Does Smog Block UV? What a Hazy City Sky Really Does to Your Skin
When the sky turns gray-brown with haze, it's tempting to think UV is taking the day off - the science says don't bet your skin on it.
Aerosols and haze scatter and absorb some UV, modestly reducing ground-level intensity, but the effect varies by aerosol type and never reliably protects skin.
Atmospheric research published in Science shows that aerosols influence how much solar UV reaches the ground, but the effect is variable and tied to the type and amount of pollution rather than a dependable shield.
Questions we get a lot
Does haze or smog reduce how much UV reaches my skin?
It can reduce ground-level UV modestly, because aerosols scatter and absorb part of the incoming radiation. However, research in Science shows the effect varies by the type and amount of aerosol, so it is unpredictable. Enough UV typically still gets through to damage skin.
Can I skip sunscreen on a hazy, polluted day?
It is not a safe bet. While haze may cut UV somewhat, the reduction is variable and not reliable enough to count on for protection. Use the UV index rather than how hazy the sky looks to decide whether you need sun protection.
Why does the effect of aerosols on UV vary so much?
Different aerosols absorb and scatter UV to different degrees depending on their composition and concentration, as documented in atmospheric research published in Science. That means two hazy days can let through very different amounts of UV. Because of this variability, haze cannot be treated as a consistent form of sun protection.
r/SkincareAddiction: 'The air quality is awful and the sky looks brown today - can I skip sunscreen since it's so hazy?'