Radiation Types, Effects, Hazards & Control Measures
Radiation is a type of energy that travels through the air and can be absorbed by living things. It comprises tiny particles called photons, released when an atom decays or becomes unstable. Radiation can harm living things but can also be used for beneficial purposes, such as in medical imaging and cancer treatment.
There are two main types of radiation: ionizing and non-ionizing. Ionizing radiation has enough energy to remove electrons from atoms, which can damage cells and lead to cancer. Non-ionizing radiation does not have enough energy to cause this damage, but it can still be harmful if it is intense enough or if the body absorbs it over a long period.
Radiation is all around us, but it is not always dangerous. The sun emits ultraviolet radiation that can cause sunburn, but it also gives us vitamin D and helps us stay warm. Cell phones emit non-ionizing radiation, but their amount is very small and is not known to be harmful.
There are some situations where radiation can be dangerous, such as when someone is exposed to a large amount of radiation all at once (known as acute exposure), or when someone is exposed to lower levels of radiation over a long period (known as chronic exposure). Acute exposure can occur during a nuclear accident, while chronic exposure can occur from living near a nuclear power plant or working with radioactive materials. This blog post will discuss the types of radiation, its effects, hazards and the control measures associated with radiation.
Types Of Radiations & Their Applications
There are three types of radiations: alpha, beta, and gamma. Each has unique properties and uses.
Alpha radiation is the least penetrating of the three types of radiation. It comprises two protons and two neutrons bound together into a particle identical to a helium nucleus. Alpha particles are emitted from the nuclei of some radioactive atoms as they decay.
Beta radiation is more penetrating than alpha radiation, but not as much as gamma radiation. It is made up of either an electron or a positron (the antimatter counterpart of an electron). Beta particles are emitted from the nuclei of some radioactive atoms as they decay.
Gamma radiation is the most penetrating of the three types of radiation. It is a form of electromagnetic radiation, like X-rays. Gamma rays are emitted from the nuclei of some radioactive atoms as they decay.
There are many uses for radiation, both in medicine and industry. Radioactive isotopes are used in medical procedures such as PET scans and cancer treatments. They are also used in industrial processes like smoke detectors and radiotherapy.
Alpha radiation is used in smoke detectors. The alpha particles emitted by a radioactive isotope are detected by a sensitive detector. When smoke enters the detector, it absorbs some alpha particles, which triggers an alarm.
Beta radiation is used in cancer treatment. Beta particles can be directed at cancerous tissue, where they destroy the DNA and cause the cancer cells to die.
Gamma radiation is used in PET scans. A PET scan uses gamma rays to create images of the inside of the body. The gamma rays are emitted by a radioactive isotope and detected by a special camera.
Radiation can also be used for research purposes. For example, scientists use particle accelerators to study the properties of subatomic particles. Radiation is a powerful tool that can be used for both good and bad purposes. It is important to understand the risks and benefits of radiation before using it.
Ionising radiation is emitted from radioactive materials, either directly ionising alpha and beta particles or indirectly ionising X-rays, gamma rays, or neutrons. It has a high energy potential and an ability to penetrate, ionise and damage body tissue and organs.
All matter consists of atoms, a nucleus containing protons and neutrons, and orbiting electrons. The number of protons within the atom defines the element – for example, hydrogen has 1 proton, and lead has 82 protons. Some atoms are unstable and will change into atoms of another element, emitting ionising radiation. The change is called radioactive decay, and the ionising radiations most commonly emitted are alpha and beta particles and gamma rays. X-rays are produced by bombarding a metal target with electrons at very high speeds using high-voltage electrical discharge equipment. Neutrons are released by nuclear fission and are not normally found in manufacturing processes.
- Alpha particles consist of two protons and two neutrons and have a positive charge. They have little power to penetrate the skin and can be stopped using flimsy material, such as paper. Their main route into the body is ingestion.
- Beta particles are high-speed electrons whose penetration power depends on their speed, but penetration is usually restricted to 2 cm of skin and tissue. They can be stopped using aluminium foil. There are normally two routes of entry into the body – inhalation and ingestion.
- Like X-rays, Gamma rays are electromagnetic radiation and have far greater penetrating power than alpha or beta particles. They are produced from nuclear reactions and can pass through the body.
The two most common measures of radiation are the Becquerel (Bq), which measures the activity of a radioactive substance per second, and the Sievert (Sv), which measures the biological effects of the radiation – normally measured in milliSieverts (mSv).
