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Office of Technology Assessment at the German Bundestag Office of Technology Assessment at the German Bundestag

Information on the project

Light pollution – extent, societal and ecological impacts as well as approaches

Thematic area: Energy, resources, environment
Analytical approach: TA project
Topic initiative: Committee on Education, Research and Technology Assessment
Status: ongoing
Current project phase: Preparation of external expertise
Duration: 2017 till 2018

Thematic background

The establishment of electric light sources in the 1880s entailed substantial changes and progress with regard to people’s way of working and living. The spread of artificial light sources continuing since then, however, gives more and more importance to an unintended consequence of this development – the so-called light pollution. This term describes the brightening of the night sky by artificial light as an unwanted side effect of private and public lighting of streets, paths in parks and watersides, decorative or commercial illumination or light art. Particularly above large cities, so-called light domes evolve which are ever expanding in the course of urbanisation and rural sprawl.

In recent years, there has been an increasing number of scientific studies dealing with the topic of light pollution. The partly negative biological, ecological, health-related, sociocultural and economic impacts of artificial lighting at night are examined in various disciplines.

  • Human health: With regard to health, the main problem is that the exposure to light is reduced during the day, but increased at night – thus impacting the natural dark and rest phases. The substantial exposure to artificial light has an impact on human biological rhythms entailing possible consequences for physical and mental health. This might include e. g. stress or hormonal effects (possibly with an increasing risk of cardiovascular diseases and cancer).
  • Flora and fauna: Light pollution might involve disturbances of the living conditions and behaviours e. g. for nocturnal insects or migratory birds, as their orientation at night might be impaired due to artificial light sources. For plants as well, there are indications for impacts of light pollution in the form of early blooms or delayed winter dormancy.
  • Economic and sociocultural consequences: Very often, light pollution is caused by inefficient lighting technology which, in turn, involves consequential costs for society due to an excessive energy demand. Sociocultural impacts of light pollution are the visual disappearance of the starry sky due to sky glow and the impairment of terrestrial space research.

Currently, the developments regarding lighting technology and lighting design as well as the mass availability of light-emitting diodes (LEDs) for lighting purposes open up a window of opportunity for new technical and creative solutions: Due to their focusability and digital controllability, LED products offer the potential to reduce scattered light in a targeted way and to save significant quantities of energy compared to conventional light bulbs. At the same time, however, LED lighting also bears new risks with regard to light pollution, i. a. due to the high share of blue in the light spectrum – the implications of which still remain widely unknown for flora, fauna and human health. Moreover, new trends in urban lighting design, the lighting industry and in standardisation procedures at the national and European level offer approaches to reduce the trade-offs between the objectives and unwanted consequences of artificial lighting.

Objectives and approach

Public awareness of light pollution and its implications is growing. Citizens are becoming increasingly involved in so-called dark-sky initiatives and in citizen science projects. With regard to politics as well, the topic is becoming increasingly relevant. Though, in Germany, there are currently no binding limit values for light immissions, the German Federal Immission Control Act (BImSchG) considers light to be one of the types of immission that are likely to have harmful effects on the environment. In Slovenia, Italy and France, first laws have been adopted aiming at reducing light pollution.

The TA project will provide an overview of the state of knowledge with regard to the extent, current development trends and impacts of light pollution. On this basis, options for action shall be identified contributing to a reduction of light pollution and taking also into consideration the beneficial objectives of lighting. Thus, the debate on the pros and cons of artificial lighting at night shall be intensified and an evidence-based political support of ongoing developments with regard to lighting design and technology shall be enabled.

Project progress

In the context described above and in view of the objectives of the TA projects, two external expert analyses have been commissioned by the German Bundestag and another external expert analysis has been commissioned by the Helmholtz Centre for Environmental Research (UFZ) in Leipzig:

  • One of the expert analyses will take stock of the extent and growth of artificial lighting in German outdoor areas and work out current development trends with regard to lighting technology and design. On this basis, options for action to reduce light pollution shall be identified and described simultaneously taking into consideration the beneficial objectives of lighting.
  • Another expert analysis shall deal with the state of knowledge regarding the impacts of light pollution on different animal classes (e. g. birds, insects, fish etc.) and plants. It shall be shown in particular which correlations are considered to be sufficiently proven by corresponding scientific research, for which correlations there are some indications that, however, have to be examined more precisely and which further plausible aspects are still underrepresented in research as well.
  • Another expert analysis – on the one hand – shall give an overview of the state of knowledge regarding effects of artificial lighting at night that are relevant for human medicine, particularly with regard to the question of which of such effects (e. g. acute and chronobiological effects) artificial lighting at night actually has and which long-term health (and mental) effects are known or assumed in human medicine. On the other hand, the expert analysis shall point out the significance of unwanted light pollution for the above-mentioned effects of artificial lighting at night that are relevant for human medicine and which adjustments and innovations of lighting systems would be appropriate to reduce the effects of light pollution.