In addition to hurting our environment and the lives of animals, many do not realize that light pollution also affects us. There have been studies proving that light pollution has negative effects on our own human health. Our bodies possess a physiological system called circadian rhythm, which is our biological clock based on a day-night cycle. This process stimulates brain wave patterns, hormone production of melatonin, cell regulation, and other biological activities. If your circadian rhythm is disrupted, it can result in health issues such as obesity, sleeping disorders, diabetes, depression, cancer, cardiovascular disease and more (Filmer).
The effects of light pollution can go beyond just sleep disorders. Light pollution suppresses the production of melatonin, which is a hormone produced in the dark hours of circadian rhythm. Melatonin is what helps keep our bodies healthy. It contains antioxidant properties, induces sleep, boosts our immune system, and lowers cholesterol; while assisting with the functions of the thyroid, pancreas, ovaries, testes and adrenal glands. Melatonin is related to cancer in several pathways, including effects on estrogen-receptor positive human breast cancer cells. Some studies have found a connection between exposure to artificial light at night and hormone-dependent cancers (Hill et al).
Many researchers believe that light pollution may be “carcinogenic” for humans. A study was conducted in 11 different Spanish regions and had compared those who were exposed to indoor versus outdoor exposure. The participants ranged in age from 20 to 85 from the years 2008 to 2013. Indoor exposure to light was determined by personal questionnaires, and outdoor exposure was evaluated based on nocturnal images taken by astronauts from the International Space Station. The study concluded that “both prostate and breast cancer were associated with high estimated exposure to outdoor artificial light at night in the blue-enriched light spectrum.” Compared to their control group, the participants exposed to higher levels of blue light had 1.5-times higher risk of developing breast cancer and 2-times higher risk of developing prostate cancer (Ariadna Garcia-Saenz et al).
Light pollution can, obviously, result in sleep disorders. Circadian disruptions can lead to a number of sleep disorders, including shift-work sleep disorder (SWSD) and delayed sleep-phase syndrome (DSPS). SWSD affects people who rotate shifts or work at night, and DSPS refers to people who fall asleep very late at night and have difficulty waking up in time for work, school, or other obligations. Artificial light in the bedroom- including blue light from cell phones, televisions, and laptops- is extremely harmful. It is recommended that these devices be taken out of the bedroom for the dark environment needed for sleep (Chepesiuk).
In a study published by Pediatric Research in August of 2006, they exposed newborn mice to constant artificial light for several weeks, in order to research the possible effects of artificial light exposure to developing circadian rhythms of premature babies in neonatal intensive care units. The exposed mice were unable to maintain a coherent circadian cycle at the age of 3 weeks, and mice exposed for an addition 4 weeks were unable to establish a regular activity cycle. The researchers concluded from this study that an excessive amount of artificial light exposure early in life might contribute to an increased risk of depression and other mood disorders in humans. The lead researcher Douglas McMahon stated that this data indicates that human infants benefit from the synchronizing effect of a normal light and dark cycle.
Glare- one of the three main types of light pollution, alongside light trespass and skyglow- is a public health hazard. Glare from poorly shielded outdoor lighting is harmful to our health because it decreases vision and can cause loss of contrast or sometimes blind you temporarily. This is especially a hazard at night and for aging eyes, which could potentially lead to unsafe driving conditions (Association of Universities for Research in Astronomy).
Unfortunately, the true causes of light pollution remain unknown and the research is not going at the pace that it should be. According to Susan Golden, a professor at the Center for Research on Biological Clocks of Texas A&M University, she says, “Light pollution is still way down the list of important environmental issues needing study. That’s why it’s so hard to get funds to research the issue.”
Light Pollution: How Does it Impact People?
I knew exposure UV light or any type of high-frequency wave could cause cancer, but I never thought that something on the spectrum of visible light could be as dangerous. It’s kind of scary because those kinds of lights are very common in schools, offices, or other public places.
I had heard of the circadian rhythm but had no clue as to how much it affected the average joe. The studies done on people and their interaction with light compared to the presence of cancers are super interesting and I have made a note in my head to try and find some more material on that. I would have never guessed that the two could be related. As for the other determinantal effects on humans, it makes me even happier that it is getting warmer out so that I can go back outside soon and get away from the inside light!
This is both very interesting and scary. Circadian rhythms are definitely interesting to read about, but it’s scary to think that light can cause sleep disorders and cancer.
Also, it’s so cool that images taken by the International Space Station are used for light pollution research!