October 2, 2014…The International Energy Agency’s (IEA) Energy Efficient End-Use Equipment (4E) Annex on SSL (SSL Annex) published its final report on the human health issues related to solid-state lighting. The SSL Annex began to review all of the major health-related literature associated with LED lighting in 2011 to prepare a literature review for policy makers. The SSL Annex study was to determines whether or not SSL products are at least as safe as the products they intend to replace.
“Over the last several years, the SSL Annex conducted a study of the published literature of SSL on human health,” said Dr. Peter Bennich, chairman of the SSL Annex’s Management Committee and representative of the Swedish Energy Agency, one of the Annex’s member countries.“The study evaluated electrical risks, exposure to electromagnetic fields, glare, photobiological hazards, light flicker and non-visual effects of light. It provides a detailed review of these topical areas, and thereby gives decision makers important information that they can apply in the policy context of LED lighting.”
The report concluded that compliance with existing international electrical safety standards appropriately addressed electrical safety standards. The SSL Annex found that exposure to electromagnetic fields from SSL products is not a critical issue. The magnitude of electromagnetic fields from solid-state lighting was generally found to be much smaller than that of discharge lamps or certain household appliances.
Glare was recognized as a potentially critical issue in SSL products. The research suggests that the maximum luminance of the SSL finished products be specified, whether the products incorporate visible LED point sources or not. If the light source is diffused, the report suggests that the glare be calculated using the CIE’s Unified Glare Rating (UGR). However, the report says that the UGR is not an adequate measurement when there are point light sources that are are not diffused. In such cased the report recommends using the still imperfect, but better than UGR, French standard on visual ergonomics NF X 35-103.
For outdoor lighting that is sufficiently far away from the viewer from whatever light source and with installations such as stadium lighting, the glare index can be used to calculate disability glare. For street lighting the threshold index, which quantifies the reduction in visual contrast that the veil luminance causes, can be used to estimate disability glare. There is not one measurement calculation which accurately estimates glare. However, there are formulas for estimating glare with certain applications which should be used despite being imperfect.
In terms of safety of SSL, the standard CIE S009 / IEC 62471 safety assessment should be applied to all SSL devices. Additionally, LED manufacturers should follow the guidelines of IEC TR 62778 to categorize the risk group of the product.
The report notes that flicker (the modulation of the light source’s output) can cause discomfort or in limited cases even induce seizures in patients who suffer from photosensitive epilepsy. LED luminaires displayed a wide range of flicker values from zero flicker to a maximum of 100 percent. The report recommends that that the health effects of flicker be studied further so that the maximum flicker limit can be set for SSL products.
The report notes that all light sources deliver a wide range of non-visual (physiological effects) that should be taken into account in lighting system design. The physiological effects of lighting especially that of tunable LED lighting warrants further studied.
“LEDs are very flexible in terms of emission spectrum, ranging from coloured light to white light. As a consequence, LED devices are now used by physicians to treat certain conditions by controlling the non-visual effects of light – called phototherapy” said Dr. Christophe Martinsons of the Centre Scientifique et Technique du Bâtiment (CSTB) in France, and lead author of the report. “And in the future, combining both a better understanding of the non-visual effects of light with the availability of spectrally tunable LED devices, should result in applications of phototherapy for the treatment of health conditions.”
The report concluded that compared to other lighting technologies, SSL technology is not expected to have more direct harmful physiological effects. However, the report says that SSL may indirectly increase a person’s overall daily light exposure. Thus, a dark, nocturnal environment is recommended at night for sleeping while maintaining a suitable exposure level during daytime through a combination of daylight and artificial lighting.