What is responsible for 90% of all skin cancers?

How Sun Exposure Causes 90% of Skin Cancers

Ultraviolet radiation (UVR) from the sun is the leading cause of skin cancer—accounting for about 90% of non-melanoma cases. Despite its invisible nature, UVR packs a powerful punch. It’s not just a summer concern; it’s a year-round threat.

The sun emits two primary types of ultraviolet rays that reach the earth: UVA and UVB. While both can damage skin, they do so in slightly different ways. UVA rays penetrate deep into the skin, contributing to premature aging and long-term damage to skin cells. UVB rays, on the other hand, are primarily responsible for sunburns. Both types play a role in altering the DNA of skin cells, setting the stage for cancer to develop over time.

Unlike other forms of radiation, UV radiation is classified as a proven human carcinogen by global health organizations. This means there’s no safe threshold—every unprotected exposure adds up. Whether it’s a day at the beach or just walking to your car, cumulative exposure to UVA and UVB rays increases your risk of developing basal cell carcinoma, squamous cell carcinoma, and even melanoma—the most dangerous form of skin cancer.

What makes this especially concerning is how common sun exposure is. Most people don’t realize that UV damage can happen even on cloudy days or through windows. And while sunlight helps the body produce vitamin D, the benefits don’t outweigh the risks when it comes to unprotected exposure.

The good news? Most skin cancers are preventable. Simple measures—like wearing broad-spectrum sunscreen daily, seeking shade during peak hours, and donning protective clothing—can drastically reduce your risk. Skin cancer may be widespread, but with awareness and smart habits, it’s largely avoidable.