Closer to the Sun: The Science Behind High-Altitude UV Exposure and Skin Cancer Risk
In Colorado’s high country, sunshine is part of the lifestyle. Whether you’re trail running above treeline or skiing Vail’s iconic Back Bowls, those bluebird days are why people love living and recreating in the mountains.
But there’s a downside to all that sunshine.
At high altitude, ultraviolet (UV) radiation is significantly stronger than at sea level. “Colorado has higher incidence of skin cancer because of greater UV exposure at elevation and a population that tends to enjoy being outdoors,” explains Dr. Alex Menter, a medical oncologist at the Centro de Cáncer Shaw.
No, you shouldn’t hide inside. Instead, play safer outside with these sun-smart strategies.
Thin Air, Strong Rays
When people think of high-altitude destinations, they often think about thinning air and gasping for breath. What many people don’t realize is that the same thinner atmosphere provides less protection from the sun’s harmful UV rays.
At 9,000 feet, UV radiation can be nearly twice as intense as it is at sea level. With less atmosphere to absorb and scatter UV rays, more radiation reaches our skin.
“Our body is always trying to repair itself faster than it can break down,” explains Dra. Melissa O’Meara, medical director of concierge medicine at Vail Health. “It does a pretty good job, but that can still leave us slowly accumulating damage to cellular DNA over many years. The more UV exposure we have, the harder our body has to work to repair the damage.”
While a sunburn may fade after a few days, the effects of UV exposure can linger much longer. Chronic exposure accelerates skin aging, contributing to wrinkles, loss of elasticity, dyspigmentation and cell death.
“Our cells use DNA as a blueprint that codes all the functions of the cell,” O’Meara says. UV radiation can damage DNA to the point that it can’t function properly. “Our bodies have systems to detect and repair these kinds of issues, but UV radiation can blunt those systems by causing inflammation and by locally suppressing the immune system.”
Know the Signs
Skin cancer is common, but early detection dramatically improves outcomes. There are three primary types:
- Basal Cell Carcinoma: Most common and slow-growing.
- Squamous Cell Carcinoma: Faster growing, but often highly treatable.
- Melanoma: The most aggressive and potentially dangerous form.
Early detection is one of the best ways to protect your health. If you notice a suspicious spot, see your health care provider and get checked.
Menter recommends regularly checking your skin and using the ABCDE Rule to identify possible signs of melanoma:
- A = Asymmetry: One half doesn’t match the other.
- B = Border: Edges are uneven or irregular.
- C = Color: Multiple colors or uneven coloring.
- D = Diameter: Larger than a pencil eraser.
- E = Evolving: Changing in size, shape or color.
For mountain residents and outdoor enthusiasts, annual skin checks should be considered part of routine preventative care.
The Snow Effect
Many people are diligent about sunscreen in July but forget about it in January. That’s a mistake.
“Cloud cover reduces more of the visible light spectrum than it does of the UV spectrum. This means that a cloudy day will look dark to you, but it may still have a significant amount of UV radiation,” O’Meara explains.
Menter offers a simple rule of thumb: “If you can still see a shadow, then you’re getting UV exposure.” That means it’s time to cover up.
Winter brings an additional challenge. Snow reflects UV radiation at you like a giant mirror. Snow and ice can reflect up to 85% of UV rays, effectively exposing you from above and below.
The takeaway? UV exposure is a year-round concern in the mountains, not just a summer one.
Smarter Protection
Avoiding the outdoors isn’t the answer. Time outside supports physical health, mental well-being and an active lifestyle. The goal is to learn how to enjoy the mountains while reducing your skin cancer risk at altitude. Experts recommend a layered approach to protection.
“Be mindful of when peak UV times are. Morning and late afternoon sunshine pose a reduced risk of burning,” Menter explains. “Think of the UV index to prevent burns and make sure you’re using sun protection.”
A few simple habits can make a significant difference:
- Use broad-spectrum (UVA & UVB) SPF 30 or higher sunscreen.
- Reapply every two hours.
- Don’t forget lips, ears, hands and the back of the legs.
- Choose wide-brim hats and UV-blocking sunglasses when possible.
- Seek shade during peak hours.
Another highly effective strategy is UPF clothing. Unlike sunscreen, UPF-rated fabrics don’t need reapplication and you’ll cover those hard-to-reach spots on your back. Sun hoodies and neck gaiters have become increasingly popular for runners, cyclists and hikers who like to spend long hours outdoors.
A Lifetime Investment
Most mountain residents wouldn’t skip exercise, annual checkups or a healthy diet. Skin health deserves the same level of attention, so prioritize year-round sun protection.
The reality is that sun damage accumulates over decades, but small daily habits can have a meaningful impact on long-term skin health. Your future self, and your skin, will thank you.
