Passion of the people – 1.7.3

Aspects of light pollution

In a dark night sky, we can see approximately 3.000 stars. In a bright city, we can barely observe 100 stars nowadays. This has consequences that go way beyond sensual and cultural loss. While this page explains the key aspects of light pollution, it also gives recommendations for the right outdoor lighting.

Light pollution worsens air pollution.

Human lighting effects nighttime chemistry. During the day, pollution from motor traffic and factories pours into the air. At night, this is broken down by the nitrate radical NO3, a special form of nitrogen oxide that is destroyed by sunlight. Under a dark sky, NO3 purifies the atmosphere from other pollutants, a process called photolysis. With too much street and other outdoor lighting, the process is disturbed, thus leading to increased air pollution due to excessive outdoor lighting.

Light trespass disturbs people’s sleep and the human hormone balance.

Light smog permeates the whole planetary ecosystem.

Artificial light illuminates living spaces and metropolitan areas, but also—due to atmospheric reflection—otherwise dark areas. Light can dazzle. This has a negative impact on human health. Also, animals, plants and ecological systems are affected.

Illumination of the environment disturbs animals, plants and ecosystems.

Glare causes damage to the retina and increases the risk of accidents. [link to page 2.5]

The problem of bright, blue light

In a nutshell, the bluer and the brighter the light, the more harmful for humans, animals and plants alike. The atmosphere scatters blue light much more strongly than red light, which is why the cloudless daytime sky is blue. The phenomenon is called “Rayleigh scattering.” Short-wave or blue light sources are effective light polluters and should be avoided if possible. The reason is that this kind of light inhibits melatonin synthesis, the healthy production and flow of what we call “sleep hormone”, or melatonin. It has indeed a soporific effect on humans, but melatonin is a stimulant for nocturnal animals. Melatonin controls a variety of bodily functions and has antioxidant properties.

Recognizing colour temperatures, changing course

Colour temperature is the colour of light as perceived by the human eye. It is measured in kelvin. Pleasant indoor lighting has 2700 kelvin, while moonlight has a colour temperature of 4000 kelvin. The Kelvin scale, defined by a specific relationship between the pressure of a gas and the temperature, is an absolute temperature scale. According to the International Dark-Sky Association (IDA), high kelvin lighting (greater than 3000 kelvin) create a harsh glare, making it difficult to see clearly at night.[1] Choosing a light source of no more than 3000 kelvin therefore ensures that the amount of radiation under 490 nm is low and this limits the potential of detrimental health and environmental effects. Amber LED lamps (max. 2200 kelvin) and warm white LED lamps (max. 3000 kelvin) are recommended. They have low colour temperatures.

Deciding for the right light: red rather than blue

In general, organisms react differently to various spectral ranges. There is greater evidence, however, of detrimental effects from short-wave visible light, up to electromagnetic radiation with wavelengths of 490 nanometers (nm). Blue light has among the visible radiation the shortest wavelengths and therefore has particularly high energy. It is also known as HEV light, which is the abbreviation for “High Energy Visible.” Natural blue light generated by the sun has a significant influence on our life, acting as our inner clock and steering our circadian hormone cycle. It helps us get through the day feeling energized, alert and healthy. As the amount of blue light decreases towards evening, the body’s own process is reversed, making us tired. Hence the use of artificial blue, or short-wave, light disturbs human and ecosystem rhythms more than red light does.[2]

[1] https://www.darksky.org/

[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7065627/

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Passion of the people

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*Streetlight in Paris. Image by cocoparisienne – Pixabay*

*Street lighting in a German city. Image by gessinger – Pixabay*

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