Radiations

Ionising radiation

Radiations are classified according to their ability to cause damage to the body into ionising and non-ionising radiations.

Non-ionising radiation includes, for example, infrared radiation, radio and microwave waves, and ultraviolet radiation. Shortwave ultraviolet radiation can also be ionising, but it can be easily shielded, for example, by clothing and also the skin. Read more about these radiations in other sections of this website.

Ionizing radiation or radioactivity or radioactive decay characterises the particles or energy emitted from atoms. Such a substance is called radioactive material. Figuratively speaking, the radioactive substance can be compared to an open popcorn machine, from which particles are ejected chaotically in all directions. Unlike popcorn, however, the radioactive particles are tiny and high in energy. If these particles were to hit a human being, it would have an ionising effect on the atoms of living tissues, i.e. it could ‘damage’ those atoms.

Ionising radiation is a daily phenomenon for humans. It has accompanied mankind in its evolution and, according to some scientists, even contributed to human development. In addition to natural radiation sources, modern mankind has also been exposed to radioactivity from artificial sources.

The natural radiation dose mainly consists of radiation from soil and building materials, cosmic radiation, as well as radionuclides and radon entering the human body. The latter two account for about half of the natural radiation dose. In Estonia, the share of radon may be even higher in some places, based on areas with elevated radon presence. Radionuclides enter the body through food and water.

The cosmic radiation background can professionally be a major contributor to an employee's annual radiation dose. For example, at an altitude of 15 km where passenger planes fly, the radiation level is 10 Sv/h (micro sieverts per hour). However, at sea level the radiation level is 0.03 Sv/h (IAEA).

Table. Radioactive radiation is divided into three classes.

	alpha radiation	beta radiation	gamma radiation
Characterisation	Alpha particles have strong energy but do not last long. Cannot even penetrate paper. The skin also stops the alpha particle.	The beta particle is much smaller than the alpha particle and can penetrate much deeper into the materials and living tissues. It also has more energy and therefore a greater ability to do harm. The beta particle is stopped by, for example, aluminium paper, plastic, glass or a piece of wood.	Very high energy photons, which are the most penetrating radioactive radiation. A thick layer of dense substance (such as lead or steel) or large amount of soil or concrete is required for stopping.
Danger	Represents little danger when exposed externally. Represents greater danger if inhaled or swallowed. For example, radon (inhalation)	Represents danger     (1) taking in and     externally. May cause harmful ‘beta burns’ to the skin and damage the subcutaneous blood system. Normally, however, it does not penetrate deeper than the surface of the skin. Represents greater danger if inhaled or swallowed (e.g. food is contaminated).	Gamma radiation can severely damage the internal organs without having to be ingested. Represents a danger to the whole body both externally and internally. Can cause severe and irreversible damage to the body.
Safety	1) closed containers. Alpha radiation is usually trapped by clothing or the outer layers of the skin. Hygiene requirements and decontamination procedures must be followed to deal with alpha radiation in high-risk workplaces.	1) closed containers.     2) local shielding; and     3) monitoring of exposure time.     Hygiene requirements and decontamination procedures must be followed to deal with alpha radiation in high-risk workplaces.	1) going beyond the radiation source; 2) shielding; 3) minimisation of exposure time. Chemical protective clothing does not provide any protection against gamma radiation itself, but at the same time wearing respirators (filters) and protection clothing helps prevent radioactive materials from entering the body. Gamma radiation cannot be completely stopped by shielding – its intensity can only be reduced. The gamma shielding factor depends on the screen material and its thickness.

The main sources of radioactive radiation are, for example:

• medical X-rays,
• radioactive contamination from the testing of nuclear weapons in the atmosphere,
• release of radioactive emission from the nuclear industry into the environment,
• industrial gamma radiation,
• other sources, such as consumer goods.

 

In Estonia, occupational exposure to radioactivity can occur in two main cases:

• failure to observe accident or safety requirements during the handling and transport of radioactive waste,
• failure to meet the safety requirements when working with a radiation source.