Thus, the Becquerel (Bq) measures the amount of radiation in a given environment, and the milliSievert (mSv) measures the ionising radiation dose received by a person. Ionising radiation occurs naturally from man-made processes, and about 87% of all radiation exposure is from natural sources.
Harmful Effects Of Ionising Radiation
Ionising radiation attacks the body’s cells by producing chemical changes in the cell DNA by ionising it (thus producing free radicals), which leads to abnormal cell growth. The effects of these ionising attacks depend on the following factors:
- The size of the dose – the higher the dose then, the more profound will be the effect;
- The area or extent of the exposure of the body – the effects may be far less severe if only a part of the body (e.g. an arm) receives the dose;
- The duration of the exposure – prolonged exposure to a low dose is likely more harmful than a short exposure to the same quantity of radiation.
Acute exposure can depend on the dose size, blood cell changes, nausea and vomiting, skin burns and blistering, collapse, and death. Chronic exposure can lead to anemia, leukaemia and other forms of cancer. It is also known that ionising radiation can have an adverse effect on the function of human reproductive organs and processes. Increases in the cases of sterility, stillbirths and malformed foetuses have also been observed.
The health effects of ionising radiation may be summarised into two groups – somatic results, which refer to cell damage in the person exposed to the radiation dose and genetic influences, which refer to the damage done to any future children of the irradiated person.
Sources Of Ionising Radiation
The principal workplaces that could have ionising radiation are the nuclear industry, medical centres (hospitals and research centres) and educational centres. Radioactive processes are used for the treatment of cancers, and radioactive isotopes are used for many different types of scientific research. X-rays are used extensively in hospitals, but they are also used in the industry for non-destructive testing (e.g. crack detection in welds). Smoke detectors, used in most workplaces, also use ionising radiations.
Ionising radiations can also occur naturally – the best example is radon, a radioactive gas that occurs mainly at or near granite outcrops where there is a presence of uranium. It is particularly prevalent in Devon and Cornwall. The gas enters buildings normally from the substructure through cracks in flooring or around service inlets.
The Ionising Radiations Regulations have set two action levels above which remedial action, such as fitting sumps and extraction fans, has to be taken to lower the radon level in the building. The first action level is 400 Bq/m3 in workplaces and 200 Bq/m3 in domestic properties. At levels above 1000 Bq/m3, remedial action should be taken within one year. The average background radiation in the UK is 2.4 mSv per year. Background radiation levels are much higher worldwide – 260 mSv have been recorded in Iran.
About half of the background radiation in the UK is caused by radon. Radon gas is responsible for 5% of lung cancer cases. Radon is not generally a problem unless it can accumulate in confined spaces such as basements, cellars or lift shafts. An impermeable membrane beneath the floor can be laid to prevent the gas from entering the building through the floor. This latter treatment usually is only suitable for new buildings but does cost less than 10% of the cost of a sump and has no running costs. There are now government-defined ‘radon-affected areas’ throughout the UK, so checks should be made if underground spaces in buildings are to be used. About 14% of exposures to ionising radiation are due to medical exposures during diagnostic or treatment processes.
The hazards are categorised as either stochastic or non-stochastic. The principal stochastic hazard is cancer in various forms. The main nonstochastic effects include radiation burns, sickness, cataracts and damage to unborn children.
Personal radiation exposure can be measured using a film badge, which the employee wears over a fixed time interval. The badge contains a photographic film developed after the interval, and an estimate of radiation exposure is made. A similar device, known as a radiation dose meter or detector, can be positioned on a shelf in the workplace for three months to measure the mean value of radiation levels. Instantaneous radiation values can be obtained from portable hand-held instruments, known as Geiger counters, which continuously sample the air for radiation levels. Similar devices are available to measure radon levels.
Non-ionising radiation includes ultraviolet, visible light (lasers that focus or concentrate visible light), infrared and microwave radiation. As the wavelength is relatively long, the energy present is too low to ionise atoms which make up matter. The action of non-ionising radiation is to heat cells rather than change their chemical composition.
The Control of Artificial Optical Radiation at Work Regulations govern non-ionising radiation. The Personal Protective Equipment at Work Regulations is also relevant since skin or eye tissue burning is the most significant hazard.
