is released to the environment. An example is the accident in Tokai-Mura, Japan in 1999. A mixture of enriched uranium in nitric acid, which exceeded the critical mass, was created by mistake and a nuclear chain reaction occurred in a research laboratory giving very large doses to two people. A detonated nuclear weapon spreads fission products over a wide area because of a nuclear chain reaction.

Reactor accidents. A working reactor allows a nuclear chain reaction to occur in controlled circumstances. If the structure that contains the reactor is breached, or the nuclear reaction goes out of control, then fission products can be released into the environment. The accident at Chernobyl in 1986 is the best recent example.

Fires dispersing a plume of radioactive material. Here there is no nuclear chain reaction, but a plume disperses the radioactivity from a fire. If a nuclear weapon were involved in an accidental fire or conventional explosion, then plutonium from the weapon would disperse in this way. This happened in Palomares, Spain in 1966 when a B52 plane, carrying nuclear missiles crashed. This is not the same as detonation of the weapon.

Lost sources. The most harmful known lost source accident to date occurred in Goiania, Brazil in 1987. A radiotherapy source was broken open and radioactivity scattered widely within a city by hand-to-hand contact and cross contamination of the environment. Thousands of people were contaminated.

Source: LONDON HEALTH OBSERVATORY - Health In London, published: 18 November 2003]

Environmental health effects are similar on workers in the industry and public from ionizing radiation and perhaps from air pollution. Ionizing radiation has been under the limelight after the testing of nuclear weapons. This has been able to create compelling awareness in the nuclear power industry concerning radiation hazards. Radioactivity is measurable and its effects are understood better than those of other hazards with delayed effects, such as, all chemical cancer-inducing substances. Radiation is classified as a weak carcinogen

The food industry uses radiation

The food industry too uses radiation in the production, quality assurance, and sterilization of products. Radiation is increasingly used for the production of synthetic materials and natural rubber products. The radiation is used for polymerization without the bad side effects of heat processing.

Radiation is also used to preserve cold pasteurize food and sterilize medical products. This is the most cheapest way to destroy bacteria and viruses in products produced for human consumption for people with not so healthy immune systems.

Radiation has many uses, but it should be used cautiously to prevent the calamities that go hand in hand with its usage in industry and elsewhere.