In addition to the above, nuclear power plants located in neighbouring countries can also be considered as sources of risk, which in the event of an accident also pose a threat to the Estonian population (Loviisa in Finland and Sosnovõi Bor).

 

Health effects

Radioactivity can affect humans in two main ways: internally and externally. By acting on the outside of the body, the radiation comes from radioactive material that emits to the human body alpha, beta or gamma radiation. However, internal radiation occurs after exposure to a radioactively contaminated environment, when radionuclides released into the body by inhalation or ingestion continue their ‘radiation work’ inside the human body. For example, radionuclides can be deposited on the ground from the atmosphere and then enter the food chain or drinking water.

Figure. Entry of radioactively contaminated particles into the body

Figure. The average annual radiation dose comes from these sources (IAEA).

The energy released by radioactive decay is dangerous to biological tissues (humans). Radiation damages the genetic material inside the cell, which gives rise to the risk of tumours. The more radiation is received, the greater the damage to the body's cells. Genetic damage extends from generation to generation and poses a health risk to future generations.

A large amount of radiation is followed by severe symptoms within a few days and even death at a higher dose (if more than 1000 times the annual dose was obtained during the incident). Moderate radiation exposure may not have an immediate effect, but health problems can arise years later.

All people are receiving small doses of radiation from the environment on a daily basis, which, however, is not harmful to health.

The harmful effects of radiation exposure mainly depend on the dose and the time of exposure. The dose depends on the intensity of the radiation source, how close the person is to it and the degree to which the person is protected by personal protective equipment.

The following symptoms may occur after exposure to radioactivity:

• lesions on the skin from redness to burns;
• wounds and bleeding in the mucous membranes of the mouth, nose and digestive tract;
• nausea, vomiting, diarrhoea;
• hand tremors, seizures;
• headaches, weakness, heart palpitations;
• hair and other body hair loss;
• loss of appetite, apathy, depression (damaged hematopoietic system).

Pregnant women belong to a risk group because exposure to radioactivity may adversely affect foetal development. High doses of radiation can result in foetal death or severe damage. According to the ICRP, there is a direct link between a child's later intelligence and the radiation dose received during foetal life. There is also an increased risk of malignant tumours if a person was exposed to radioactive radiation before birth.

Infrared radiation

Infrared radiation is a natural part of a person's living and working environment, so people are regularly exposed to it. For example, when in the sun, the infrared part of the sun's radiation is sensed as the feeling of heat. Also, when heating a (stone) stove, infrared radiation emits from the heated stones. When two or more people are naked, they feel the heat (infrared) radiating from each other.

Many industrial processes require intense heat, which increases the exposure of workers involved in these processes to infrared radiation much higher than in other industries. Examples of such processes include firefighting, baking, glassblowing, drying, burning, welding, mould casting, smelting and other ironworks. Many industrial, medical and laboratory lasers also emit strong infrared radiation.

 

Table. Examples of occupational exposure to infrared radiation.

 

source	activities and exposed persons		exposure
sunlight	field workers: farmers, construction workers, seafarers, etc.		500 W/m²
electric filament lamps	ink and paint drying, conventional lighting		105–106 W/m²/sr
halogen filament lamps	drying, baking, heating, copying machines		50–200 W/m² (at a distance of 50 cm)
xenon arc lamps	printing processes, projection systems, searchlights, laboratory staff		107 W/m²/sr
iron smelting	melting furnace work		105 W/m²/sr
infrared lamps	industrial drying and heating		103–8x103 W/m²
infrared lamps for hospitals	incubators		100–300 W/m²

Infrared radiation (also infrared light) is beyond human vision, from 780 nanometres (the last red wavelengths a person is able to see). Humans are able to perceive with the eyes only a very small part (400–780 nm) of the entire electromagnetic spectrum, and this area is distinguished by colours: purple, blue, green, yellow, orange, red.

Infrared radiation is sometimes called heat radiation because we perceive some of its wavelengths as heat on our skin.

Infrared radiation is classified (according to ISO 20473) into three regions :

near infrared 0.78–3 m, middle infrared 3–50 m, far infrared 50–1000 m.

