Light Pollution: Human Health Impact And Solutions

Light pollution, caused by the excessive or inappropriate use of outdoor artificial light, is having a detrimental impact on human health. The proliferation of artificial light at night means that most people no longer experience truly dark nights, and this is causing a range of health issues. Research has shown that exposure to artificial light at night negatively affects human health, including an increased risk of obesity, depression, sleep disorders, diabetes, breast cancer, and more. This is because artificial light disrupts the natural circadian rhythm, or body clock, which is linked to the day and night cycle and helps cue the body to get hungry or tired and to release certain hormones.

Circadian rhythm disruption

Circadian rhythm, often referred to as our "body clock", is a 24-hour sleep-wake pattern that is governed by the natural day/night cycle. This cycle is largely influenced by photoreceptors in the eye that are more sensitive to blue wavelengths of light. Circadian rhythm helps cue our body to get hungry or tired and to release certain hormones.

Artificial light at night can disrupt this cycle. Research has shown that exposure to artificial light at night is associated with an increased risk of sleep disorders, obesity, depression, diabetes, breast cancer, and more.

According to the American Medical Association, white LED lamps have five times the impact on circadian sleep rhythms than conventional street lamps. Brighter residential nighttime lighting is associated with reduced sleep times, dissatisfaction with sleep quality, excessive sleepiness, impaired daytime functioning, and obesity.

To maintain a healthy circadian cycle, it is important to experience outdoor lighting during the day and minimize the amount of light entering our eyes at night.

Today's best practice for nighttime lighting is to minimize exposure to light, especially blue light. When at home at night, it is recommended to use dimmers and lower-CCT light bulbs, and utilize color temperature apps that adapt electronic screens to the time of day – "cool" appearing light during the day and "warm" appearing light at night.

By taking steps to reduce our exposure to artificial light at night and prioritize natural light during the day, we can help maintain a healthy circadian rhythm and mitigate the negative health effects of light pollution.

Sleep deprivation

Light pollution can have a significant impact on human health, particularly when it comes to sleep deprivation. As our exposure to artificial light at night increases, so too does its negative influence on our sleep-wake cycles, or circadian rhythms. These rhythms are governed by our body's biological clock, which is largely influenced by photoreceptors in the eye that are sensitive to blue wavelengths of light.

The issue of light pollution is particularly pertinent given the proliferation of artificial light sources in modern times. The bright glow of city lights, illuminated buildings, and technology such as smartphones and laptops, all contribute to this issue. As a result, many people no longer experience truly dark nights, which can have a detrimental effect on their health.

The human body's circadian rhythm is regulated by the suprachiasmatic nucleus (SCN), a part of the hypothalamus in the brain. The SCN is highly sensitive to light exposure, as light provides an external cue for internal clock regulation. When exposed to artificial light, the SCN initiates a signaling pathway that leads to a reduction in melatonin production. Melatonin is a hormone responsible for regulating our sleep-wake cycles, inducing sleep, boosting the immune system, and aiding the functioning of various glands.

Research has found that exposure to artificial light at night is associated with an increased risk of sleep disorders. A study of over 50,000 older adults in South Korea revealed that those in brightly lit areas, as judged by satellite data, were more likely to use sleep medication and took higher doses than those in less illuminated areas. This confirms the link between light pollution and sleep deprivation, with the study authors recommending that public officials address this issue.

Furthermore, the disruption of healthy sleeping patterns due to light pollution has been linked to an increased risk of certain cancers. Studies have found an association between working night shifts and an elevated risk of breast cancer, with constant exposure to artificial light potentially accelerating tumor growth. Additionally, sleep deprivation can interfere with cancer suppression genes, increasing the risk of breast, prostate, gastric, and lung cancers. Thus, the impact of light pollution on sleep deprivation and subsequent health consequences is a growing area of concern.

Blue light and screen time

Blue light, emitted by electronic devices such as smartphones and computers, as well as light-emitting diodes (LEDs) used in industrial and city lighting, has been shown to negatively impact human health. The issue is particularly pressing given the prevalence of these devices in modern life.

