Ballon Generali diameter of . It has been used as advertising billboard for Fortis, then from 2002 for Eutelsat. In 2008, a partnership has been signed with Banque populaire and Airparif : renamed "ballon Air de Paris", its internal illumination system changes the outer colour in real-time, according to the ambient air pollution in Paris, measured by Airparif : from green (good) to red (bad) through orange (poor). This system was completed by an independent lighting (panels light-emitting diode, visible especially at night on the lower part of the shell) stating the air quality near traffic with the same colour code. On
Light-emitting diode city-dwellers led to some controversy. So far high-pressure sodium lamps (HPS) with an orange light spectrum were the most efficient light sources commonly used in street-lighting. Now many modern street lamps are equipped with Indium gallium nitride LEDs (InGaN). These are even more efficient and mostly emit blue-rich light with a higher "correlated color temperature (CCT)". Since light with a high CCT resembles daylight it is thought that this might have an effect on the normal circadian physiology by suppressing melatonin production in the human body. There have been no relevant studies as yet and critics claim exposure levels are