Figure. Location of infrared radiation in the electromagnetic spectrum

Health effects

Since optical radiation generally does not penetrate very deep into biological tissues, most attention should be paid to the eyes and skin. Exposure to infrared radiation usually requires dealing with the thermal effect.

Eyes

In general, the human eye is well protected from natural optical radiation, including solar radiation. This protection also extends to bright artificial lighting. Radiation mainly affects the retina of the eye, as the internal matter of the eye is translucent. However, the transparency of the lens of the eye may be reduced if you look directly at a source of bright near infrared radiation.

Eye lens damage occurs at wavelengths below 3 metres (bright near infrared and visible light). The longer the wavelength of the infrared radiation, the less it reaches the back of the eye. Middle and far infrared radiation, however, is mostly absorbed by the cornea of the eye. The absorption of long-wave infrared radiation in the cornea, in turn, can lead to an increased temperature in the eye. Intense far infrared radiation can cause corneal burns, similar to the skin. Such burns, however, are rare because they are preceded by a pain reaction. Heat-induced eye damage can, for example, be cataracts, which are more common in glassblowers than in other professions.

Infrared radiation does not reach very deep into the body. Therefore, intense infrared radiation mainly results in the local thermal effect and even burns. In particular, long-wave infrared radiation can cause high temperatures and burns to the skin of the exposed part of the body. As the skin is also able to dissipate heat, the time during which the adverse effects occur depends on the intensity and the time of exposure. For example, infrared radiation with a power of 10 kW/m² causes a pain response in five seconds; the power of 2 kW/m² in about 50 seconds. If the exposure lasts for a long time, the heat load on the body can be high, especially if the whole body is exposed to it (for example when working in front of an iron melting furnace). This can result in an unbalanced thermoregulatory mechanism in the body. The tolerance of such environments also depends on the employee's personal tolerance and the environmental conditions (humidity, air velocity). Without performing physical work, a person can tolerate 300 W/m² in an eight-hour working day, while with heavy physical work only 140 W/m².

Table. Organs sensitive to damage by infrared radiation

Infrared radiation type	in the eye	on the skin
IRA	retina	subcutaneous tissue
IRB	cornea	corium
IRC	cornea	stratum corneum

 

Prevention

Infrared radiation from commonly used lamps or most industrial equipment does not pose a risk to workers. However, in certain workplaces where special lamps, heaters and other sources of infrared radiation are used, the work process can be harmful to the health of workers.

The most effective protection against infrared radiation is full sealing of the radiation source. Attention should also be drawn to hot bridges that may originate from the source. In most cases, the thermal shielding of the radiation source brings the working environment into compliance with the limit values. In other cases, personal protective equipment must be used. Thermally shielding personal protective equipment includes:

• face shield or protective goggles,
• thermal suit,
• thermal gloves, thermal footwear and headgear.

In exceptional cases, where working conditions do not allow the above-mentioned protective measures to be taken, work organisation measures must be taken to protect workers. For example, workers' access to extremely hot work areas can be restricted. The input power of the heat source can also be reduced for the period during which workers must be in its vicinity. Reducing working hours, taking more breaks and working in shifts can also be used to minimise the exposure time of an employee. It must be taken into account that working in a hot environment causes heat stress in a person, which is why they need more rest time to recover.

When assessing the biological effects of infrared radiation, it is necessary to take into account the wavelength, intensity and exposure time of the radiation source by the worker. In particular, the limit values serve to provide protection against harmful thermal effects on the retina and cornea. The limit values also protect against the delayed adverse effects on the lens.

It is the employer's responsibility to identify the sources of infrared radiation in the working environment. If they occur, the level of radiation must be assessed or measured and, if necessary, measures taken to limit the radiation in accordance with the limit values. Conventional light sources in an establishment are not considered as risk factors.

The employer must inform employees of all risk factors and require the use of personal protective equipment, as well as allow breaks to rest the eyes.

