Ultraviolet (UV) radiation is an invisible portion of the sun’s energy that includes both longer-wave UVA and shorter-wave UVB rays. While both types can cause damage, many people underestimate the risk during winter months. Snow reflects UV rays, and this reflection dramatically increases the risk of skin and eye damage. This is a serious concern because the light strikes the body from two directions simultaneously, doubling a person’s total UV exposure.
The Science Behind Snow’s Reflectivity
Snow exhibits a high measure of reflectivity, a property known as albedo, which describes the fraction of incoming light that a surface reflects. This high albedo is primarily due to the physical structure of snow. Each snowflake is a complex, multi-faceted ice crystal, and when millions accumulate, they form a matrix of surfaces and air pockets. This crystalline structure causes incoming sunlight to scatter in multiple directions. The scattering process, known as diffuse reflection, is highly effective across the entire solar spectrum, including the harmful UV wavelengths.
Quantifying the Reflected UV Radiation
Freshly fallen, clean snow can reflect a significant proportion of incident UV radiation, often ranging between 80% and 90% of the light that hits it. This reflection rate is dramatically higher than other common natural surfaces; for comparison, water reflects only about 5% of UV rays, while grass and soil reflect less than 10%. The high reflectivity means a person receives a “double dose” of UV exposure. Radiation strikes directly from the sun above, and simultaneously from the ground as the snow reflects it upward. This upward reflection exposes areas of the skin and eyes that are typically shielded, such as the underside of the chin and the lower eyelids.
Health Impacts of Dual UV Exposure
The combined effect of direct and reflected UV radiation poses a high risk for specific health consequences. For the skin, this dual exposure accelerates the process of sunburn and increases the risk of long-term skin damage. Reflected UV rays often hit the face from below, targeting the nostrils, ears, and under the chin, which are areas commonly missed during sunscreen application. The eyes face an acute condition known as photokeratitis, or “snow blindness,” which is like a sunburn on the surface of the eye. Symptoms often include a gritty feeling, pain, redness, and light sensitivity, typically not appearing until several hours after the exposure.
Essential Protective Measures in Snowy Environments
Mitigating the enhanced UV risk in snowy environments requires comprehensive protection for both the eyes and the skin. For eye protection, wear wrap-around sunglasses or goggles that block 99% to 100% of both UVA and UVB rays. The snug fit of wrap-around styles prevents UV radiation from entering the eyes from the sides or top, where reflection is most intense.
For skin protection, apply a broad-spectrum, water-resistant sunscreen with a Sun Protection Factor (SPF) of 30 or higher. Sunscreen should be applied generously to all exposed areas 20 minutes before going outside and reapplied every two hours, especially after sweating. Pay particular attention to applying sunscreen under the chin, beneath the nose, and behind the ears, as these spots are highly susceptible to the upward-reflected rays. Protective clothing, such as a high-collared jacket, a balaclava, or a hat that covers the ears, minimizes exposed skin.