Light Pollution and Human Health The associated risks of fooling with Mother Nature Gene Fioretti, M.D.

“Many species (including humans) need darkness to survive and thrive.” American Medical Association Council on Science and Public Health (2012)

Humans are diurnal, that is, we evolved to be active during the day and to sleep at night. As such, we never developed the ability to see well in the dark. We have created an environment that corrects for our relative night blindness. Since the advent of electrical lighting around the turn of the 20 th century, humans have become increasingly exposed to bright and unnatural light at night.

Today, 99% of the population in the United States and Europe, and 62% of the world’s remaining population, are exposed to this “light pollution.” There is no denying that the invention of electrical lighting was a boon for developing industry and technology. However, the use of light at night continues to rapidly increase (by 6% per year) without thorough (or perhaps any) consideration of its biological implications.

Could Human Health really be affected by the lack of the night? Science teaches us that the earliest Homo habilis species evolved about 2.3 million years ago. Anatomically modern humans evolved about 200,000 years ago. The transition to behavioral modernity with the development of symbolic culture, language and specialized lithic (stone tool) technology happened around 50,000 years ago. We are indeed an ancient species. We have not physically or genetically changed for 30-50,000 years.

Mankind lived only by the day night cycle until the ability to control fire started somewhere around 400,000 years ago. The use of fire at night gave a warm glowing light. The use of indoor candles, torches and fireplaces have added length to the day for centuries. The introduction of the electric light in the late 19 th century heralded an explosion of night time light both indoors and outdoors. A new kind of light never experienced by mankind before.

Could Human Health really be affected by the lack of the night? In Order to know we need Science The development of the scientific method has allowed the rapid evolution of our knowledge of our planet and the universe. By constantly questioning our world, purposefully without regard to current dogma, our true understanding of things began its long history.

Should we have faith in science? Science is performed by human beings who are inherently vulnerable and potentially heavily influenced by their academic, scientific, cultural and political communities. Science requires funding. Funding may ultimately control those things that are investigated, and those things that are not. Science, to be of real value, requires fearless curiosity, honesty and transparency. Our knowledge is improved only with peer review, widespread dissemination and discussion, and finally refined direction of further study.

Beware…Science may be Complicated Misleading Misunderstood Misused to promote a single or limited point of view or philosophy.

Science and Trust So we have to trust the scientific community to present truthful and balanced information to us. The experts in a field are the filter that keep our knowledge as pure as it can be. It is our job to verify, then trust and act on the information.

Apply What We Have Learned Knowledge is useless unless applied. Application of what we have learned through science, despite its limitations, has led to the rapid advancement of our knowledge base. We have changed our world, but possibly not all for the betterment of mankind or the world.

Light at night may appear to be an innocuous environmental manipulation, which may be why it was overlooked as a significant disease risk factor for many years It is now evident that exposure to light at night has marked social, ecological, behavioral, and health consequences. Light under study

Light and Human Physiology The solar cycle of light and dark provide the essential basis for life on Earth. Adaptation to the solar cycle is deeply embedded in virtually all life forms and has resulted in it’s inherent circadian biological rhythm. Our internal systems have to be reset daily with the solar cycle to maintain proper temporal alignment with the environment.

Light and Human Physiology In humans and other mammals, this daily entrainment or circadian (from the Latin about the day) rhythm is achieved by non visual photoreceptors in the eye that transmit directly to the site of the circadian clock in the brain. Benefits of this system include precise regulation of rest, activity and adapting to seasonal changes in night length. Intensive study is ongoing in this area.

Impact of Light: Circadian Rhythm Light is not required to generate circadian rhythms. Totally blind individuals revert to an inherent endogenous non-24-hour clock (range hours) which is intermittently out of phase with the environment. This results in disruption of the sleep-wake cycle, alertness and performance patterns, the core body temperature rhythm, and melatonin and cortisol production (the “non-24-hr-sleep-wake disorder”).

Impact of Light on Human Physiology Another effect of light exposure at night is the immediate suppression of melatonin production. This would never occur in the natural environment. Electric light efficiently suppresses melatonin at intensities commonly experienced in the home at night.

Melatonin Chemical Structure

Melatonin What is melatonin? A hormone released by the Pineal gland at the base of the brain in response to a dark environment. Chief role is regulation of the wake-sleep cycle causing drowsiness and lowering body core temperature. Is intrinsically involved in cortisol and estrogen release. Derived from serotonin, a neurotransmitter involved in mood and appetite. Is an antioxidant which protects DNA from damage.

Research strongly suggests that melatonin has anti-cancer activities, especially in hormone sensitive cancers (breast and prostate). Excluding diabetes, totally blind women are half as likely to have breast cancer as sighted women. Melatonin suppression by light exposure at night (especially blue/white light), may actually be one of the reasons for the observed increased rates of breast cancer in night shift workers. More research is needed to prove cause and effect.

International Agency on Research on Cancer has classified shift work as “probably carcinogenic to humans” and some countries (e.g., Denmark) have classed breast cancer as an occupational health risk More recent studies have also begun to look at the association between exposure to light at night in general (outside the context of shift work) and the risk for developing certain types of cancer (breast and prostate).

