[Hazards posed by LEDs? : A comparative study]

The increasing use of light-emitting diodes (LEDs) for lighting applications and displays is giving rise to public and professional concern that blue LED emissions could damage the retina or via the proven influence on the melatonin levels disrupt the human day-night rhythm.

The study aimed to measure the emission of LEDs and other relevant light sources and evaluate the results comparatively with the help of suitable evaluation functions in order to recognize whether LEDs differ considerably from other light sources in their hazard potential.

The spectra of a cold white and a warm white LED, a white tablet LED display, a fluorescent tube and a halogen lamp were measured and evaluated together with a sunlight spectrum relative to each other using the blue light hazard retina weighting function and the circadian action function.

Since LEDs can be very different, relative LED ratings also vary greatly. The warm white LED is the one with the lowest risk of blue light retinal damage and the lowest potential for inhibition of melatonin formation and in this respect even gentler than halogen lamps. For cold white LEDs, the values for photochemical retinal danger as well as for the expected inhibition of melatonin formation are much greater. The values for the tablet LED display are even higher.

Not only LEDs but all examined light sources emit in the blue spectral range, so that in principle they represent a retinal hazard. Depending on the employed LED type, this hazard may be greater or less compared to conventional light sources but even cold white LEDs are rated slightly better than sunlight at noon. To support consumers it might be helpful to classify LEDs and other illuminants by their potential hazard to the eye, as they are already labelled with respect to their energy efficiency.