Table of Contents

Light Pollution

In the US, over 3 billion dollars of energy every year is lost to inefficient public lighting coverage. Not only is this loss devastating to economies, over 80% of the population live in overlit areas that disturb your natural circadian rhythm, interfere with migratory patterns, and cloak our window into the cosmos. 

Key Terms:

ALAN - Artificial Lighting at Night

What is it?:

Light becomes a pollutant when it causes glare, inhibits the view of stars, is not used in the area, and when it is unwanted in an area. [7]

Effects can come from direct exposure or from sky glow [4]

Negative Effects:

The light pollution from big cities have a wide spread effect on surrounding areas. [2]

Plants use light cues to perceive time and as a source of circadian rhythm synchronization. These light cues were relatively consistent over the evolution of the species, and the introduction of ALANs has been too abrupt for them to adapt quickly. In a study on the effects of ALANs on crop harvests it was shown that plant community biomass, diversity, and evenness all decreased when exposed to ALANs and changes in the expression of plant traits show additional alarming effects. [4] These effects on plants can have a domino effect on other aspects of a healthy ecosystem and population (e.g. Agriculture, Food Chains, etc.).

Evidence suggests that exposure to light at night can contribute to mental illness. For example, mood, cognition, and metabolic processes can be disrupted. Disruption in the natural circadian rhythm can increase the risk of developing dementia or Alzheimer’s disease. “Sundown syndrome” is an example of light’s effect on mental well-being. In dementia patients, symptoms can worsen at night or in the evenings. It has been shown that therapeutic lighting or a decrease in ALAN alleviates symptoms and boosts recovery. In a study on the effect of ALAN on patients with dementia, it was demonstrated that increased exposure contributed to worsening psychotic symptoms. [12]

Severity of the Problem:

From 2011 to 2022, the number of visible stars decreased due to population growth, new technologies, and expanding cities/towns. [1] ALAN increases globally at rates of 1.6 - 9.6% per year. Artificial lighting affects about 25% of Earth’s land surface and 88% of Europe and is considered a significant environmental pollutant. [2]

Short wavelengths of light scatter better in the atmosphere and increase sky glow. [1]

There is no reliable way for us to measure sky glow due to the limited sensitivity of existing telescopes and satellite imagery. Additionally, existing citizen science data is extremely biased to Europe and North America, so it is difficult to quantify skyglow in the other areas without using unreliable satellite measures. [1]

Although municipal lighting can contribute greatly to the light pollution in an area, according to a novel German study led by Dr. Christopher Kyba, other sources also add to the issue. In some areas, streetlights made up as little as 13% of the ALAN sources. Other sources can include residential lit windows, commercial windows, floodlights, and light-up signs. [2] Light pollution can not be eliminated by policy changes alone.

Different times of night can display different levels of light pollution due to changes in type, color, and direction throughout the night [2]

The Bortle Scale

• Johnstown has a 19.08 SQM [5]

• Johnstown has a 39.2% LP Index [5]

Ways to Fight:

• Dimming some lights, covering upward facing lights, using red spectra when possible [7]

• Warm colors -

Efficient LEDs are often brighter and whiter, and contribute significantly to light pollution when used in public street lighting. [7]  This can draw a parallel to the Jevons Paradox; as LEDs became cheaper and more “efficient,” demand and usage increased. The availability and low cost decreased awareness for over usage of these lights. 

White LEDs emit at wavelengths from around 450 nm - 460 nm (blue light). This blue light then creates the effect of white light to the human eye through phosphor conversion in the bulb. [10]

Image Credit: CIBSE Journal, Iain Macrae, December 2022

• Light only when needed - 

• Keeping lights dim - 

• Etc. 

Policies:

LUNA certification: “LUNA products can help capture energy savings by using the right type and amount of light, and only where and when it is needed.” However, for this mitigation to be successful, the product must be used responsibly (Where and when light is needed).  LUNA Authorities are hopeful that in version 2.0, they can include requirements about the spectral properties (color spectrum) measured by correlated color temperature (CCT). [8]

Policy Enforcement - 

 The “red lines” approach. In this approach, regions are limited by how much light pollution they are allowed to emit. Using various indicators, the local enforcement would monitor these indicators and can enact restrictions if any areas exceed those emissions. This is especially useful in places that attract tourism for their dark skies or natural beauty. [9]

Common Concerns:

• Safety - 

• Money - 

Intrinsic Value:

Art that has been made about the night sky and stars (e.g., Vincent van Gogh's “Starry Night”) [3]

Dark Sky Sanctuaries and Inspiration:

State Administrative Code Rule 62B-33 in Florida protects fragile beach environments by approving and overseeing light fixtures within a certain range of beaches or in areas that may harm wildlife. Additionally, buildings near the coast must use amber colored lighting. “Keep it low, Keep it long [wavelength], Keep it shielded” is the Florida Fish and Wildlife beach lighting catchphrase. Satellite imaging has shown that these policies have caused the light pollution to decrease and the turtle population on the beaches to increase. Seasonal shifts from white light during nesting season have also made a positive impact [7]