Bright Side of the Night – 2.5.1

Physiological Dimensions of Light Pollution

Consequences for Human Health

Artificial light is defined as any ambient or external light source that is not derived from natural sources. In the scientific publication, “Light Pollution: a systematic review about the impacts of artificial light on human health”, the authors demonstrate that the illumination of the night sky by artificial light has a significant impact on a range of health conditions, including obesity, diabetes, depression, and heart attack. Apparently, the exposure to as little as 3 lx of artificial light before bedtime is sufficient to increase human blood pressure overnight. The researchers conclude that the increase in exposure to artificial light triggers mainly sleep and mood disorders, with light from electronic devices and artificial night the main source of pollution. Typical consequences of artificial light exposure include disturbances of the circadian- or biological – rhythm due to alterations in the levels of melatonin and cortisol and specific metabolites. These physiological changes can in turn lead to depression as well as to alterations in spermatogenesis, ocular structures, thermoregulation, and other cardiovascular conditions.

Too Much Light, Too Little Sleep

Excessive artificial light at night is not only irritating – it directly affects the cycle and production of the sleep hormone melatonin and thus the circadian rhythm. This affects sleep, quiet, and rest, with far-reaching consequences for human health. This is because artificial light at night in the short wavelength range below 490 nm can suppress the release of melatonin for more than an hour and a half. Short-wave radiation from smartphones, tablets, e-readers, and computer screens is specifically detrimental. Night mode and blue light filter software provide a remedy.

Too Much Light Can Harm You?

As we age, it is normal for the cornea, lens, and vitreous body of the eye to become cloudy, causing more short-wavelength light to be scattered in the lens and therefore more glare. However, excessive or inappropriate exposure to artificial light can result in a premature loss of visual acuity. The constant exposure of the human eye to low-intensity short-wavelength light (e.g. computer screen) for 12 to 48 hours has been linked to accelerated degeneration in eyesight, retinal damage, and age-related macular degeneration. Permanent damage to the retina can also occur within a few minutes if the eye is intensely dazzled by high levels of illuminance and short-wave radiation, e.g. from the sun or a projector.

The Science of Secure Street Illumination

More light does not always mean better vision. Artificial light can also introduce traffic risks, such as dazzle and distraction. In the dark, visual acuity decreases, colours are less distinguishable, and sensitivity to glare increases. The human eye involuntarily focuses on the strongest light source and adapts to it. The time available for navigation and hazard detection is reduced. The eyes are strained and fatigue sets in. Advertising installations such as LED screens, flashing warning lights, streetlamps, and oncoming headlights can all irritate and distract the driver, with potentially serious consequences.

Driving Blind Through Glare

Strong light-dark contrasts and high luminance levels cause glare. While the human eye has an excellent ability to adapt to different levels of brightness, full adaptation from light to dark takes up to 30 minutes. In the case of a sudden change from light to dark, normal visual perception is not available for the first few seconds. You are virtually blind. Therefore, municipalities, road traffic regulators, and procurement offices are called to inquire carefully about possible glare from streetlamps. There are a number of rules and regulations governing road traffic, but they can vary from country to country. They set limit values and specify criteria to ensure that road users do not experience significant problems from the road infrastructure, including visual information such as roadside signs. The focus shall be on reduced light intensities, low light-dark contrasts, and warm white color temperatures.

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*City lights. Image by Pexels – Pixabay*.

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Images

Numerous images of the night sky can be downloaded on Pixabay.