Introduction to UVR at work

Optical radiation is found ubiquitously. It is not solely emitted by natural sources, e. g. the sun, but also by many artificial sources or applications. Ultraviolet radiation (UVR) is vectored electromagnetic radiation in the wavelength regime 100 nm to 400 nm. This spectrum is subdivided into three ranges:

• Near ultraviolet - UVA: 315 - 400 nm
• Middle ultraviolet - UVB: 280 - 315 nm
• Far ultraviolet - UVC: 100 - 280 nm

Although being known as essential for human health, e. g. production of vitamin D, (over)exposure to UVR can be hazardous. Workers can be exposed to UVR at different levels and at different places. This article deals with the explanation of what is UVR, the main definitions associated with UVR, occupational sources of UVR both natural and artificial, and a brief overview of health effects.

Occupational exposure to ultraviolet radiation (UVR) was identified as one of the most important work-related emerging physical risks by the European Agency for Safety and Health at Work (EU-OSHA’s) expert forecast on emerging physical risks related to occupational safety and health (OSH). The experts identified both artificial sources of UV (i.e. all types of welding activities as well as the increasing use of UV-based technologies applied in different technological processes such as drying, curing, photo-polymerization, photo-activation, disinfection, irradiation and phototherapy) and natural sources of UVR (solar radiation) in the forecast. Concern for occupational outdoor UVR exposure was raised as a result of climate change and increased UV index. Occupational exposure adds up to the increasing UVR exposure in people’s private life, not only as a result of their hobbies but, again, also as a result of increased UV index. This global increase of UVR exposure augments workers’ sensitivity to UVR, hence strengthening the need for appropriate workplace prevention.

Exposure to UVR can result in short term and long term adverse health effects (e.g. photoconjunctivitis, photokeratitis, reddening of the skin, blistering, swelling and peeling of the skin, keratoses, different kind of skin cancer, premature skin ageing and injuries to the eye such as damages to the cornea, formation of cataracts and pterygia).

Workers can be exposed by UVR from natural sources (mainly the sun) and artificial sources (e. g. a welding arc). The most common radiometric quantities used to describe exposure dose to UV are:

• Irradiance – radiant power incident per unit area upon a surface (radiant power density), in W/m²
• Radiant exposure – the integral over time of the irradiance (dose), in J/m²
• Minimum Erythema Dose - MED - describes the erythemal potential of UVR, i.e. the effective UV dose that causes a perceptible reddening of previously unexposed human skin. Because human individuals are not equally sensitive to UVR due to different self-protection abilities of their skin (pigmentation), the MED value varies among the European population between 200 and 500 J/m^2 [1].
• Standard Erythema Dose - SED - is a standardized measure of the erythemal UVR that does not depend on the skin type and is equivalent to an effective erythemal exposure of 100 J/m^2 [2].

The radiant exposure per day strongly depends on the working procedure/time schedule and thus potential hazard is subjected to radiation both from natural and artificial sources.

Solar UVR

Outdoor workers are exposed to natural UVR from the sun. The sun is the principal natural source of UVR and it emits a broad spectrum. Solar UV is significantly absorbed by the atmosphere. However, the amount of remaining radiation reaching the surface of the Earth is still high enough to play an important role on human health. Whereas UVC rays are quantitatively absorbed by the stratospheric ozone layer and do not reach the Earth’s surface, most radiation in the UVA range and about 10% of the UVB rays reach the Earth’s surface ^[3]. As a result, the spectrum range of solar UVR at a ground level consists in almost 99% of UVA ^[4]. Both UVA and UVB are of major importance to human health.

Solar radiation at ground level consists of three major components:

• direct sun radiation;
• sun radiation scattered from the open sky (atmosphere);
• sun radiation reflected from the environment.

The ratio between direct and scattered radiation varies depending on the wavelengths and the height of the sun above the horizon. The reflected radiation depends on ground surfaces and a highly reflective environment can increase UVR levels. This means that a worker shaded from the direct sun can still receive substantial UVR exposure from the open sky and from reflective ground surfaces such as white paint, light colored concrete and metallic surfaces.

The level of solar UVR depends on:

• sun elevation (the higher the sun, the more intense the UVR) and as a consequence also depends on the time of the year and of the day;
• cloud cover (heavy clouds can reduce UVR);
• latitude (the closer to equatorial regions, the higher UVR);
• altitude (the UVR is at higher at higher altitudes);
• ozone layer (the thinner ozone layer, the higher UVR);
• ground reflection.

