Climate change and the risk of UV-related diseases

UV radiation is the cause of immediate and long-term effects on the skin and eyes. It is the main cause of skin cancer, the most common form of cancer in fair-skinned people worldwide and the most onerous consequence of excessive UV radiation exposure in addition to cancer of the eyes and UV-related cataracts. Natural and artificial UV radiation is assigned to the highest risk group – group I, “carcinogenic to humans” – by the International Agency for Research on Cancer (IARC).

Scin cancer risk

Over recent decades, there has been a steady increase in cases of skin cancer caused by UV radiation According to the oncological S3 guideline “Prevention of skin cancer”, the incidence of non-melanoma skin cancer – that is, the number of new cases of the disease per 100,000 people per year – has quadrupled (in men) to quintupled (in women) in Germany over the last 30 years. According to the Robert Koch Institute, the incidence of malignant melanoma has quadrupled since the 1970s. According to extrapolations from the data of the Schleswig-Holstein skin cancer register, which in contrast to the data of the Robert Koch Institute also includes in-situ melanoma and in-situ squamous cell carcinoma, over 300,000 people are currently newly diagnosed with skin cancer every year and over 4,000 people die from it each year. In terms of both hospital treatments and deaths, the Federal Statistical Office reports a significant increase over a 20-year period.

Due to the influence of climate change on the stratospheric ozone layer, on temperature and on people’s behaviour, this situation is in danger of getting worse – not only for skin cancer caused by UV radiation but also for all acute and long-term health consequences of UV.

Scientific assessments show that, with a 1% depletion of the stratospheric ozone layer and the resulting increase in UV radiation, the skin cancer rate (incidence) may increase:

• by 1–2% for malignant melanoma,
• by 3–4.6% for squamous cell carcinoma and
• by 2.7% for basal cell carcinoma.

Estimates that assume complete adherence to the Montreal Protocol (the ban on ozone-depleting substances) and that take account of skin type have shown that, by the end of the 21st century, stratospheric ozone loss can be expected to lead to 90 to 100 additional cases of skin cancer (all UV-related types of skin cancer) per million inhabitants per year in the Mediterranean region and 30 to 40 additional cases per million inhabitants per year in Western Europe. In Germany, this would equate to some 2,500 to 3,300 additional skin cancer cases per year for a population of around 83 million.

Source: Christoph Burgstedt/Stock.adobe.com

With regard to temperature increases due to climate change, scientific model calculations have shown that a 2 °C global rise in ambient temperature and the associated changes in climate, which could result in intense heat and heatwaves at the regional level, could cause an 11% increase in the incidence of skin cancer by 2050. This estimate is supported by studies at the cellular level, which show that heat – or rather thermal stress in cells exposed to UVB radiation – inhibits the programmed cell death of UV-damaged cells in a number of ways, such that these cells survive for longer and more cells therefore remain in the skin that could subsequently degenerate into skin cancer cells.

Erroneous behaviour leads to increased risk

In addition to measurable changes in UV irradiance due to ozone loss and greater hours of sunshine, another significant risk factor for increasing UV-related diseases due to climate change is the “UV exposure pattern” – in other words, how much UV radiation people expose themselves to for how long and in what way. People who spend a lot of time in the sun, such as people who work outdoors, are at greater risk of developing skin cancer. Sunburns following excessively long periods of UV exposure or exposure to excessive UV intensities lead to an approximately twofold increase in the risk of malignant melanoma at every age – and a twofold to threefold increase if they occur during childhood.

As UV-related diseases – and especially UV-related cases of cancer – already have a lasting impact on the wellbeing of the individual and on the healthcare system as a whole, due to rising costs, determined action must be taken to prevent any exacerbation of this situation due to climate change. This can be achieved by adopting effective precautionary (preventive) measures. Precautionary measures to prevent UV- and heat-related diseases should therefore form an integral part of strategies to adapt to the health impacts of climate change. This is also recommended as a high priority in the oncological S3 guideline “Prevention of skin cancer”.