Occupational exposure to natural UVR and prevention

Outdoor workers are exposed to natural UVR emitted by the sun. Since optical radiation is vectored, the irradiance of a worker is individual, even at identical activities at the same construction site. Depending on various parameters, exposure levels may lead to acute (e. g. erythema) or long time (e. g. skin cancer) hazards. For prevention, protective measures (either technical, organizational or personal) are required to minimize exposure to a level as low as reasonably achievable. In cases of occupational disease, retrospective determination of disease has to be carried out as precise as possible. This article deals with professions at risks supported with EU data and examples of national data, legislation, policies and strategies related to natural UV, risk assessment and prevention..

Ultraviolet radiation (UVR) is vectored electromagnetic radiation in the wavelength regime 100 nm to 400 nm. UVR is invisible for the human eye. It belongs to “Optical Radiation", which is a “Physical Agent" in terms of OSH.

Solar radiation on earth also contains UVR, mainly UV-A (315 nm to 400 nm), little UV-B (280 nm to 315 nm), and no UV-C (100 nm to 280 nm) due to high absorbance in the ozone layer of the atmosphere. Some gases, especially Chlorofluorocarbon (CFC), promote degradation of ozone and thus lead to the so-called ozone hole. This results in higher exposure to UV-B on earth, giving rise to higher skin cancer risk ^[1][2].

Although being known as essential for human health, e. g. production of vitamin D, (over)exposure to UVR can be hazardous.

Hazardous biological effects of UVR

UVR penetrates human tissue only skin deep, human organs are out of reach. Thus, biological effects are limited to the eye and the skin and have to be distinguished this way. It has been subject to science for long years to understand effects of UVR on a molecular level, resulting in biological action spectra to display the wavelength dependence of biological hazards (e. g. originating from ^[3], now adopted by CIE).

Effects on the eyes

The eye is designed to receive electromagnetic waves in a certain wavelength regime and to convert this information first into chemical signals and then into electric potentials. This biochemical process highly depends on the selected wavelength and the intensity of the light beam. Given its structure, only a small band of optical radiation (namely the “visible light") propagates through the whole eye to be detected in the retina.

Radiation at shorter wavelength (UVR) is absorbed in the front parts: UV-C is absorbed in the superficial layers of the cornea, while UV-B is absorbed by the cornea and the lens. UV-A passes almost quantitatively through the cornea and is absorbed in the lens.

Acute overexposure of the eye to UVR includes mainly inflammation of the cornea and the conjunctiva, called photokeratitis and photoconjunctivitis, respectively. Severity of the symptoms ranges from mild irritation to severe pain, and the recovery may last a few days. Chronic exposure to UV-A and UV-B can cause cataracts of the eye’s lens. Treatment of this disease is possible in most of the cases by exchanging the natural lens with an artificial one. Nowadays, artificial lenses feature a so-called “UV-stop" to prevent UV-A to promote through the eye and damaging the retina.

In case UV exposure, active protection has to be applied to protect workers from hazardous effects. UVR is invisible and thus no involuntary aversion responses are expected, as it is usually the case in dazzling.

Effects on the skin

The penetration of the skin by UVR is wavelength-dependent. Roughly spoken, the longer the wavelength, the deeper UVR penetrates the skin. UV-C is absorbed in the very upper layer of the skin, the Stratum Corneum, while UV-B promotes through this layer and reaches the epidermis. UV-A penetrates the skin down to the dermis. None of the UVR is supposed to reach the subcutaneous layer.

Excessive short-term exposure to UVR leads to sunburns (erythema), an inflammation of the skin. Delayed tanning as an increase in skin pigmentation may be a subsequent result of overexposure to UV-B. Exposure to UV-A may also lead to immediate pigment darkening.

Following IARC (1992), UVR is carcinogenic, which means it may induce skin cancer ^[4]. For melanoma skin cancer, the incidence of being UVR induced is rather small. Squamous cell carcinomas (SCC), actinic keratosis (AK, pre-stage cancer) and basal cell carcinoma (BCC) are called non-melanoma skin cancers (NMSCs) and most possibly related to UVR exposure. The correlation for SCC and AK is mostly clear ^[5][6], while there is a smaller incidence for BCC ^[7]. Evidentially there is a correlation between NMSC occurrence and skin type classification by Fitzpatrick ^[8]: skin type I suffers the highest risk to develop NMSC, skin type VI the smallest. Chronic exposure to UVR may also result in photoageing of the skin, which means an accelerated loss of elasticity. Additionally, UVR radiation potentially influences immune functionality, leading to a decrease or increase in immune responses.

More detailed information can be found here.