It can be measured by the UV index, which provides a numerical indication of the potential solar UVR level in a certain location at a certain time.

What is Solar UV Index?

The UV Index (UVI) describes the level of solar UV radiation at the Earth’s surface. It expresses the erythemal power of the sun. The values of the index range from 0 upwards – the higher the index value, the greater the potential for damage to the skin and eyes, and the less time it takes for injury to occur.

Source: overview by the author

On its website, the WHO provides an indicative table that illustrates the changes in UV radiation levels with season and latitude ^[5]. Maximal UV Index values are given for a range of cities in different countries, calculated for the 21st of each month. The highest values of maximum UVI can be found in Nairobi and Singapore – which are very close to the equator – where UVI varies between 10 and 13 depending on the time of the year. The UVI is lower further from the equator. In Europe, UVI is higher in the summer than in winter. WHO provides links to the webpages of 13 EU countries (Czech Republic, Finland, France, Germany, Greece, Italy, Luxembourg, Netherlands, Norway, Poland, Spain, Switzerland and Sweden) that provide UVI forecasts.

It has to be taken into account that the UVI is determined solely for a horizontal plane. The personal exposure for people moving and/or working in the sun may not be calculated appropriately, as the angle between the surface of the skin and the horizontal plane always varies. Such variations range from 90° irradiation (maximum) to pointing away from the source (no exposure).

A direct effect of climate change, the depletion of stratospheric ozone, will result in increased ultraviolet (UV) radiation exposure ^[6]. Indeed, when the ozone layer becomes thinner, the protective filter provided by the atmosphere is progressively reduced. Consequently, human beings and the environment are exposed to higher UV radiation levels, and especially higher UVB levels that have the greatest impact on human health, animals, marine organisms and plant life. The consequences of this increased UV exposure are considered as very serious. This had already been identified as a priority by the United Nations in 1992.

Prominent fields of activities with usually high exposure against solar UVR are workers at construction sites and roads, workers in agriculture and forestry, seamen, window cleaners, waste collectors, bath attendants, postal service, delivery service, and workers in horticulture.

Artificial sources

There are many types of artificial UVR sources. Artificial sources of UVR include various lamps used in medicine, industry, commerce, research and at home, for example: tanning booths, black lights, curing lamps, germicidal lamps, mercury vapor lamps, halogen lights, high-intensity discharge lamps, fluorescent and incandescent sources, and some types of lasers. They emit a spectrum of radiation which differs depending on the type of lamp or source. The risk to health from artificial sources can be much higher than those from natural UV, not only because levels of UV may be higher but also because they may include specific wavelengths particularly harmful and normally filtered by the Earth’s atmosphere (from UVB and UVC regions).

Artificial sources (see Table 2) may present different risks depending on the wavelength range of the UVR they emit, meaning that the spectral emission data of the UVR artificial source is needed, such as the spectral irradiance (should be provided by the manufacturer or obtained through measurements) in order to assess the risks.

Source: ^[7]

UVR can also be an unintended by-product of some working processes like welding or oxygen cutting. There are two main welding processes: gas welding and electric arc welding. The level of emission depends on the arc current, shielding gas and metals being welded. Welding arcs can exceed the UVR exposure limit values (ELVs) set in Directive 2006/25/EC in seconds within a few meters of the arc - Directive 2006/25/EC of the European Parliament and of the Council of 5 April 2006 on the minimum health and safety requirements regarding the exposure of workers to risks arising from physical agents (artificial optical radiation). Workers, bystanders and passers-by can be overexposed to UVR from the arcs if engineering controls are not adequate.

UVR may have positive as well negative effects on human health, depending on the conditions of exposure and wavelength of radiation. While excessive UVR exposure can cause adverse photochemical reactions, DNA lesions, damages of the skin and the eyes and can affect the immune system, adequate amounts of UV are beneficial for people and essential in the production of vitamin D. Further benefits of UV are found in medicine where UV lamps are used for medical treatments for example of many dermatological diseases like psoriasis and eczema, as well as jaundice in new born babies. Such applications are performed under medical supervision and the benefits of treatment versus the risks of UVR exposure are a matter of clinical judgment.

Effects of UVR on the skin

Skin is the largest organ of the body, and is at the greatest risk of contact with UVR. Effects on the skin (Table 3) will depend mostly on the wavelengths and photochemical sensitivity of the tissue.

