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Dueling studies

Unfortunately there is lack of conclusive data on the impact of white light at night. Just how bad is such light for us at night, and how much does it take to adversely impact humans and animals?

Last year, the Lighting Research Center (LRC) at Rensselaer Polytechnic Institute (RPI) published a paper on the impact of lighting on the circadian system as part of its Alliance for Solid-State Illumination and Technologies (ASSIST) series. That research found that typical night-time exposure to white light could suppress melatonin, but at a level far below the 15% threshold that the LR researchers consider problematic. The LRC research was based on a 20-year-old person exposed to light in a typical outdoor scenario for one hour.

The LRC study came after a number of environmentalists had raised concerns over night lighting with a prevalence of blue wavelengths. Indeed the International Dark-Sky Association (IDA) had campaigned vigorously against broad use of LED sources. The IDA had raised health concerns as an issue although they clearly have many members that are more worried about recreational endeavors such as astronomy.

The IDA has subsequently worked with the SSL and general-lighting industry developing the Model Lighting Ordinance (MLO) to help communities set reasonable standards for night-light levels. The MLO accepts SSL as perfectly acceptable although it does set standards for color temperature and more importantly strictly limits up-light pollution and unacceptably high levels at ground level.

Given developments such as the MLO, the timing of the new study is bit surprising given that most outdoor SSL installations get positive marks in all areas other than upfront costs. But the authors of the paper have strong words about future SSL products.