UV protection in the mountains: the underestimated risk

The atmosphere is your natural UV filter, and that filter gets thinner with every metre of altitude. The thinner layer of air absorbs and scatters less UV radiation, while the biologically most harmful short-wave UVB levels increase disproportionately.

The pioneering study by Blumthaler et al. (1997) produced the measurements still cited most frequently today. Under clear-sky conditions, researchers measured the following between Innsbruck (577 m) and Jungfraujoch (3,576 m):

• Total radiation: +8% per 1,000 metres of altitude
• UVA radiation: +9% per 1,000 metres of altitude
• Erythemally effective UVB radiation: +18% per 1,000 metres of altitude
• Short-wave UVB (300 nm): +24% per 1,000 metres of altitude

In practical terms, at 3,000 metres you are exposed to 36–54% more sunburn-causing UV radiation than at sea level. Combined with snow reflection, the effective dose can double or triple.

The surface you move across has a major influence on your UV exposure. The review study by Turner & Parisi (2018) compiled all available UV albedo measurements for natural surfaces, and the findings make clear why snow plays a special role.

Fresh, dry snow reflects up to 94% of UV radiation, amounting to an almost complete doubling of exposure. Even old, dirty snow still reaches 59%. By comparison, grass reflects just 2% and water 3–5%.

One effect that is often underestimated: radiation reflected by snow reaches the body from below, hitting areas that usually receive very little UV, including the chin, nostrils and beneath the eyebrows. A 3D model by Feister et al. (2016) showed that in snow-covered mountains, UV exposure across the whole body rises by 10% per 100 metres of altitude, significantly more than the altitude effect alone.

The evidence is clear, and sobering. Outdoor athletes have a measurably higher risk of skin cancer and its precursors. Three groups have been particularly well studied: mountain guides, marathon runners and people living at high altitude.

The dosimetry study by Moehrle et al. (2003) produced alarming figures: nine mountain guides wore UV dosimeters for one year. Their average daily dose exceeded the occupational exposure limit sixfold, while peak values were as much as 23 times higher.

The consequences are measurable. Zink et al. (2016) examined 62 mountain and ski guides in southern Germany: 43.5% had skin cancer or precursors (primarily actinic keratoses). Almost half had never seen a dermatologist. In a follow-up study (2018), mountain guides had a 2.6 times higher risk of skin cancer than farmers, despite farmers also working extensively outdoors.

A study at the Medical University of Graz (Ambros-Rudolph et al., 2006) compared 210 marathon runners with a control group. The runners had significantly more atypical moles and sunspots, both of them melanoma markers.

Particularly revealing: Richtig et al. (2008) found an average of 19.6 sunspots on exposed areas (shoulders) and not a single one on covered areas (buttocks). Training intensity correlated directly with the number of melanoma markers. The harder the training, the more skin changes occurred.

96.7% of marathon runners trained in shorts, but only 56.2% used sunscreen regularly. Among trail runners, 66.5% reported sunburn during training.

The first head-to-head comparison study of UPF clothing and sunscreen was conducted in 2022 by Berry et al. at Oregon Health & Science University (OHSU). The result was clear: UPF clothing outperforms sunscreen across all measured parameters.

UPF textiles blocked more than 99% of UVB and 96–98% of UVA radiation. SPF 30 sunscreen achieved 76% UVB protection when applied at the optimal amount, while SPF 50 reached 94%. Under real-world conditions, where people typically apply only half the recommended amount, the gap is even greater.

Limitation: Not all UPF clothing retains its protective effect over time. A 2023 Cureus study found that two of the seven brands tested lost 70–78% of their UPF rating after 50 wash cycles. These brands relied on nano-zinc additives rather than the fabric structure itself. Clothing with UV protection from densely woven polyester or fibres spun into the fabric retains its effectiveness better than chemically treated textiles.

What to look for when buying:

• Certified UPF 50+ (blocks >98% of UV radiation)
• Choose fibre-based protection where possible (dense polyester, not just a chemical finish)
• Sweat- and water-resistant construction
• Ventilation zones for comfort during sport

The scientific consensus is clear: use UPF clothing as your base protection and sunscreen on uncovered skin. This combination provides the best overall protection, without application errors and with minimal effort. Here is your practical plan.