Kid something that you have to realize is that there are a number of different kinds of UV rays,,,they are all not created equal and the sun provides one kind and the bulbs that we use are a different kind, UV-C
======================================
UV-C - Shortwave UV, that includes germicidal ultraviolet - 253.7nm wavelength - used for air, surface and water disinfection. Unintentional overexposure to UV-C causes skin redness and eye irritation, but does NOT cause skin cancer or cataracts.
UV-B - A small, but dangerous part of sunlight. Most solar UV-B is absorbed by the diminishing atmospheric ozone layer. Prolonged exposure could result in unhealthy effects on the skin and eyes.
UV-A - Long wave UV, also known as blacklight, responsible for skin tanning, generally not harmful, used in medicine to treat certain skin disorders.