Ultraviolet radiation (UV) occurs with sunlight and with electric arc welding. In both cases, the skin and the eyes are at risk from the effect of burning. The skin will burn (as in sunburn), and repeated exposure can lead to skin cancer. Skin exposed to strong sunlight should be protected by clothing or sun creams. This problem has become more familiar with the reduction in the ozone layer (which filters out much ultraviolet light). The eyes can be affected by conjunctivitis, which feels like grit in the eye, and is called various names depending on the activity causing the problem. Arc welders call it ‘arc eye’ or ‘welder’s eye’ and skiers’ snow blindness. Cataracts caused by the action of ultraviolet radiation on the eye lens are another possible outcome of exposure.
The most dangerous form of skin cancer, malignant melanoma, has increased by over 40% over the last ten years, making it cancer with the fastest rising number of cases in the UK. Outdoor workers that could be at risk include farm or construction workers, market gardeners, outdoor activity workers and some public service workers. Those who are particularly at risk have:
- fair or freckled skin that does not tan or goes red or burns before it tans;
- red or fair hair and light-coloured eyes;
- a large number of moles.
Employers must be aware of their employees’ risks when working outside without adequate sun protection. With growing concern following the rise in skin cancers, the HSE has suggested the following hierarchy of controls for outdoor working:
- relocate some jobs inside a building or to a shady location;
- undertake some outdoor work earlier or later in the day;
- provide personal protection such as: wearing long sleeve shirts or loose clothing with a close weave; wearing hats with a wide brim; using a high factor sunscreen of at least SPF15 on any exposed skin;
- provide suitable education and training for outdoor workers;
- Provide suitable information and supervision to instigate safe systems of work that protect workers from the sun.
UV radiation has beneficial effects, such as accumulating vitamin D and strengthening bones.
Where UV interlocutors are used, generally in kitchens, to control flying insects, the correct emitting labels must be fitted and not ones that, for example, are used to sterilise surgical instruments, as has happened on one occasion.
Lasers use visible light and light from the invisible wavelength spectrum (infrared and ultraviolet). As the word laser implies, they produce ‘light amplification by stimulated e mission of r radiation. This light is highly concentrated and does not diverge or weaken with distance. The output is directly related to the chemical composition of the medium used within the particular laser. The output beam may be pulsating or continuous depending on the laser’s task. Lasers have extensive applications, including bar code reading at a supermarket checkout, metal cutting, and welding, and accurate measurement of distances and elevations required in land and mine surveying. They are also extensively used in surgery for cataract treatment and the sealing of blood vessels.
The International Electrotechnical Commission (IEC) and the American National Standards Institute (ANSI) have defined seven classes of laser (1, 1M, 2, 2M, 3R, 3B and 4) in ascending size of power output. Classes 1, 1M, 2, and 2M are relatively low hazards and only emit light in the visible band. Direct eye contact must be avoided in classes 3R, 3B and 4. These are more hazardous than classes 1 and 2; a laser safety officer appointment is recommended. A Class 4 laser can burn the skin and cause permanent eye damage due to direct, diffuse or indirect exposure to the beam. Such Class 4 lasers can ignite combustible materials and are a fire risk. All lasers should carry information about their class and any precautions required.
The main hazards associated with lasers are eye and skin burns, toxic fumes, electricity, and fire. The vast majority of accidents with lasers affect the eyes. Retinal damage is the most common and irreversible. Cataract development and various forms of conjunctivitis can also result from laser accidents. Skin burning and reddening (erythema) are less common and are reversible.
Infrared radiation is generated by fires and hot substances and can cause eye and skin damage similar to that of ultraviolet radiation. It is a problem for firefighters and those working in foundries or near furnaces. Eye and skin protection are essential.
Microwaves are used extensively in cookers and mobile telephones, and there are ongoing concerns about associated health hazards (and several inquiries are currently underway). The severity of any hazard is proportional to the power of the microwaves. The principal hazard is heating body cells, particularly those with little or no blood supply, to dissipate the heat. This means that tissues such as the eye lens are most at risk from injury. However, it must be stressed that the chances are higher for items such as cookers than for low-powered devices such as mobile phones. The measurement of non-ionising radiation typically involves the determination of the power output being received by the worker. Specialists in the field best perform such surveys, as interpreting the survey results requires considerable technical knowledge.
Radiation Protection Strategies
Protection is obtained by applying shielding, time, and distance individually or, more commonly, using a mixture of all three.
Shielding is the best method because it is an ‘engineered’ solution. It involves placing a physical shield, such as a layer of lead, steel and concrete, between the worker and the radioactive source. The thicker the shield, the more effective it is.
Time involves using the reduced time exposure principle and thus reduces the accumulated dose.