Factors influencing UV irradiance

The irradiance of solar UV on earth depends on various direct and indirect parameters. Among direct parameters, we find

• Daytime: from sunrise until sunset, the solar spectral irradiance and the intensity change due to the varying angle between the light beam and the horizon. This is directly connected to air mass and thus absorbance.
• Season: due to the obliquity of the ecliptic, we experience seasons. In wintertime, angle between the light beam and the horizon is smaller as in summertime, resulting in lower irradiance.
• Altitude: The higher above ground, the less air mass is above us. Therefore, absorption is lower and thus irradiance higher.
• Solar activity: The sun does not emit constantly. Within a cycle of years, the emission of the sun resembles a sinus.

More local, more variable parameters (mainly on a timescale) are

• Weather: Cloudiness influences irradiance due to refraction and diffusion of the beam. These factors are correlated mainly to the water concentration in the atmosphere but not reliable predictable only but judging the sky by eye.
• Ozone layer: Local variations in the ozone layer of the atmosphere directly influence absorption of UV. The less ozone is present, the more UVR is transmitted.

The irradiance does not necessarily reflect the exposure. As people move, their position and orientation changes with respect to the sun, and therefore also the exposure changes. To gain insights into exposure patterns of workers, long-term measurements using personal dosimeters are necessary.

Comparison of UVR from natural and artificial sources

UVR emerges from natural as well as artificial sources. Technically, there is no evident difference on photons from natural and artificial sources. The continuous power spectrum of the sun can be described with a Black body radiator following Planck’s law with an effective temperature of 5900 K. Technical applications on earth rarely need such high temperatures. To emit a substantial amount of UVR, a Black body radiator should have an effective temperature above 2000 K. Artificial sources working at those temperatures are steel smelters and mainly molten fused quartz.

Anyway, most sources of artificial optical radiation emit line spectra without any continuous content. For example, mercury-vapor lamps, welding arcs, or gas burner flames emit prominent line spectra especially in the UV wavelength regime.

In summary, any UVR is equal. The only difference is the composition of the spectra.

Since time immemorial, human beings are working outside in the sun. The human body has developed to its present appearance to combine several advantages. We walk upright (erect, since homo erectus) to descry enemies and preys, but also to minimize the surface of the skin exposed to the sun to prevent body overheating. This occurrence only leaves us with few so-called sun terraces like nose, bald head, ear, and instep. Doubtless, nature did not design prevention of skin cancer as humans did not get old enough to suffer from the disease.

Nevertheless, working activity often requires non-upright body positions for many hours (kneeling, cowering, and bending down). Nowadays, especially in the European climatic zone, body overheating is of secondary importance. As man gets older, solar influence dominates the risk factors to promote skin diseases.

Occupations at risk of exposure to natural UVR

Outdoor workers are constantly exposed to natural UVR and are therefore at higher risk of skin cancers. The intensity and frequency of such exposure varies greatly between sectors and even within one same occupation – this would depend on local circumstances (UV Index) and an individual’s activities and skin pigmentation. Posture is also an important factor. For example, many tasks in traditional agricultural jobs require the worker to bend over. The back and back of the neck are therefore more exposed than the face. The exposures by fishermen will have similar postural aspects, but the reflection from the water and the time of day may result in higher exposure doses to the eye and skin. Maritime jobs belong to the occupations with the highest UVR exposure, both in terms of intensity and frequency of exposure.

In Germany, in a project funded by the Federal Institute for Occupational Safety and Health (BAuA) ^[9], the solar UVR exposure of different occupations representing workers working outdoors permanently (construction workers, agricultural workers and waste collectors) or occasionally (physical education (PE) teachers, kindergarten teachers and window cleaners) was measured along the year on week days, weekends and holidays for 19 specific body parts, and were compared to indoor workers. Both for permanent and occasional outdoor workers, the occupational UVR exposure was the major contributor to the total UVR annual exposure (in particular during the 6-month period around the summer).

It is important to keep in mind that exposure of workers against UVR from the sun is affected by many factors:

• Position against source (sun)
• Shadow provided by trees, buildings, vehicles, temporarily installed machines (e. g. cement silo at construction sites)
• Clothing as result of outside temperature

To tell numbers, an estimated 14.5 million workers in the EU are exposed at least 75% of their working time to solar radiation; 90% of whom are men ^[10].

Workers at construction sites and roads

On construction sites, many different activities have to be carried out directly in the sun. While indoor-construction workers (electrician, heating installer etc.) are only minor exposed, e. g. brick layer, plasterer, concrete workers, steel builders, and road construction workers are exposed at a very high level. Their work has often to be carried out in the bright summer sun, and no shadow is or can be provided. Unfortunately, the behaviour of the workers themselves aggravates the exposure situation. Wearing of personal protective equipment, or at least long-sleeved shirts, long-legged trousers and headdress is refused. To take it to extremes, the workers are bare-chested during hot summer days.

