All concrete collapsing, massive drops/increases in pressure that can shatter your eardrums, untreated metals cold welding, full UV rays going through an Ozone layer that no longer exists, planes fall out of the sky… oh and yeah the Earths mantle just fucking collapsing in on itself and essentially dissolving as its composition has an enormous amount of oxygen
I am not the one who made the initial claim, but if you want numbers: about 2 % of sunlight is a shorter wavelength than UV-B or about 70 W/m². If you want the same irradiance from a lamp, all you need to do is get closer, unless the lamp is really weak. 5 seconds is simply nothing.