The shortwave UV radiation (UVC) poses the maximum risk for acute harm. The sun emits UVC but it is absorbed in the ozone layer of the atmosphere before reaching the earth. Therefore, UVC from the sun does not affect people. Some man-made UV sources also emit UVC like germicidal lamps which are widely used in medicine and different industry branches for disinfection.

The long-wave UVR (UVA) plays a helpful and essential role in the formation of Vitamin D by the skin but also plays a harmful role in that it causes tanning and cataracts. UVA is also thought to contribute to aging of the skin (photoaging) and skin cancer ^[8]. UVB causes skin burns, erythema (“sunburn”), darkening of the skin and induces skin cancer by causing mutation in the deoxyribonucleic acid (DNA) and suppressing certain activities of the immune system ^[9]. While UVA penetrates the human skin more deeply than UVB, action spectra for biological responses indicate that it is radiation in the UVB range that is absorbed by the DNA ^[10]. Indeed, the peak absorption of DNA occurs at around 260 nm with a sharp drop in absorption through the UVB range ^[11]. No absorption is detected for wavelengths longer than 325 nm. Damage to DNA caused by direct absorption of UVB appears to be a key factor in the initiation of the carcinogenic process in skin. But damage to DNA may also result from oxidation by reactive oxygen species which are produced as a consequence of UVA absorption. For example, aromatic amino acids, like tryptophan, absorb in the UVB and extend into the UVA range. Once in the excited state, they may transfer the energy to oxygen of which the different excited states will react with all biological structures, inducing damages also of DNA. Typically the majority of DNA lesions in human cells are removed and repaired at a relatively high rate but cell death and cell mutations also occur.

The total UV dosis (natural and artificial) received for an individual determines the global carcinogenic risk in particular for squamous cell carcinoma ^[12].

Source: overview by the author

In the group of acute adverse outcomes of the skin associated with UVR are: erythema, photodermatosis (any dermatosis produced by UVR) and sunburn ^[14]. In the group of chronic outcomes are: cutaneous malignant melanoma, basal cell and squamous cell carcinoma, solar keratosis, and cancer of the lip.

One of the important factors that contribute to UVR-related skin disorders is the skin type related to skin pigmentation (Table 4). Skin pigmentation alters the exposure–disease relationship for all UVR-induced skin diseases ^[11]. Highly pigmented skin (dark skin) provides an important sun protection while fair-skinned types have low levels of protection, which means that fair-skinned people suffer more from sunburn and have a higher risk of skin cancer than dark-skinned people. However, even though the incidence of skin cancer is lower in dark-skinned people, the cancers are often detected at a later, more dangerous stage ^[13]. The risk of eye damage, premature ageing of the skin and immunosuppression is independent of skin type.

The “Fitzpatrick scale” is the most common classification of skin types for UVR sensitivity.

Source: ^{[7] [10] [12]}

Effects of UVR on the eyes

The eyes are particularly sensitive to UVR (see Table 5). Since the transparent media of the eye does not have any melanin pigment (as in the skin), there is no correlation between the UVR sensitivity of the eye and skin type ^[11]. Hazardous effects can occur to various parts of the eye depending on the wavelength. The eyes are most sensitive to UVR from 210 nm to 320 nm (part of UVC and UVB). Maximum absorption by the cornea occurs around 280 nm ^[9]. Radiation with wavelengths shorter than 290 nm (UVC and part of UVB) is almost entirely absorbed by the cornea. Radiation in the range 300-370 nm (part of UVB and part of UVA) is almost entirely attenuated in the lens. Absorption of UVA in the lens may be a factor in producing cataract. The cornea does not adapt to repeated exposures by thickening like the skin and is therefore equally vulnerable day after day to UVR ^[13]. The effects of UVR on the eyelids are equivalent to those described for the skin.

Source: overview by the author

Acute UV-related eye diseases are: solar rethinopathy, photokeratitis and -conjunctivitis ^[10]. In the group of chronic outcomes are: pterygium, squamous cell carcinoma of the cornea, squamous cell carcinoma of the conjunctiva, cataract, ocular melanoma and macular degeneration. Further data are required to clarify the relationship between excessive UVR exposure and acute macular degeneration, nuclear and posterior subcapsular cataract and ocular melanoma.

Worldwide, about 5% of cataracts may be due to UV radiation ^[13].

