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Ultraviolet Radiation

Ultraviolet Radiation

UV-radiation (also referred to as UV-light) is near to the blue wavelengths of visible light. If the visible light spreads on wavelengths 400-780 nm (nanometres), then UV-light is below 400 nm (click on the image).

Ultraviolet light is classified into three: UVA (315-400nm), UVB (280-315) and UVC (100-280nm). UVA light can be found, to a small extent, in the composition of light emitted by ordinary lamps.

Even though people cannot see the ultraviolet light, people do see fluorescent materials glowing under UV-light in darker rooms (e.g. safety features on banknotes).

Where does UV-Radiation Appear?

Outdoor Work

People mostly come in contact with UV-radiation during outdoor work. The strength of UV-radiation depends on the season and ozone layer thickness.

Most of the UVA light emitted by the Sun reaches the Earth, the emitted UVB light, however, in a notably smaller intensity. UVC light is absorbed completely in the upper layers of Earth atmosphere and never reaches the ground. Therefore, humans have developed a certain immunity against UVA and UVB radiations.

Illustration. Widespread exposure to UV-radiation (UVA and UVB) occurs outdoors. When working out for an extended period, care must be taken of skin and eyes’ health (click on the image to enlarge).

Arc Welding

Arc welding is one of the most widespread sources of artificial UV-radiation, and the radiation level is very high. The acute effect on the eyes and skin can appear during 3-10 minutes, standing in a few metres’ radius. Therefore, wearing eye and skin protection is mandatory.

Industrial UV-Lamps

UV-lamps are used in several industrial processes: hardening glue, plastic or paint. The construction of such lamps is usually already equipped with proper shields to protect the employees from radiation, but exposure to radiation is still possible in the case of emergencies or when neglecting safety measures.

“Blacklight” UV-Lamps

Weak intensity UV-lamps could be used when checking banknotes and documents, ingredients of powders; for interior decoration reasons in nightclubs, and elsewhere. Certain materials will glow when in such light. These lamps are not dangerous, except in some forms of skin hypersensitivity.

Medical UV-Lamps

For diagnostic or treatment purposes, UV-light is very widespread in medicine. Certain skin damages and illnesses appear more clearly in UV-light.

UV-light therapy is used for treating psoriasis, eczema, nevus’s and other skin problems.

Personnel of both therapeutic and diagnostic institutions must be well-trained to choose the ultimate dose of UV-radiation to use.

Antibacterial UVC-Lamps

Antibacterial (germicidal) UV-lamps are considered to be one of the most effective means of sterilization. They glow on UVC wavelengths and extinguish micro-organisms in the air, on work surfaces and instruments. UVC lamps are mostly used in hospitals, but also in microbiology laboratories. It is necessary that the placement of lamps, work procedures and the use of personal protective gear guarantees the safety of employees.

Solariums

Solariums used for artificial tanning mostly work on UVA wavelengths, but do include UVB radiation. Some newer models have been constructed to emit the more intense UVB light.

Visiting solariums on a regular basis could considerably increase the yearly UV-radiation dose of a person. Eye protection is requirement both for solarium users and personnel.

Compact Fluorescent Light Bulbs

Tests have shown that smaller doses of UV-radiation (in addition to UVA also UVB and a little UVC) can also be emitted by some compact fluorescent light bulbs. If such light bulbs are in the visual field and close, their UVB and UVC content could trigger snow blindness. But in general, compact fluorescent light bulbs are safe as most models filter the UVB and UVC out.

Health Effect

UVB light makes the skin produce vitamin D3 that, together with calcium, plays an important role in the skeletal and musculature health. However, the dose of UVB light required to achieve the aforementioned effect depends on:

  • the amount of vitamin D in the person’s menu,
  • the skin type,
  • the use of protective gear (clothes),
  • geographical latitude,
  • time (UV is most intense mid-day) and season (UV is most intense      mid-summer).

People will sense that UV-radiation has caused damage only after the formation of harmful consequences.

The harmful effect of the UV-radiation can be acute (sudden and instant), long-term following the acute dose and long-term following the chronic contact (regularly receives more than the organism can fully recover from).

