Evaluating potential spectral impacts of various artificial lights on melatonin suppression, photosynthesis, and star visibility

PLoS One. 2013 Jul 5;8(7):e67798. doi: 10.1371/journal.pone.0067798. Print 2013.


Artificial light at night can be harmful to the environment, and interferes with fauna and flora, star visibility, and human health. To estimate the relative impact of a lighting device, its radiant power, angular photometry and detailed spectral power distribution have to be considered. In this paper we focus on the spectral power distribution. While specific spectral characteristics can be considered harmful during the night, they can be considered advantageous during the day. As an example, while blue-rich Metal Halide lamps can be problematic for human health, star visibility and vegetation photosynthesis during the night, they can be highly appropriate during the day for plant growth and light therapy. In this paper we propose three new indices to characterize lamp spectra. These indices have been designed to allow a quick estimation of the potential impact of a lamp spectrum on melatonin suppression, photosynthesis, and star visibility. We used these new indices to compare various lighting technologies objectively. We also considered the transformation of such indices according to the propagation of light into the atmosphere as a function of distance to the observer. Among other results, we found that low pressure sodium, phosphor-converted amber light emitting diodes (LED) and LED 2700 K lamps filtered with the new Ledtech's Equilib filter showed a lower or equivalent potential impact on melatonin suppression and star visibility in comparison to high pressure sodium lamps. Low pressure sodium, LED 5000 K-filtered and LED 2700 K-filtered lamps had a lower impact on photosynthesis than did high pressure sodium lamps. Finally, we propose these indices as new standards for the lighting industry to be used in characterizing their lighting technologies. We hope that their use will favor the design of new environmentally and health-friendly lighting technologies.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Humans
  • Light*
  • Lighting / methods
  • Melatonin / metabolism*
  • Photosynthesis / radiation effects*
  • Plant Development / radiation effects


  • Melatonin

Grant support

This work was supported by Fond de recherche du Quebec - Nature et Technologie (FRQNT) Programme pour le dégagement d’enseignement des chercheurs de collège Regroupements stratégiques (http://www.fqrnt.gouv.qc.ca/) and Cegep de Sherbrooke - CERTEE (http://cegepsherbrooke.qc.ca). This work was partially supported by the Slovak National Grant Agency VEGA (grant No. 2/0002/12). This work was also partially supported by the Programme de soutien aux chercheurs et aux chercheuses du collégial from ministère de l’Enseignement supérieur, de la Recherche, de la Science et de la Technologie, Québec. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.