Distance works on the principle that the effect of radiation reduces as the distance between the worker and the source increases.
Other measures include the following:
- effective emergency arrangements;
- training of employees;
- the prohibition of eating, drinking and smoking adjacent to exposed areas;
- a high standard of personal cleanliness and first-aid arrangements;
- strict adherence to personal protective equipment arrangements, which may include complete body protection and respiratory protection equipment;
- procedures to deal with spillages and other accidents;
- prominent signs and information regarding the radiation hazards;
- medical surveillance of employees
The Ionising Radiations Regulations specify a range of precautions that must be taken, including the appointment of a Radiation Protection Supervisor as the competent person and a Radiation Protection Adviser.
The employer must appoint the Radiation Protection Supervisor to advise on the necessary measures for compliance with the Regulations and its Approved Code of Practice. The person appointed, usually, an employee must be competent to supervise the arrangements in place and have received relevant training.
The employer appoints the Radiation Protection Adviser to advise the Radiation Protection Supervisor and employer on any aspect of working with ionising radiation, including the appointment of the Radiation Protection Supervisor. The Radiation Protection Adviser is often an employee of a national organisation with expertise in ionising radiation. A Radiation Protection Adviser is not needed when the only work with ionising radiation is specified in Schedule 1 of the Regulations.
For ultraviolet and infrared radiation, eye protection in the form of goggles or a visor is most important, particularly when undertaking arc welding or furnace work. Skin protection is also likely necessary for the hands, arms and neck in the form of gloves, sleeves, and a collar. For construction and other outdoor workers, protection from sunlight is essential, particularly for the head and nose. Sun creams should also be used.
Engineering controls such as fixed shielding and non-reflecting surfaces around the workstation are recommended for laser operations. For lasers in the higher class numbers, special eye protection is recommended. A risk assessment should be undertaken before a laser is used.
Engineering controls are primarily used for protection against microwaves. Typical rules include enclosing the whole microwave system in a metal surround and using an interlocking device that will not allow the system to operate unless the door is closed.
Intense sources of artificial light in the workplace, particularly from UV radiation and powerful lasers, can harm the eyes and skin of workers and need to be properly managed. The Control of Artificial Optical Radiation at Work Regulations came into force in 2010 and implemented the Physical Agents (Artificial Optical Radiation) Directive (2006/25/ EC). The Regulations aim to ensure that standards are set so that all workers are protected from harm arising from exposure to hazardous sources of artificial light. As with the previous Noise and Vibration Regulations, it contains provisions on risk assessment, control of exposure, health surveillance and information, instruction, and training. The Regulations are based on the limit values incorporated in the guidelines issued by the International Commission on Non-Ionising Radiation Protection (ICNIRP).
Workers should be protected from hazardous sources of light in the workplace to ensure that the eyes and skin of workers are adequately protected from intense sources of light at work that can damage the eyes and skin. Such light sources include ultraviolet, visible, and infrared radiation produced by artificial sources, such as lasers and welding arcs. Examples of such hazardous light sources include:
- welding work (both arc and oxy-fuel) and plasma cutting causing mainly eye damage;
- furnaces and foundries causing eye and skin damage;
- printing involving the UV curing of inks causing mainly skin damage;
- motor vehicle repairs involving the UV curing of paints causing mainly skin damage;
- medical and cosmetic treatments involving laser surgery, blue light, and UV therapies causing both eye and skin damage;
- all use of Class 3B and Class 4 lasers potentially causes permanent vision and skin damage.
The EMF Directive
Electric, magnetic, and electromagnetic fields (EMFs) are a form of non-ionizing radiation that arises whenever electrical energy is used. Electric charges generate an electric field, while a magnetic field occurs around an electric current. Electromagnetic fields are mutually produced by time-varying magnetic and electric fields. When electric fields act on conductive materials (such as the human body), they influence the distribution of electric charges at their surface, causing current to flow through the body to the ground. Magnetic fields induce circulating currents within the human body. The strength of these currents depends on the intensity of the outside magnetic field. These currents can stimulate nerves and muscles or cause other biological effects such as nausea if sufficiently large.
Common electromagnetic fields include work processes such as radiofrequency heating and welding, household electrical wiring and appliances; electrical motors; computer screens; telecommunications; transport and distribution of electricity, broadcasting, and security detection devices.
The EMF Directive covers a frequency spectrum from 0 to 300 GHz, including static magnetic fields and low-frequency electric and magnetic fields, through radio frequency and microwave frequencies.