About UV radiation

Ultraviolet radiation (UV) is electromagnetic waves with wavelengths shorter than visible light.

• UVA for wavelengths 400 – 315 nm
• UVB for wavelengths 315 – 280 nm
• UVC for wavelengths shorter than 280 nm

UVA (315-400 nm) radiation is used in lamps for technical purposes, in solarium etc., UVB (280-315 nm) and UVC (200-280 nm) radiation are within the range with the highest impact on bacteries. For inactivation and determination of bacteries wavelength under 300 nm is the most effective. The highest production of ozone is around 200 nm wavelength. If there is concentration on cleaning of microbiological contamination the best solution is to use wavelength between 200 - 300 nm. UV radiation arises when current flows between two electrodes in quartz tube filled with mercury vapor.

So called "black" light" is soft UV radiation within the range of wavelegths λ = 300 - 400 nm. This radiation is provided by some special light sources, for example high pressure mercury lamp with protecting filter. The filter stops hard UV radiation and visible light and transmits only radiation within the indicated range of wavelengths (e.g. 365 nm). "Black" light is used for different inspection and testing methods which are based on luminescence of some materials being illuminated by soft UV radiation.

UV radiation occupies spectral range of wavelengths from 100 – 400 nm.

1. long-wavelength UV A radiation (315 – 400 nm) – usually does not cause neither acute redness of skin nor burns

2. medium wavelegth UV B radiation (280 – 315 nm) – as a rule, causes acute and chronic skin damage

3. short-wavelength UV C radiation (280 – 100 nm) – absorbed by ozone layer and doesn't reach Earth's surface

Besides UVC radiation ozone absorbs also large part of UVB radiation, what means that UV radiation on Earth consists of UVA (90 – 99%) and small share of UVB (1 – 10%).

Due to the fact that UV radiation does not penetrate into the depth of a body the most sensitive organs are skin and eyes (conjunctivas and corneas, for long-wavelength UVA also lens). Penetration of UV radiation into the normal skin is up to the depth of 0.6 mm. Sufficient dose of UVA so develops tanning of skin which appears immediately after irradiation but is kept for a short period of time. Due to exposure of UVB rays cause redness of skin and in some cases swelling to bubbles. After these symptoms skin gets tanned and this effect has longer duration.

If UV radiation, which appears as a part of solar radiation, had penetrated directly into the Earth's atmosphere, its influence on life would have been fatal. Fortunately, when getting on Earth it disperses into ionosphere, ozonosphere and other layers of atmosphere (water vapor, aerosols, ...). Longer UV radiation go through the atmosphere, less it influences on Earth's surface.

As a consequence of ozone layer's damage is an increase of its flow capacity and it leads to health risks for sensitive people (mainly little children). Large doses of UV cause damages of sight and skin.

Requirements for health protection against influence of ultraviolet radiation are regulated in details by separate regulation and differ for each type of radiation. Principles can be summarized as follows:

• to avoid unwanted exposure to UV radiation
• UV radiation sources, if their operation is not indicated visually, have to equipped with optical signalization of operation
• covering or shading of radiation sources with recommended filters
• reducing of exposure periode
• if limitation of exposure by technical means is not possibe PPE is to be used, for eyes protection - glasses which are not UV radiation transmitting, for protection of exposed skin - protective gloves, in some cases - protective clothes
• preventive medical examinations - incoming, periodical and outcoming for employees related to operations with risks

Eyes protection

Protective UV glasses - transparent or toned with special frame, stop UV rays which pass along optical axis. According to the frame's type they can be adapted for mounting on dioptric glasses. Main requirement is to protect against penetration of UV rays from surrounding space beside glasses' frame to eyes. Most of protective UV glasses provide sufficient protection against UV radiation according to the existing standards.

Skin protection

UV radiation endangers skin, that is why one has to protect it with protective clothes or gloves. If this is not really possible protective cremes with UV filter are to be used. Particularly, protection against the most harmful radiation of UVB type is considered to be very important, modern protective means also protect against radiation of UVA type, when choosing creme you have to take this into consideration. By protection factor number one can count percentage of UV radiation which is filtered by the article (i.e. how many of coming UV rays will not be transmitted on body surface). For instance:

Protective factor of article:	Filtration efficiency of UV radiation:
No. 2	50% UV will not be transmitted
No. 5	80% UV will not be transmitted
No. 10	90% UV will not be transmitted
No. 20	95% UV will not be transmitted
No. 32	98% UV will not be transmitted

Cremes with protective filter are needed to be applied onto the skin 15 minutes before start of work. Protective layer on skin is to be renewed minimum every 2 hours.

• Law No. 258/2000 Sb. About public healthcare and changes ofsome related laws, about non-ionizing radiation in § 35 Non-ionizing radiation.
• Government resolution No. 480/2000 Sb. About healt protection against non-ionizing radiation.
• Notification No. 89/2001 Sb. Ministry of Healthcare, which sets up conditions for classification of works and operations, limits for biological exposures and need to inform about work with asbestos and biological agents (factor 5 non-ionizing radiation and electromagnetic field).