The human body has a natural circadian rhythm, a "body clock" that is influenced by the day and night cycle. This rhythm is largely governed by photoreceptors in the eye that are sensitive to blue light. When exposed to blue light, the body suppresses the production of melatonin, a hormone that is crucial for maintaining healthy bodily functions. Melatonin not only induces sleep but also boosts the immune system, lowers cholesterol, and helps the functioning of the thyroid, ovaries, pancreas, testes, and adrenal glands.

The impact of blue light on melatonin suppression has been linked to various health issues. Firstly, it can lead to sleep disorders, including reduced sleep times, dissatisfaction with sleep quality, excessive sleepiness, and impaired daytime functioning. Additionally, blue light exposure has been associated with an increased risk of obesity, depression, diabetes, and breast cancer.

To mitigate the negative effects of blue light, individuals can take several steps. Adjusting the settings on smartphones and computers to emit a lower light intensity during the night can be beneficial. Utilizing color temperature apps that adapt screen colors to the time of day is also recommended, opting for "cool" appearing light during the day and "warm" appearing light at night. Furthermore, individuals should consider reducing screen time before bed, as the high color temperature of light from electronic devices can confuse the brain into thinking it is still daytime, disrupting the natural sleep cycle.

While blue light has its drawbacks, it is important to note that exposure to bright light during the day is beneficial for maintaining a healthy circadian rhythm. Natural daylight provides the ideal lighting conditions to support this rhythm, but when access to natural light is limited, individuals can opt for "cool" or bluer light sources to mimic the daytime lighting environment.

Melatonin deficiency

Melatonin is a hormone that is naturally made by the body and is essential for sleep. It is closely tied to light; when it is dark, the pineal gland in the brain initiates melatonin production, but light exposure slows or halts this process.

The adverse health effects of melatonin suppression are becoming increasingly evident. Melatonin regulates many bodily functions, including sleep, metabolism, endocrine and epigenetic abnormalities, and immune system functioning. It also has antioxidant properties, lowers cholesterol, and helps the functioning of the thyroid, pancreas, ovaries, testes, and adrenal glands.

Research has found a link between melatonin suppression and an increased risk of certain types of cancer, particularly breast cancer. Studies have shown that exposure to artificial light at night is associated with a higher risk of developing breast cancer. Melatonin deficiency may also increase the risk of other types of cancer, although more research is needed to confirm this.

To reduce the risk of melatonin deficiency, it is important to minimize exposure to light at night, especially blue light. Using dimmers, lower-CCT light bulbs, and colour temperature apps that adapt electronic screen colours to the time of day can help reduce blue light exposure.

Obesity and diabetes

Light pollution has been linked to obesity and diabetes, with research suggesting that exposure to artificial light at night can negatively impact human health.

Circadian Rhythm and Melatonin

Like most life on Earth, humans adhere to a circadian rhythm — a sleep-wake pattern that is governed by the natural day/night cycle. This cycle is largely influenced by photoreceptors in the eye that are more sensitive to blue wavelengths of light. It is important for humans to experience outdoor lighting during the day and minimise the amount of light entering their eyes at night to maintain a good circadian cycle. Artificial light at night can, unfortunately, disrupt that cycle.

Impact on Melatonin

Night-time exposure to artificial light also suppresses melatonin production, which is needed to keep us healthy. Melatonin has antioxidant properties, induces sleep, boosts the immune system, lowers cholesterol, and helps the functioning of the thyroid, pancreas, ovaries, testes, and adrenal glands.

Impact on Obesity and Diabetes

A study of nearly 100,000 Chinese adults found that people who lived in areas with high light pollution at night were about 28% more likely to develop diabetes than people who lived in the least polluted areas. Another study of 43,000 women found that those who slept with a television or light on were more likely to gain weight and develop obesity.

Environmental Factors

Endocrine-disrupting chemicals in the environment have been linked to obesity and diabetes. Bisphenol A (BPA), for example, has been implicated in the development of obesity due to disrupted patterns of hormone regulation and adipocyte differentiation. BPA has long been known to leach from plastics and to have deleterious health effects at low levels.

The "built environment" is another factor influencing the development of obesity and diabetes. The "built environment" refers to the patterns of human behaviour within the physical world, encompassing urban design, land use, and transportation systems. Research has confirmed dose-response associations between features of the built environment and the prevalence of overweight/obesity. For example, in Portland, Oregon, a 10% increase in land-use mix has been associated with a 25% reduction in the prevalence of overweight/obesity.

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