People only come in contact with UVC-radiation emitted from artificial sources – such as antibacterial lamps. UVB-radiation is believed to be the most harmful UV radiation to humans, as excessive doses can damage skin and eyes.

Skin

The small dose of UVB-radiation that reaches the Earth through the atmosphere causes sunburn and other biological effects.

Even though the UVA-radiation penetrates the deepest through skin, it is biologically less damaging than UVB and UVC.

Sunburn or skin burn is a sign of short-term excessive contact with UV-radiation, whereas the premature aging of skin and skin cancer are signs of chronic UV-radiation overdose. Premature aging occurs when the skin loses the elasticity due to large doses of UVA and wrinkles up.

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

Eyes

When the sunlight (including the UV-radiation) reaches the eye directly or reflects from some surface, then the pupil design, closing of eyes and squinting protect the eyes from excessive light. But this reaction is only triggered by visible light, not UV light – thus, when coming into contact with only UV light, the same protective reaction does not follow and a risk of UV damage emerges.

UVB-radiation is thought to intensify cataract (grey cataract), which is the main cause of turning bling in the world. According to WHO, 20% of cataract cases could be related to excessive contact with UV light.

Photo keratitis or corneal flash burn and photo conjunctivitis are inflammatory reactions that cause pain in the eyes and temporary blurred vision. They do not seem to have a persistent effect on eyes and sight, and the problems fade.

Snow blindness is one of the most violent forms of photo keratitis. It appears in employees who work outdoors and come into contact with higher levels of UV-radiation – in higher areas due to surface reflection. For example, snow can reflect up to 80% of UV-radiation. In most cases, the damaged eyeball cells recover within a few days and eyesight returns.

Scientific research has shown that certain types of eye cancer could also be related to lifelong contact with sunlight.

Similarly to other risk factors of the working environment, the UV-radiation influence on a person depends on the duration and intensity of the exposure. It is also important how is the employee protected against the UV-radiation in the working environment or process – are safety glasses and clothes worn.

Certain types of medicaments, such as antibiotics, birth control pills, benzoyl peroxide products and certain cosmetics’ could increase the skin’s sensitivity against UV-radiation.

In the case of UV-radiation, like in the case of other optical radiations (infrared and laser radiation), the main risk groups are considered to be minors and pregnant women. Also, the employee’s health check results must also be taken into account: for example, an employee might have photo sensitivity (their skin is extremely sensitive to ultraviolet). If a person has photo sensitivity, only a minimum (some minutes) exposure to the Sun’s UV light is enough to trigger the allergic reaction (skin rash or sunburn)

When assessing the risk emanating from UV-radiation in a working environment, the UV-sensible chemicals and the concurrence of these two factors must also be taken into consideration. For example, glue or plastic which hardens in UV-light could damage the employees’ health in certain situations.

UV Type

In the Eye

On Skin

UVA

Photo keratitis

Photo conjunctivitis

Glaucoma

Light-induced retina damage

Erythema

Elastosis (photo aging)

Immediate darkening of the pigment

Skin cancer

UVB

Photo keratitis

Photo conjunctivitis

Glaucoma

Erythema

Elastosis (photo aging)

Skin cancer

UVC

Photo keratitis

Photo conjunctivitis

Erythema

Skin cancer

Prevention

The employer must ascertain the sources of UV-radiation in the working environment. If any are present, their radiation level must be evaluated or measured and, if required, measures applied to limit the radiation to the marginal rate. The regular sources of light are not treated as risk factors.

Usually, devices emitting UV-radiation are equipped with protective shields and other safety means, which decrease the employee’s contact with UV-radiation. Therefore, it is important not to illegally remove such protective devices.

Human exposure to UV-radiation can mostly be decreased with proper clothes and personal protective gear, including safety glasses, protective mask with a radiation filter, gloves, etc. Protecting the employee with only personal protective gear might not suffice – if possible, then the radiation risk must be eliminated or decreased to the minimum possible level in its’ place of origination.

The employer must inform all employees about all hazard factors and demand the use of personal protective gear; also, allow breaks for resting eyes.

Measuring

Ultraviolet radiation is measured with chemical or physical detectors, which usually have several filters to detect the proportion of UV components (UVA, UVB, UVC).

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