Beware of UV radiation

Today's indication says that there's a slight danger when exposing yourself into UV radiation.
The fact is that in certain altitudes here you have to use sunblock filter 50. Every 2 hours.
The average level of UV radiation which is not harmful  for your skin is under 10. Here in San Pedro de Atacama it's over 20. In this case we can't say: it CAN produce cancer but it actually PRODUCES cancer. And no joke about it.
I guess some tourists are not aware of it.