What percentage of a typical American's lifetime exposure to ultraviolet radiation occurs before age 20?

The correct response highlights that a significant proportion of an individual's lifetime exposure to ultraviolet (UV) radiation, specifically around 80%, occurs before the age of 20. This statistic underscores the importance of sun safety measures during childhood and adolescence when skin is more susceptible to UV damage due to its thinner and more delicate nature.

The rationale behind this figure is that early life is typically characterized by increased outdoor activity, which means more time exposed to sunlight. Additionally, behaviors established during these formative years, such as spending time outdoors without adequate sun protection, can lead to prolonged exposure. Since most skin damage from UV rays accumulates over time, a substantial amount of this cumulative exposure is concentrated in these early years, which can substantially increase the risk of developing skin cancer later in life.

Understanding this makes it clear that proactive measures, such as using sunscreen, wearing protective clothing, and seeking shade, are crucial during youth to mitigate long-term health effects related to UV radiation.