Implication for photosensitive patients of ultraviolet A exposure in vehicles.
Level 5 - mechanism / opinion, no new human data
Bench optical transmission experiment without human clinical data
PubMed 15491429 · doi:10.1111/j.1365-2133.2004.06098.x
What was done
The investigators measured the percentage transmission of UVA radiation through a selection of automotive glass samples, comparing laminated versus nonlaminated glass and different color tints. They calculated the time required to transmit 5 J cm(-2) of UVA—a dose sufficient to trigger polymorphic light eruption (PLE) in susceptible individuals—through different glass types.
What was found
Laminated glass transmitted less UVA than nonlaminated glass, and tinted glass transmitted less UVA than clear glass. Nonlaminated clear glass transmitted the highest percentage of UVA at 62.8%, delivering a 5 J cm(-2) dose in 30 minutes. Grey laminated glass transmitted the lowest percentage at 0.9%, requiring 50 hours to transmit 5 J cm(-2).
Why it matters
Standard car side windows allow sufficient UVA transmission to trigger disease flares in photosensitive patients during routine travel, supporting recommendations for laminated or tinted glass, protective clothing, or behavioral adjustments.
Limits
This was an optical measurement study with no direct patient testing or measured clinical flare rates. The abstract does not state the number of glass samples tested, nor the specific solar irradiance conditions or angles of incidence used to calculate the exposure times.
Cited by
- supports Window glass blocks almost all UVB radiation while allowing UVA radiation to pass through.