 

Ultraviolet radiation

Ultraviolet radiation (also called ultraviolet light) is close to the blue wavelengths of visible light. If the visible light is at wavelengths 400–780 nm (nanometres), then the ultraviolet light is below 400 nm (also click on the picture).

Ultraviolet light is classified into three regions: UVA (315–400 nm), UVB (280–315 nm) and UVC (100–280 nm). Of these, UVA light is also present to some extent in the white light of commonly used lamps.

Although a person cannot see ultraviolet light, they can observe materials that glow under UV light in darker rooms (for example, a security label on banknotes).

 

Where is ultraviolet radiation present?

Field work

The main occupational exposure of people to UV radiation is during field work. The intensity of UV radiation depends on the season and the thickness of the ozone layer.

From the sun, it is mainly UVA light that reaches the earth, whereas UVB light reaches the earth at a much lower intensity. However, UVC light is completely absorbed in the upper layers of the Earth's atmosphere and therefore does not reach the earth. Therefore, a person is adapted to tolerate a certain amount of UVA and UVB radiation.

Figure. The most common exposures to UV radiation (UVA and UVB) occur in field work, where prolonged exposure requires skin and eye health protection.

Antibacterial (germicidal) UV lamps are considered to be one of the most effective sterilisation methods. They emit UVC wavelengths to kill airborne micro-organisms on work surfaces and instruments. UVC lamps are mainly used in hospitals, but also in microbiology laboratories. It is necessary that the placement of lamps, operating procedures and the use of personal protective equipment ensure the safety of workers.

Solariums

Solariums used for artificial tanning mainly emit UVA wavelengths, but also contain UVB radiation. Some newer models have also been introduced to produce more intense UVB radiation.

Regular use of a tanning bed can significantly increase a person's annual dose of UV radiation. Eye protection is necessary for both solarium users and the staff.

Energy-saving lamps

Studies have shown that smaller amounts of UV radiation (in addition to UVA, UVB and some UVC) may also be present in some energy-saving light bulbs. When such energy-saving light bulbs are in sight and a person is close to them, their UVB and UVC will induce snow blindness. In general, however, energy-saving bulbs do not pose a risk, as most models filter out UVB and UVC.

Health effects

Under the influence of UVB light, the skin produces vitamin D3, which together with calcium plays an important role in musculoskeletal health. However, the dose of UVB light required to achieve this effect depends on:

• the amount of vitamin D in a person's diet;
• their skin type;
• the use of protective equipment (clothing);
• the geographical latitude;
• the time of day (more intense UV at noon) and the season (more intense UV mid-summer).

A person can only become aware of the damage caused by UV radiation with their senses when the harmful consequences have occurred.

Adverse effects of UV radiation can be acute (i.e. sudden and immediate), long term after an acute dose, and long term after chronic exposure (regular doses higher than what the body can fully recover from).

Humans are only exposed to UVC radiation from artificial sources, such as antibacterial lamps. UVB radiation is considered to be the most dangerous UV radiation for humans, as excessive doses can damage the skin and eyes.

Skin

The small amount of UVB radiation that reaches the earth through the atmosphere causes, for example, sunburn and other biological effects.

Although UVA radiation reaches most deeply through the skin, it is not as biologically harmful as UVB and UVC.

Sunburn or skin burns are a sign of short-term overexposure to UV radiation, while premature skin ageing and skin cancer are a sign of a chronic overdose of UV radiation. Premature ageing occurs when large amounts of UVA cause the skin to lose its elasticity and wrinkle.

UV radiation also weakens the immune system, increasing the susceptibility to skin infections.

Eyes

If direct or reflected sunlight (including UV radiation) comes into contact with the eyes, the structure of the pupil, the closure of the eyes and the squinting reaction will take care to protect the eyes from excess light. However, this reaction is caused by visible light, not UV light – so when exposed to UV light alone, the same protective reaction does not follow and there is a risk of UV damage.

UVB radiation is thought to amplify cataracts, which are the leading cause of blindness in the world. The WHO estimates that 20% of cataract cases may be related to overexposure to UV light.