Workers in agriculture

Farmers often work seven days a week, especially when cattle is involved. During summertime, most work has to be done outside on the field. Questioning of farmers revealed interesting lifetime work pattern: Mostly they work from childhood days on, many hours per day and do not go for holiday. Especially in agriculture, seasonal workers are employed. Seeding or harvesting has to be done in very short time period with a high number of workers.

In contrast to former times, agricultural work has become more and more mechanised. Tractors, harvesters, and related machines have closed driver’s cabins, where exposure to natural UVR is reduced by the window glass. However, the driver has to get out of the vehicle more often than one would expect, and thus exposure is present. Additionally, a farmer working outside without machinery often wears broad-brimmed hats, while a driver in the cabin does not (due to heat inside). He gets out bareheaded.

Seamen

Mainly during the second half of the last century, European seamen were hired on European-flagged ships to travel the world. Beside short-routes in Europe, trips in the vicinity and across the equator were done. Under good weather conditions, work on-deck hat been carried out with short-legged and short-sleeved clothing as mandatory uniform. As we know today, the exposure may be a factor of 3.5 higher in the vicinity of the equator, and additionally, wavy water reflects UVR to an amount of 25 to 30%, raising exposure of the seamen ^[4]. One may reflect also that working times per day exceed eight hours regularly due to lack in personnel and free-time activities.

Nowadays, deck workers of crews often consist of people from Asia. They are, in contrast to their former colleagues, completely clothed and only little exposed against UVR from the sun.

Further examples

The listing for outdoor work tasks can be prolonged to the extent. Some of them are:

• Window cleaning
• Waste collection
• Bath attendance and beach guard
• Postal service
• Delivery service
• Forestry
• Horticulture

Even though there is no EU Directive specifically addressing natural UV sources, the “framework" Directive 89/391/EEC lays down general principles concerning the prevention of occupational risks, and this implicitly include risks to workers arising from natural UVR sources. According to the “framework" Directive, employers have the responsibility to avoid the risks to workers from natural UVR sources, need to assess the risks from natural UVR sources that cannot be avoided, and must implement appropriate protection measures following the hierarchy of control measures established in the Directive.

The EU Member States must have a national legislation in place enforcing Directive 89/391/EEC and protecting workers from all occupational risks, which includes those originating from natural UVR sources.

Examples of regulations related to occupational exposure to natural UVR in five EU Member States

• Belgium

Federal Public Service Employment, Labour and Social Dialogue (FPS), “Règlement général pour la protection du travail"/ “Algemeen reglement voor de arbeidsbescherming" [“General Regulation on the Protection at Work"]:

Title II, Chapter II, Section I, Article 68 “Solar radiation": “Workers should be protected from solar radiation by all adequate systems" Available at: http://www.emploi.belgique.be/moduleDefault.aspx?id=1964 (in french) and http://www.werk.belgie.be/moduleDefault.aspx?id=1964 (in dutch)

• Germany

Deutsche Gesetzliche Unfallversicherung (DGUV), “Grundsätze der Prävention", Unfallverhütungsvorschrift BGV A1 [“Prevention principles", Accident Prevention Regulation BGV A1]:

Article 23: Protection measures (organizational measures or personal protective equipment) should be implemented in order to protect workers’ safety and health from weather conditions Available at: http://bibliothek.arbeitssicherheit.de/content/bgvr-53403a0bee4445c6a5da1b58a2f6533d/resource/content-cache-pdf

• Italy

Presidential Decree n. 303 of 19 March 1956 “General standards for occupational hygiene":

Article 22 addresses workers’ protection against artificial and natural UVR: "Workers must be also protected against UVR by wearing safety glasses, sunscreens and suitable clothing"

• Portugal

Portaria n.° 987/93 “Establece as prescrições mínimas de segurança e saúde nos locais de trabalho" ‘[“Legislation on the Minimum Provisions for Health and Safety in Workplaces"], Diário da República, Number 234 , Série I-B de 1993-10-06:

Article 7.3: “Windows, skylights and glazed partitions shall not allow an excessive solar exposure […]"

Article 7.4: “When necessary, protections shall be placed to protect workers against heat radiation sources such as pipes, heating system and others harmful heat sources".

Available at: http://dre.pt/gratis/1s/dr1gratis.asp

• Spain

Royal Decree 486/1997 on the Minimum Provisions for Health and Safety in Workplaces (Transposition of Directive 89/654/EEC), Official State Gazette (BOE) Number 97, 1997:

Article 7.2: “Exposure at work to physical, chemical and biological agents in the working environment shall be governed by the dispositions of the specific regulations".

Annex III. Environmental Conditions in Workplaces

1. “Exposure to environmental conditions in workplaces shall not represent a risk for the health and safety of workers.

