Human Health
Humans evolved to the rhythms of the natural light-dark cycle of day and night. The spread of artificial lighting means most of us no longer experience truly dark nights. Our bodies produce the hormone melatonin in response to circadian rhythm. Melatonin helps keep us healthy: It has antioxidant properties, induces sleep, boosts the immune system, lowers cholesterol, and helps the functioning of the thyroid, pancreas, ovaries, testes and adrenal glands. Night-time exposure to artificial light suppresses melatonin production. Research suggests that artificial light at night can negatively affect human health, increasing risks for obesity, depression, sleep disorders, diabetes, breast cancer and more.
An Israeli study used satellite photos to gauge the level of nighttime artificial light in 147 communities. The results showed a significant correlation between outdoor artificial light at night and breast cancer. Women living in neighborhoods where it was bright enough to read a book outside at midnight had a 73% higher risk of developing breast cancer than those residing in areas with the least outdoor artificial lighting.
The American Medical Association (AMA) officially supports light pollution reduction with a resolution approved on June 15, 2009:
RESOLVED
That our AMA advocate 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 use, and be it further
RESOLVED That our AMA develop and enact a policy that supports light pollution reduction efforts and glare reduction efforts at both the national and state levels; and be it further
RESOLVED That our AMA support that all future streetlights will 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.
Fear of increased crime is the most significant concern expressed by people when asked about reducing light pollution. It is commonly believed that nighttime lighting reduces crime, yet studies of crime conclude primarily that only our fear of crime is reduced. Although there is an overwhelming view that all-night lighting prevents crime, crime data do not show a strong relationship between lighting and crime rate.
Numerous investigations of the relationship of light and crime have been undertaken and are listed at http://amper.ped.muni.cz/light/crime/OLCpt2.htm and http://amper.ped.muni.cz/light/ctstarwchr/LiteLynx.htm#crime.
A test in West Sussex, UK showed crime went up in lit areas. In certain test areas, all-night lighting was installed; other areas were kept as control areas. West Sussex Police monitored the crime patterns for comparison with the previous year in both test and control areas and polled residents about their perceptions and the affects of the all-night lighting. Polling results confirmed people thought lighting prevents crime and most residents felt safer after the all-night lights were installed. Crime statistics, though, showed a 55% increase in crime in the test areas as compared to the control areas and to the county as a whole! West Sussex has subsequently decided against all-night lighting.
Energy Conservation
The United States of America wastes $130,000,000,000 a year on energy. Whether from inefficient light bulbs, unshielded lighting or vampire electronics, energy sources need improvement. So what small items can I procure to help save me money? High quality CCFL lightbulbs or appropriate LED lighting paired with the proper shielding, by directing the light downwards, allows a lower wattage bulb to emit the same amount of lumens as a bulb without the shielding. By directing the light downwards, consumers and businesses alike, can begin to waste less energy and eradicate light pollution.
Ecology
Plants and animal depend on Earth’s daily light and dark cycle to govern life-substaning behaviours. Research shows that artificial light at night has negative and even deadly effects on many species. The dark side of light at night is a great article on the effects of light pollution has on the ecology.
Astronomy
Light pollution negatively affects one of our greatest natural laboratories, the night skies. Light pollution sets the sky aglow, in much the same way that the sun sets the sky aglow during the day. The increase in sky glow caused by cities is enough to make it difficult to see dim objects in the sky. When astronomers try to take a picture of a very dim object, sometimes the glow from the sky is too bright to ever see the object clearly.
A second way city lights interfere with astronomy is much more insidious. Often, astronomers want to take the spectra of an object, splitting the light from the telescope into its component colours. When you take a spectrum of fluorescing objects like galaxies, you see that the spectrum is not smooth, but made up of a number of lines. Each line is a unique indicator of the presence of a certain chemical. By studying the strengths of these lines, astronomers can deduce the chemical composition and temperatures of the objects they observe. By noting the redshift of the lines (how far to the red side of the spectrum they are shifted), astronomers can determine how fast the object is moving. Spectroscopy is probably the most valuable tool in the astronomers’ toolbox. Unfortunately, city lights play havoc with spectrographs.