Photokeratitis, or light burning of the cornea, and photo conjunctivitis are inflammatory reactions that cause pain in the eyes and temporary blurring of vision. However, they do not seem to have a lasting effect on the eye and vision, and the problems surpass.

Snow blindness is one of the most acute forms of Photokeratitis. It occurs in workers who are exposed to higher levels of UV radiation outdoors – in higher areas due to ground reflections. For example, snow can reflect back up to 80% of UV radiation. In most cases, the damaged cells in the eyeball recover within a few days and vision is restored.

Research has shown that certain types of eye cancer may also be associated with lifelong exposure to sunlight.

As with other hazards in the working environment, the effects of exposure to UV radiation depend on the duration of exposure and the intensity of the radiation. The use of safety goggles and clothing also plays a role in how well the worker is protected from UV radiation in the working environment or work process.

Certain types of medication, such as antibiotics, birth control pills, benzoyl peroxide products, and some cosmetic products, can increase the skin's sensitivity to UV radiation.

In the case of UV radiation, as in the case of other optical radiation (infrared and laser radiation), minors and pregnant women in particular are considered to be at risk. The results of the employee's medical examination must also be taken into account: for example, if a person has photosensitivity (skin is hypersensitive to ultraviolet radiation). In the case of photosensitivity, even minimal (a few minutes) exposure to the sun's UV light is sufficient to cause an allergic reaction (skin rash or sunburn).

UV-sensitive chemicals and the combination of these two factors must also be taken into account when assessing the risk of UV radiation in the working environment. For example, glue or plastic that cures under UV light can damage a worker's health if certain circumstances arise.

UV type	In the eyes	On the skin
UVA	Photokeratitis Photo conjunctivitis Cataract Light induced retinal damage	Erythema Elastosis (photoaging) Immediate pigment darkening Skin cancer
UVB	Photokeratitis Photo conjunctivitis Cataract	Erythema Elastosis (photoaging) Skin cancer
UVC	Photokeratitis Photo conjunctivitis	Erythema Skin cancer

 

Prevention

It is the employer's responsibility to identify the sources of UV radiation in the working environment. If they occur, the level of radiation must be assessed or measured and, if necessary, measures taken to limit the radiation in accordance with the limit values. Conventional light sources in an establishment are not considered as risk factors.

Equipment that emits UV radiation is usually equipped with protective screens and other safety devices that reduce the worker's exposure to UV radiation. It is therefore important that these safety devices are not removed arbitrarily during operation.

Human exposure to UV radiation can primarily be reduced with work clothes and personal protective equipment, including goggles, a radiation shield, gloves, etc. Protecting the worker with personal protective equipment alone may not be sufficient; if possible, the radiation risk must be eliminated at source or reduced to a minimum.

The employer must inform employees of all risk factors and require the use of personal protective equipment, as well as allow breaks to rest the eyes.

Measurement

Ultraviolet radiation is measured with chemical or physical detectors, often with different filters to determine the ratios of UV components (UVA, UVB, UVC).

Laser radiation

Whether and to what extent the damage occurs depends on:

• the amount of energy absorbed and whether it was a pulsed laser,
• what focus the eye was in, and
• what area of the eye the laser beam hit.

When damage to health occurs due to a laser beam, vision suddenly disappears and a bright flash is visible for a moment. Sometimes there may be a crackling sound and the feeling of pain. Whether the damage is permanent or not depends on which point in the eye the laser beam hits. For example, damage to the edges of the retina may go unnoticed.

In the case of accidents with more powerful lasers, the eye damage may not be limited to the contact area of the laser point. The optic nerve connections and retina can be damaged and intraocular haemorrhage may occur.

The damage caused by the middle infrared laser is mainly thermal, i.e. caused by thermal radiation. As the middle-infrared radiation is absorbed by water, most of the laser radiation energy is absorbed before it reaches the back of the eye.

Skin damage

Laser-induced skin damage is usually limited to a small burn. In milder cases, there is only reddening of the skin, which heals quickly. Prolonged exposure may cause blisters, grade 3 burns and even charring of skin tissues.