2. Similarly, and as far as possible, the environmental conditions at workplaces shall not constitute a source of discomfort or inconvenience for workers. To achieve this, extreme temperatures and humidity, sudden changes of temperature, troublesome currents of air, unpleasant smells excessive irradiation and, in particular, solar radiation through windows, lights or glazed partitions shall be avoided."

Available at: http://www.insht.es/portal/site/Insht/menuitem.1f1a3bc79ab34c578c2e8884060961ca/?vgnextoid=e0b917815b2d5110VgnVCM100000dc0ca8c0RCRD&vgnextchannel=ff3cc6b33a9f1110VgnVCM100000dc0ca8c0RCRD&tab=tabConsultaCompleta

Risk assessment

The occupational risk related solar radiation changes from day to day and between hours of day together with changes of UV-Index. UV-Index reflects the degree of hazard from solar radiation and its values can be the base of risk assessment for a particular workday ^[11]. The results of risk assessment can be currently used to provide an adequate protection plan for a particular workday ^[12][13].

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).

Nevertheless, the UVI is a useful measure to appraise solar UVR and thus to prevent hazardous influence.

To be more precise, a risk assessment according to EN 14255-1:2005 „Measurement and Assessment of Personal Exposures to Incoherent Optical Radiation – Part 3: UV-Radiation emitted by sun" ^[14] should be carried out.

Beside the procedure of risk assessment using the solar UV-Index, this standard describes methods of calculation and assessment of skin and ocular exposure factors, methods of erythemal effective radiant exposure and non-melanoma skin cancer radiant exposure and sun protection measures.

An occupational disease is defined as a chronic ailment that takes place as a result of occupational activity. Only such diseases are adopted into the act, which are medically proven to be caused by a specific exposure. Further on, it is required that the disease is more prevalent in a body of workers than in the general public and in other worker populations.

Dealing with and compensation of occupational diseases is regulated very heterogeneously throughout Europe. Since 1990, a Commission Recommendation concerning the European schedule of occupational diseases is in effect, which has been last updated in 2003. It is divided into two parts: Part I lists ailments which should be adapted as occupational diseases in the national states of the EU; while listings in part II denote ailments with possible relation to occupational activity, and thus can be adopted to part I in future times.

Regarding UVR, only entry 502.01 “Conjunctival ailments following exposure to ultraviolet radiation" in part I relates to an occupational disease ^[15]. Neither non-melanoma skin cancer, nor other diseases are listed in part I or proposed in part II.

In Germany, the introduction of a new listed occupational disease regarding AK and SCC after exposure to natural UVR is imminent. From this time on, people suffering from AK and SCC can be compensated if procedural requirements are fulfilled.

Prevention is achieved best by raising the awareness of the people regarding the hazardous potential of UVR. Handouts and advertising in media ("social media"), nationwide or pan-European campaigns for protection against solar UVR help to find a better understand for what has to be done to protect the skin during working time or private time. However, protective measures may be taken for prevention.

Natural protective measures

Up to a certain level, the eyes are protected against too much irradiance from the sun due to the geometry of the eye socket. Mostly the eye view is horizontal or downwards, preventing from staring in the sun. Involuntary closing of the eye also reduces irradiance while looking into bright light sources.

The skin is able to tan upon exposure against UVR. Biologically, this is achieved by pigmentation and thickening of the horny layer. The “ultraviolet protection factor" of the skin has been subject to research. Data showed that the protection factor is maximal about 2.5 for Caucasian people ^[16], yielding only small protection in comparison to the risk. For example, if the un-tanned skin suffers from erythema after 10 min, the tanned skin develops erythema after 25 min. For outdoor-workers in the summertime, this is far too less.

Additional protective measures

Natural protection of the eyes and the skin is often not sufficient to protect from harm arising from solar UVR. Other methods, including technical, organizational and personal measures, can help to minimize the exposure:

• Avoiding high exposure against solar radiation: If possible, work plans should be such that no work in the bright sun has to be done at noon.
• Shadow should be provided, e. g. with cloth around a working place (“housing").
• Planning outdoor activities in such a way that people move along with the shadow.
• Wearing of suitable sun glasses, especially in regions with high albedo (e. g. snow, sand, water, large concrete areas).
• Wearing of suitable, skin covering clothing (e. g. long sleeves). It should be taken care that the clothing is intransparent.
• Wearing of suitable headwear, e. g. broad-brimmed hat. Some headwear includes the protection of the neck while working bent over.
• Usage of sunscreen: Skin areas that cannot be covered by clothing should be treated with sunscreen with a high protection factor. One should be aware that application of sunscreen has to be very precise and also to be repeated after 2 hours, roughly. The light protection factor denoted only resembles an estimate and is solely reached if 2 mg/cm² were applied. Sweating for example washes off sunscreen and so decreases the protection.