Effects of UVR on the immune system

Ultraviolet radiation can affect the immune system. There is increasing evidence for a systematic immunosuppressive effect of both acute and low-dose UVR . Exposure to ambient UV may enhance the risk of infection with viral, bacterial, parasitic or fungal infections. The following acute negative immune effects associated with UVR have been recognised: suppression of cell-mediated immunity, increased susceptibility to infection, impairment of prophylactic immunization and activation of the latent virus infection herpes labialis ^[14]. High UVR levels may also reduce the effectiveness of vaccinations ^[15]. The activation of the latent papilloma virus infection is recognized as a chronic negative immune effect associated with UVR ^[14]. Exposure to UVR (in particular UVA and UVB) could also cause inflammatory reactions - as a consequence of weakening the immune system - that could contribute to the development of cutaneous tumors .

It has been suggested that UVR may promote cancer in two distinct ways: by directly inducing DNA damages and by weakening the immune system ^[15].

UVR and photosensitizing agents

Some chemicals increase the sensitivity of human skin to UVR and produce phototoxic reactions, i.e. cutaneous reactions with rash, erythema, itching, intense sunburn, blistering or edema ^[11] [14]. Such substances are called photosensitizers. They absorb optical radiation (generally UVR) and transfer the energy to reactive biomolecules that can produce a toxic reaction at doses well below those that induce for example sunburn or keratitis. These photosensitizing effects can occur in case people are exposed to UVR in the frame of their work.

Photosensitizers include certain drugs, plant materials, perfumes and cosmetic constituents, dyestuffs, polycyclic hydrocarbons in wood preservatives, coal tar pitch and petroleum products containing polycyclic aromatic hydrocarbons (PAHs), sunscreen, and certain printing chemicals used in photosensitive printing processes. Examples of photosensitizing drugs are thiazide diuretics, drugs used in the treatment of high blood pressure, certain antibiotics (tetracyclines, sulfonamides), oral contraceptives, and thiazine tranquilizers (e.g. chlorpromazine, phenothiazine anti-depressant drug) ^[9] [16] . These drugs must be taken internally before the skin becomes sensitive to sunlight. However, simple skin contact with various plants and fruits, such as figs, parsnips, citrus plants, carrot, dill, mouldy celery and some types of weeds, followed by exposure to sunlight can cause a phototoxic reaction such as sunburn or dermatitis. Citrus fruit handlers and vegetable harvesters, gardeners, florists and bar tenders are at risk. Some individuals who have been exposed to photosensitizers and have experienced a phototoxic reaction may present permanent skin reactions when exposed only to the sun.

Some photosensitizers are also photo-allergens ^[11]. While phototoxic reactions are usually localised to the body surface at the site of exposure, the effect of a photo-allergic reaction extends beyond the site of exposure. A further difference is that a phototoxic reaction is in most cases proportional to the concentration of the photosensitizer and to the magnitude of UV exposure, whereas a photo-allergic reaction depends on the amplitude of the immunologic reaction.

According to Directive 2006/25/EC ^[17] , “the employer should give particular attention, when carrying out the risk assessment, to […] any possible effects on workers’ health and safety resulting from workplace interactions between optical radiation and photosensitizing chemical substances”.

In addition, some chemicals called "promoters" can increase the cancer-causing ability of UVR. And vice-versa, UVR itself can act as a promoter and increase the cancer-causing ability of some chemicals, in particular from coal tar and pitch ^[16].

Regarding optical radiation from artificial sources, the directive 2006/25/EC on the minimum health and safety requirements regarding the exposure of workers to risks arising from physical agents (artificial optical radiation) is in effect ^[17]. Following the directive, the employer is obligated to

• Determine the exposure and to assess the risks
• Make provisions aimed at avoiding or reducing risks
• Inform and train workers
• Consult and participate workers

Despite the obligation to fulfil a risk assessment according to directive 2006/25/EC, it is always wise to get an estimate on a worker’s UV exposure. Even when the ELVs are kept, a certain risk is present to suffer from long term ailments. Detailed information on biological effects of UVR can be found here.

The determination of the level of UV-exposure should always be done by a measurement of the UV-exposure of the worker likely to be exposed followed by a comparison with the ELV. If there are similar workplaces (e. g. many arc welding workplaces or many benches with gas burners), a risk assessment (and thus a measurement) can be performed exemplarily for one workplace. Nevertheless, special personal circumstances have to be taken into account, mainly if the worker belongs to a special group of light-sensitized persons (e. g. after medical treatment).

Measurement and assessment of personal exposure to UVR is also subject of certain European standards, e. g. EN 14255-1:2005 ^[18].

