Which UV radiation is primarily associated with aging?

UVA radiation is primarily associated with skin aging due to its ability to penetrate deep into the skin layers. This type of UV radiation accounts for approximately 95% of the UV radiation that reaches the Earth's surface, and it has a longer wavelength compared to UVB and UVC.

UVA radiation can lead to the breakdown of collagen and elastin, which are crucial for maintaining the skin's structure and elasticity. This process contributes to the formation of wrinkles, fine lines, and other signs of aging such as loss of firmness and pigmentation changes in the skin. Moreover, UVA rays are often present during all daylight hours and can penetrate through windows, making people susceptible to their effects even indoors.

In contrast, UVB radiation can cause sunburn and has a more direct impact on skin cancer risk, while UVC radiation is largely absorbed by the Earth's atmosphere and does not reach the surface. Visible light is part of the light spectrum we can see and is not categorized under UV radiation; thus, it does not have the same damaging effects on skin aging as UVA.