A process for damaging and maintaining damage to the nucleic acids of pathogens such as white blood cells, bacteria and viruses which may be contained in blood or blood components. This process comprises adding to the blood or blood component containing pathogens an effective amount of riboflavin, and exposing the fluid to light of an appropriate wavelength to damage the nucleic acid of the pathogen and to substantially maintain the damage to the pathogenic nucleic acids to allow for subsequent transfusion into a recipient.