General procedure in measurement

When a decision for measurement has been made, a work task analysis has to be done. This analysis shall include determining (taken from ^[18]):

• The number, position(s) and types of radiation sources
• Radiation which is reflected or scattered on walls, equipment, materials, etc.
• The spectrum of the radiation to which persons are exposed
• The constancy or the variation of the spectrum and/or the irradiance/radiance with time
• The distance between the exposed person and the radiation source(s)
• Changes in the location of the exposed person during the work shift
• The time(s) spent by persons at different locations in relation to the radiation source and the duration(s) of exposure at these locations
• Which potential health effects are to be taken into account
• ELVs
• Enhanced photosensitivity
• Presence of protective measures

In the next step, the measurement and/or calculation can be conducted (details see next section), followed by an assessment of the UV-exposure, which relies on a comparison with the ELV. If the ELV are exceeded, or not surely kept, protective measures in the series technical – organizational – personal should be chosen. Finally, a report should be written, also including a new period for control measurements.

Measurement of exposure

When planning a measurement, the respective procedure has to be determined under consideration of the aim of the measurement. Due to their special characteristics, a differentiation between spectral resolved measurements and integrating measurements is useful.

Spectral resolved measurement The spectral irradiance in dependence of the wavelength can be measured with a Spectroradiometer. Incoming radiation is spectral resolved with a prism or an optical lattice into its constituent parts. For technical purposes, bandwidths of 1 nm, 2 nm, or 5 nm are chosen. The absolute detected irradiances may now be further calculated, either being used unweighted, or spectral weighted in matters of biological effects. Main components of a Spectroradiometer are:

• Input optics
• Spectral apparatus
• Receiver
• Detector and processing unit

Within the class of the Spectroradiometers, two categories are to be distinguished:

• Spectroradiometer with scanning mono-/multichromator: Each wavelength is scanned according to the scan width setting. The result is a spectrum with information in the spectral distribution of the radiation. The more chromators are sequentially coupled, the more precise is the measurement. Nevertheless, for risk assessments at working places, a monochromator is fully sufficient.
• Spectroradiometer with array detector: The optical lattice is fixed and the beam is dispersed on a field of detectors, e. g. photodiodes. Thereby, each detector is addressed to a certain wavelength. Thus, it requires only milliseconds to acquire a full spectrum. This method is suitable to examine time-varying radiation.

Integrating measurements (“Radiometer measurements”) A radiometer consists of a detector head with input optic, optical filter or a combination of optical filters and a detector. By choosing the appropriate filter or filter combination and a suitable detector with selective spectral sensitivity, it is possible to adapt a certain wavelength regime or a specified spectral weighting. Thereby it is feasible to conduct direct measurements of biologically weighted quantities. For an appropriate measurement, the adaption of the filters and the detector to the spectral weighting function or the wavelength regime is crucial.

Personal dosemeter With this instrument, the radiation can be measured on exposed parts of the body. When the spectral irradiance varies strongly throughout the day, this is most advantageous. The spectral sensitivity of the dosemeters can either be constant or can be in accordance with a spectral weighting function. One distinguishes between electronically operated, photochemical, and biological dosemeters.

Measurement requirements A chosen measurement strategy always has to fulfill special requirements to gain reliable and reproducible results. Important information on devices is usually provided by the manufacturer, while the operator has to ensure conformity with the given task. It is his duty to prepare a suitable modus operandi.

In detail, it has to be considered ^[18]:

• Uncertainty in measurement
• Measurement sensitivity range
• Spectral sensitivity of the detector system
• Active detector area, aperture and field of view
• Cosine angular response
• Averaging time
• Environmental conditions
• Calibration
• Wavelength range
• Scanning steps, bandwidth resolution, stray light

If the risk assessment has been conducted, and the compliance with the limit values is not ensured, protective measures have to be chosen. Additionally, persons belonging to a special risk group (e. g. photosensitized persons) should be supplied with personal protective equipment. The collectivity of the protective measures has to ensure that the ELVs are kept.

Preferential, emission of optical radiation should be avoided or diminished at the source. Concerning UVR, the exposition should be as low as reasonably achievable (“ALARA”-principle); even if the ELVs are kept.

