Which UV ray is primarily responsible for skin aging and tanning?

UVA rays are primarily responsible for skin aging and tanning. These rays penetrate the skin more deeply than UVB rays and can damage collagen and elastin fibers, which leads to premature aging signs such as wrinkles and loss of skin elasticity. Additionally, UVA rays are primarily associated with the tanning process as they stimulate melanin production in the skin, resulting in a darker skin tone. Unlike UVB rays, which are more intense and primarily responsible for sunburn, UVA rays have a more constant level of intensity throughout the day and throughout the year, increasing the chances of prolonged skin exposure and damage. UVC rays are mostly absorbed by the Earth's atmosphere and do not significantly reach the skin under normal circumstances, which is why the focus is on UVA in the context of tanning and aging.