Melatonin’s possible effects on cancer (a)A decrease in melatonin may increase estrogen/progesterone signaling, two known breast cancer promoters. (b) Melatonin may act directly on cancer and cancer-fighting cells that have melatonin receptors, reducing tumor growth. Melatonin can also affect tumor onset and development via its actions on oxidative stressors.

With the invention of electric lights, daylight hours have gradually been extended 4–7 hours depending on the season. As a result, overall melatonin production is suppressed in most people, not just shift workers. This marked decrease likely reduces the oncostatic (tumor suppressive) effects of melatonin, which has led researchers to hypothesize that light at night may contribute to the increased incidence of tumors in the general population.

To determine whether general lighting levels outside of a shift-working population also relate to breast cancer incidence, Kloog et al. obtained the average night-time illumination levels from 164 countries using the US Defense Meteorological Satellite Program, and concurrently evaluated breast cancer incidence from the GLOBOCAN 2002 database

A strong correlation was revealed between breast cancer rates and light at night. This is an important addition to the growing body of research on light at night and breast cancer because it demonstrates a population-level trend, whereas previous analyses examined only specific groups. Women living in the darkest communities may have prolonged durations of nightly melatonin, lowering their risk of breast cancer.

Clock Genes Certain genes called CLOCK genes regulate the transcription and translation of cellular feedback loops and are important regulators of cellular proliferation as well as “programmed cell death”. Rodent studies suggest that these CLOCK genes functions are regulated by our circadian clock, which if disrupted by light exposure could lead to cancer

Glare Disability glare result from bright points of light from poorly designed roadway lighting and car headlights. It is so intense we avert our eyes. Our vision is temporarily severely decreased. Older (over 60 y/o) drivers are especially vulnerable due to their aging eyes. Blue/white light has the biggest effect on our vision.

Some of the most expensive cars have the bluest brightest headlights

The Obesity Link “While conducting research on light at night and mood we noticed a strange trend; mice exposed to light at night were becoming fat.” Further study supported this observation. The eating habits of lab mice exposed to light became disrupted, eating more during the day when they are normally sleeping and inactive, thus gaining weight and becoming pre-diabetic. Circadian rhythm disruption has been shown to affect the CLOCK genes in mice and human adipose tissue. Research is ongoing. F1000 Med Rep v.3; 2011 PMC

Mood and Depression Fluctuations in daylight from season to season, abnormalities in the circadian clock, sleep disorders, and shift work are associated with depression in some subpopulations. Depression is often considered in the context of individuals who experience too little lighting (during the day), the so called Seasonal Affective Disorder. Rodent experimentation continues. Meanwhile light therapies are being used in clinical medicine.

Sleep Disorders According to the National Institute of Health(NIH), a shift in our internal clocks impairs our ability to sleep and wake at the appropriate times and leads to a decrease in cognitive and motor skills. Exposure to the artificially extended daytime of our lighted world can lead to desynchronization of our internal rhythm (clock).

Blue Light Exposure to blue light at night is particularly harmful. Unfortunately, most LEDs, increasingly used for outdoor lighting — as well as computer screens, TVs, and other electronic displays — create abundant blue light. To minimize harm from blue light, choose the right light bulb and download a color temperature app that adapts your electronic screen to the time of day – cool light during the day and warm light at night.

Keep it toward the Red

It is sometimes Easy to see the difference

The Kelvin scale and the tempera- ture of the fixture is depicted on the box.

The auto industry is not yet on board. Blue/White may be better for the driver, but not for oncoming traffic and overall safety

So, what have the medical experts at the American Medical Association said (2012)? 1. They support the need to reduce glare from vehicle headlamps and roadway lights, and the development of technologies at home and at work that minimize circadian disruption while maintaining visual efficiency.

The AMA said: 2. They warn that exposure to increased levels of light at night including various electronic media can disrupt sleep and exacerbate sleep disorders, especially in children and adolescence. They tell us that these effects can be minimized by using dim red lights in the nighttime bedroom environment.

The AMA said: 3. They support the need for further multidisciplinary research on the risks and benefits of occupational and environmental exposure to light at night.

The AMA has further Resolved To support light pollution reduction efforts and glare reduction at the national and state levels. That all future outdoor lighting be of energy efficient designs to reduce waste of energy and production of greenhouse gasses that result from this wasted energy To support efforts to ensure all future streetlights be of a fully shielded design or similar non-glare design to improve the safety of our roadways for all, but especially vision impaired and older drivers.

What can you do? Pick warm/red fixtures for the bedroom and use the minimum amount of light for safety purpose when up at night. Block out light trespassing in through your windows. Consider using warmer and less light overall during the evening and at night, and be sure you are not trespassing on your neighbor with your lighting.

Actively support the use of fully shielded and properly designed outdoor and roadway lighting in your community. Use only the light you need to get the job done. Use timers, dimmers and sensors to darken unoccupied areas. Shut off the lights whenever you can.

Finally Consider apps (f.lux, Twilight) that warm up your computer, phone or tablet’s visual output. Turn down the brightness of your indoor lights, as well as your computer, tablet and TV during the evening and at night. Download and use apps (eg. LuxMeter), to measure the lux in your home in the evening hours to help you adjust your lights and minimize your risk.