Ranking of protective measures

To reduce exposure, a sequence of protective measures can be introduced: 1. Avoiding or minimization by choosing of alternative working procedure In special cases, other procedures without UVR can be applied, e. g. adhesive bonding instead of welding, application of cameras instead of direct observation of a process 2. Technical measures Primarily at the source: capping, shielding, blinding, optical filters 3. Organizational measures Here, measures regarding room and time-management are subsumed, e. g. increasing the distance between source and worker, or optimised time scheduling for the workplace 4. Personal protective equipment (skin and eyes) If protective measures applied so far are not sufficient, personal protective measures have to be taken into account. Usually, personal protective equipment (PPE) in compliance with the PPE directive 89/686/EEC ^[19] has to be provided. Certain harmonized standards give support in choosing the correct protection, e. g. EN 166 ^[20], EN 169 ^[21], EN 170 ^[22], or EN 175 ^[23] for personal eye protection. For welders, EN ISO 11611 ^[24] supplies protection information. Nevertheless, for protection of the skin, only poor information is available on personal protective equipment for protection against optical radiation in special.

Protection of the skin

The protection of the skin must ensure the reduction of the exposition below the ELVs. The following measures can be helpful:

• Shields, visor and cap to ensure protection of the skin in the face
• Gloves
• Tight shoes and gaiters
• Leather cap for the neck
• Long-sleeved clothing
• Security windows with filter effect

It should be noticed, that it is not necessarily obligatory to use certified personal protective equipment (PPE) for protection of the skin. In some cases, especially when the UVR exposure is moderate, “normal” clothing is sufficient.

Protection of the eyes

The protection of the eyes against UVR is necessary to avoid short-term, as well as long-term ailments. Thus, glasses (or face shields) should also be worn when the ELVs are kept. UV filter glasses should be classified in accordance with the above-mentioned harmonized European standards. For this purpose, a detailed analysis of the work procedure and exposure condition including the spectral parameters of the source should be known. However, a certain comfort should be kept to ensure acceptance among the workers:

• Wearing comfort (weight, air ventilation, pressing force
• Geometry of the face
• Skin incompatibility
• Optical interference (deformation of the field-of-view, colour shifting, stray light)

Final remark

The protection of the workers against UVR from artificial sources is much more straight forward than protection against radiation from the sun. Not only the position of the radiation source, but also the concomitant heat in summer outdoor work resembles a problem in choosing protective measures. For example, in road construction it is hard to select technical and organizational protective measures. Personal measures are often denied due to the heat. Nevertheless, the employer has to ensure protection of the worker.

For instance, a measurement of UVR shall be described against the background of glass manufacturing with gas burners.

Workplace and exposure

Usually, a single worker is occupied at a workbench equipped with a gas burner. While manufacturing glass, the worker can either sit or stand. The period of occupation strongly depends on the work to be done. While in apparatus construction the occupation is very individual and reaches from less than an hour to eight hours per working day, it is typically several to eight hours per day in batch production. Thus, the net exposure time may also reach several hours. An individual risk assessment has to be carried out. During his presence in the vicinity of the gas burner, the worker can be exposed at many body parts:

• Hands (typical distance to gas flame is 10 cm to 15 cm)
• Arms
• Face (typical distance to gas flame is 60 cm)
• Eyes
• Neck (exposed by the flame from a worker at a place behind)

Exposure measurement

The hazardous potential of UVR emitted by gas flames has been come the knowledge during measurements of apparent infrared radiation (IR) emitting gas burners some years ago. The German Institute for Occupational Safety and Health of the German Social Accident Insurance (IFA, Sankt Augustin, Germany) thus started a project to systematically examine a series of gas burners likely used in glass manufacturing. The data revealed interesting results. At most of the exposure situations, ELVS in the UVR can be exceeded in times considerably lower than an hour in the face and at the eyes, even minutes at the skin of the hands. The data will be published and discussed in details somewhere else soon.

Protective measures

ELVs can be exceeded very fast and thus very high when working in the proximity of an intensive gas flame. Thus, protective measures have to be taken. As described above, especially hands and face/eyes have to be protected. During interviews, workers claim that they lose their ability to perform precise work when using personal protective equipment (PPE) for hands and face:

• Wearing gloves reduces information at the finger tips
• Wearing a face shield hampers the use of a pipe to blow out glass pieces during the manufacturing process

Nevertheless, protective measures can be taken (examples):

1. Technical: mounting a filter plate on the gas burner such, that the face is shielded against the gas flame.
2. Organizational: optimizing work flows: preparative work should be done – if possible – done without exposure by the gas flame, either by turning on the burner just before work starts, or by working at another workbench.
3. Personal: eye protectors should be used. They shall be chosen appropriate to the standards. Further on, gloves without fingertips and long-sleeved clothing should be worn.