Neonatal exposure to protoporphyrin-activating lighting as a contributing cause of childhood acute lymphocytic leukemia.

While being a relatively rare disease, acute lymphocytic leukemia (ALL) is the leading form of cancer in children in the developed world today. ALL sharply peaks in incidence at ages three to four years. In the United States there have been persistent, unexplained increases in incidence of ALL in the past two decades. We hypothesize that exposure to photosensitizing lighting immediately after birth may be a contributing cause of ALL. Fluorescent lamps and other light sources with strong illumination, around 400 nanometers, are protoporphyrin-activating. Activation of protoporphyrin produces superoxides and free radicals that can induce breaks in DNA. In newborn nurseries in the US, the intensity of lighting has increased five- to 10-fold over the past two decades. Thus, protoporphyrin-activating light may be a contributing cause of childhood ALL. Additional retrospective and prospective studies should be undertaken of the relationship between exposure of newborns to protoporphyrin-activating illumination and the development of childhood ALL, along with in vitro studies of the hematologic effects of fluorescent lighting. Protoporphyrin-activating lighting is clearly not the sole determinant of ALL, but it could be a completely preventable cause. Inexpensive plastic filters could reduce these exposures substantially.