Formation of Photoproducts Lethal for Human Cells in Culture by Daylight Fluorescent Light and Bilirubin Light

Irradiation of Dulbecco's modified Eagle's tissue culture medium with “Daylight,”“Special Blue,” or “Bilirubin” fluorescent light produces photoproducts lethal to human cells. Killing is abolished when (1) riboflavin, (2) tryptophan and tyrosine, or (3) riboflavin, tryptophan and tyrosine are deleted from medium prior to irradiation with any of the above fluorescent lamps. Toxic photoproducts are also formed when buffered salt solutions containing (a) riboflavin and tryptophan, (b) riboflavin and tyrosine, or (c) riboflavin, tryptophan and tyrosine are exposed to any of these light sources.