Ultraviolet radiation (UV) is one of the most important risk factors for the skin. Non-melanoma skin cancer, which mainly consists of basal cell carcinoma (BCC) and squamous cell carcinoma (PCC), is common in the general population. It is believed that 65-90% of all forms of skin cancer can be caused by exposure to UV radiation. Other important factors are skin type and family history.
According to the ILO (International Labor Organization), of a global workforce of three billion, approximately 500 million people work outdoors for long periods. This makes it plausible that a work-related cause can be found for a significant proportion of the annually diagnosed forms of non-melanoma skin cancer. But to prove this, it is necessary to determine the exposure with sufficient certainty. This can often only be done on the basis of self-report, which entails all kinds of uncertainties.
German researchers have therefore set up a study with the aim of developing a globally usable matrix for exposure to UV radiation in occupations and to show how and for what purpose it can be used. It was for this project GENESIS-UV (GENeration and Extraction System for Individual expoSure) measurement system developed. This allows long-term measurements to be carried out with a number of variables in order to arrive at useful results. The system is robust, logs the data, is easy to use and easy to carry around in the work. It measures the UVA and UVB/C radiation every second.
A total of 1000 people participated in the measurement campaign. They wore the device during work for 7 months from April to October in the years 2014-2020. With this, 3,7 billion exposure datasets have been collected. For each participant, the occupational activity was defined using individual activities and work tasks. This made it possible to create 250 different professional profiles and 650 individual activities.
The data is stored in a freely accessible database that contains measurement data on UV exposure for 250 professions in half-hourly values, daily averages and extrapolated data for a year. The relevant activity profiles are also displayed. See https://egenesisauswertung.ifa.dguv.de.
It appears that exposure to UV differs per occupation, with not only the agricultural sector and the construction industry showing high exposure levels. Moreover, professions within these sectors still differ considerably. The specific position and work tasks therefore determine exposure more than the occupation. This also means that prevention should focus on the activities with the highest exposure rather than general advice.
The ability to stay out of the direct sun varies quite a bit: where a dock worker who lashes wood on trains is in full sun, his colleague who lashes containers on ships can often work in the shade. Their exposure therefore differs by a factor of nine.
The influence of the time of day can be seen, for example, with the employees of the day care centre. Those who work with children under the age of three have half as much sun exposure as those who work with children over the age of three. That's because the younger children take an afternoon nap indoors in the heat of the day, while the older children (and their supervisors) are already outside.
The sensitivity to UV radiation is related to the skin type, which is classified according to the Fitzpatrick scale. The scale ranges from skin type I (light skin, red hair, does not tan) to skin type VI (highly pigmented dark brown, does not burn). This classification is linked to a permissible dose to start of combustion: minimum erythemal dose (M.E.D.). For example, people in North America and Europe have predominantly skin types II and III with MED of 2-3 SED (SED is standard erythemal dose; 1 SED corresponds to 100 J per square meter of erythema-weighted radiation). However, there are currently no agreed or legal exposure limits for UV radiation, only recommendations.
Crossing the threshold
The number of readings for each occupation that exceed an exposure level in relation to the total of measured readings provides important information about the prevention of potential skin damage due to occupational exposure to UV radiation from the sun. The higher the percentage of exceedances, the greater the chance of damage in the future. This approach has been described for occupational health care (Wittlich, M. 2022). An exposure level has been established for each skin type that, if exceeded, increases the risk of skin cancer. Epidemiologically it has been calculated that for temperate latitudes (around 50° N/S) the risk of non-melanoma skin cancer doubles when the risk value is exceeded by 40%. It allows to identify the professions where preventive measures are needed.
It is clear that the risk varies greatly by skin type. People with light skin that does not tan quickly run a double risk in all kinds of professions. They will already have to protect themselves (hat, long sleeves, sun cream, etc.) if they work outside the home for less than two hours. However, those who work less than an hour a day outside the home during the year do not have an increased risk of skin cancer, although the time spent outdoors may probably be shorter in summer and longer in winter.
Influence of tasks and activities
Although exceeding the risk value is usually indicated for UV radiation over a year, the exposure strongly depends on the season. With skin type II, the MED of 2-3 SED will be exceeded in almost every profession on certain days in the summer. It can be helpful to look at the activity or task level to see where the greatest risks lie. The tasks of bricklayers mentioned in the article clearly show this. Task variation in relation to the time of day can limit exposure here.
Need for sunlight
It is good to realize that the maximum exposure to UV radiation often occurs early in the year, well before the meteorological maximum in June. This is a result of the human need for sunlight in the spring. We then want to spend more time outside in the sun. This does not mean that it is not important to prevent high exposure in the other summer months. The distribution of exposure over the day is important for each profession, whereby building in more moments in the shade (lunch, drinking breaks, working on the shaded side) can reduce exposure.
Skin cancer caused by UV radiation is a worldwide problem. It is therefore important to make the data and findings relevant for other countries as well. Latitude factors can be used for this: they describe the increase in radiation as we move closer to the equator from a geometric perspective. The article provides insight into the distribution of radiation levels across latitudes and how this affects the distribution of radiation levels over the year. The database includes a tool to extrapolate the data from Germany to other locations in the world.
Applying latitude factors also shows that the number of days the risk value is exceeded can increase significantly at lower latitudes. This also applies to the darker skin types (III and IV). While for light-skinned people in the Mediterranean region almost every occupation outside the home is risky, it appears that people with type III and IV cannot be outside indefinitely in that region either. For them, the limit is two and four hours respectively if they want to limit their risk of skin cancer.
Outside not discredited
In the discussion, the authors emphasize that the article and the data they have collected are not intended to discredit anyone outside of it. It is a plea to spend time outside, because it is possible to protect yourself from the risks. Outdoors people are more active with a positive health effect and sunlight also plays an important role in the production of vitamin D.
Prevention from early spring
Promoting prevention and awareness of UV radiation in our temperate latitudes should start early in spring, with a special focus on light-skinned people. Occupational health care must pay attention to the prevention of excessive exposure to UV radiation during the period April – October. The specific information about professions and activities can be a valuable guideline in this respect. If you delve deeper into the database, you will see that professional profiles often contain sub-profiles in which the exposure can differ greatly.
German occupational cancer of the skin
In Germany, occupational skin cancer is reported relatively well by a funding system. There are approximately 6500 cases of UV radiation-related non-melanoma skin cancer every year. Of these, 2500 come from the agricultural sector. Subsequently, there are many cases from the construction industry, where bricklayers are an important group, followed by earthworkers and roofers. The first occupation outside these sectors is the waste management and recycling workers.
Marc Wittlich, Stephan Westerhausen, Benjamin Strehl, Helmut Versteeg, Wiho Stöppelmann, The GENESIS-UV study on ultraviolet radiation exposure levels in 250 occupations to foster epidemiological and legislative efforts to combat nonmelanoma skin cancer, British Journal of Dermatology, 2022;, ljac093, https://doi.org/10.1093/bjd/ljac093
Wittlich, M. (2022). Criteria for occupational health prevention for solar UVR exposed outdoor workers-prevalence, affected parties, and occupational disease. Frontiers in public health, 9, 2328.