Light pollution

Light pollution is increasing globally at an annual rate of 2–6%. The planning and implementation of new lighting systems often focus solely on efficiency, neglecting the protection of residential zones and ecosystems. Scientific studies show that intrusive lighting can have negative effects on organisms, ecosystems, and human health.

The rise of artificial light at night in urban areas disrupts biological, particularly circadian rhythms in humans. This disruption may contribute to poorer sleep quality and increased prevalence of civilisation-related diseases such as cancer, diabetes, and depression. Our department has long focused on research into circadian rhythms and the consequences of their disruption. The causes, risks, and potential consequences of light contamination were also addressed by the international project EU COST Action ES1204 LoNNe (Loss of the Night Network), in which we participated.

It is excessive, poorly directed, or unnecessary artificial light at night that wastes energy and money, while also:

• disrupting the natural day/night cycle,
• threatening nocturnal animal habitats and disturbing their biological rhythms,
• obscuring views of the starry night sky,
• disorienting insects and reducing biodiversity,
• negatively affecting human health (linked to insomnia, obesity, metabolic disorders, and cancer),
• potentially reducing safety due to glare,
• causing irritability and reducing the sense of privacy.

Recommendation 1: Lighting Direction

• Luminaires should never emit light above the horizontal plane.
• Upward-directed light serves no practical purpose and horizontally emitted light causes glare and reduces visibility.

Recommendation 2: Light Colour

• Avoid light with wavelengths below 500 nm (blue light) during the evening and night.
• Luminaires should have a correlated colour temperature of 3000 Kelvin or less (so-called “warm” light).

Recommendation 3: Lighting Intensity

• Existing standards should be reconsidered, as lower lighting intensity is often sufficient to ensure safety.

Full Statement (PDF) »

For Society

• Lighting should be carefully directed only at areas that need to be illuminated.
• The light source should not be visible from long distances (use shielding).
• No light should be emitted directly into the sky (avoid upward-facing floodlights).
• The overall brightness level should be reduced and applied uniformly.

For Individuals

• Avoid cool light (above 3000 K) in the evening and at night. Prefer sodium lamps or warm LED lights.
• When working on a computer or other devices, use a blue light filter (e.g., f.lux or built-in operating system features) to adjust screen emission according to the time of day.

A Practical Example from Austria

Explore the level of light pollution in your area using the interactive map.