Subcutaneous tissues are usually well protected from laser radiation. However, a continuous laser beam with a very high power (over several kilowatts) can penetrate the skin and damage subcutaneous tissues. However, if the safety rules are followed, the risk of such an accident is minimal.

Prevention

The majority of occupational accidents with lasers have occurred during experimental work in research laboratories. The main reason is non-compliance with safety requirements.

Accidents have also been caused by military laser rangefinders. The latter pose a threat both to the personnel handling them and to civilians within the range of several kilometres, as these are powerful lasers.

In the case of laser radiation, the safety of the eyes must be taken into account. Workers exposed to laser radiation must wear safety goggles. Even when wearing goggles, the laser should never be aimed at the eyes.

The general principles of safety are:

• thorough training of employees on all hazards and safe working methods;
• if the work process enables it, shield the laser beam completely from people;
• do not aim the laser beam at a person;
• the laser is used under supervision;
• storage and transport conditions must not damage the laser;
• specific safety requirements depending on the laser class;
• monitoring compliance with safety rules.

The most common means of protection against laser radiation are goggles. It is necessary to ensure that the glasses are selected to specifically block the wavelengths at which the laser is operating. Care must be taken to ensure that the goggles protect against all wavelengths generated by the laser. In the case of cheaper spectacles, it has been found that the specification that comes with them does not correspond to their actual protection range (wavelengths).

Strong ultraviolet radiation is also a side effect of the CO2 laser welding process. Therefore, the whole process should be completely separated if possible. If shielding is not possible, all persons present must wear personal protective equipment (protective clothing, mask).

class	wavelengths	characterisation	safety requirements	examples
1	ultraviolet, visible light, infrared	Low power lasers. Laser radiation does not pose a risk even during long exposures. also includes higher power lasers that work inside the enclosure and cannot escape.	Safety is guaranteed without special measures being taken	toys, laser printers, CD and DVD players
1M	ultraviolet, visible light, infrared up to 500 mW	power density exceeds class 1, but because the beam is scattered, only a small part of the laser’s total capacity could reach the eye	Avoid watching the beam is with optical aids (e.g. binoculars)	certain wireless data solutions
2	visible light up to 1mW	Low power lasers. A blink reflex of about 0.25 sec is found to be sufficient to protect the eye from damage. The laser can only be dangerous if it is aimed directly to the eye and the person looks at the laser beam intentionally.	In addition to the above, termination of beam, monitoring the path of movement of the beam	barcode readers certain directional lasers,
2M	visible light up to 500 mW	Has more power compared to class 2, but similarly to class 1M lasers the laser beam is scattered. The laser can only be dangerous if it is aimed directly to the eye and the person is viewing the laser beam intentionally or by means of an optical device concentrating the beam.	In addition, marking of the path of movement of the beam, removal of unnecessary reflections	construction levelling and directional lasers
3R	visible light up to 5mW, invisible light	The radiated power may exceed up to 5x the class 1 (invisible range) and class 2 (visible range). Although in direct contact with the naked eye the 3R class laser exceeds the limit value, but due to high safety margin, in practice there are no damages. However, in principle, in this case eye damage is still possible.	in addition to the above, looking at the beam is avoided	certain directional lasers and measuring lasers used in construction work
3B	up to 500mW	Radiated power exceeds the class 3R lasers. A direct or reflected laser beam is always dangerous to the eyes.	in addition to the above, security locks for the rooms where lasers are used, eye protection	Laboratory lasers for use in research institutions
4	Upper limit not established	Radiated power exceeds the class 3B lasers. The beam is so strong that it can instantly cause a burn to the skin. The eye can be damaged by reflection alone.	In addition to the above, skin protection, active and passive protective barriers in the case of powerful lasers	laser surgery, metal cutting, welding, show lasers

 

Measurement

It is important for the safety of lasers:

• how much energy is absorbed by biological tissues; and
• what wavelength is it (what type of laser).

When exposed to laser radiation, the energy density (J/m²) and power density (W/m²) of the laser beam falling on the surface of the eye and skin are primarily monitored.