Which factor significantly increases risk when exposed to ultraviolet radiation?

The factor that significantly increases the risk when exposed to ultraviolet (UV) radiation is skin type. Individuals with lighter skin types have less melanin, the pigment that provides some level of natural protection against UV radiation. As a result, those with fair skin are at a heightened risk for sunburn and skin damage, which can lead to skin cancer over time.

Skin type also influences how the body responds to sun exposure. People with lighter skin often burn more easily than those with darker skin, which has more melanin and offers greater protection against the harmful effects of UV rays. This inherent difference in skin pigmentation is a critical factor in determining an individual's vulnerability to the adverse effects of UV exposure, reinforcing why skin type is a significant risk factor in assessing UV-related harms.

While other factors mentioned can influence exposure levels or susceptibility, skin type remains a primary determinant of risk in relation to UV radiation.