Consider for a moment: What is the most obvious form of pollution? Some may think of smog, a gray band of sooty haze hanging low in the urban sky. Others may envision patches of chemical and oil film floating on waterways. And of course there’s litter, lining the edges of city streets and highways.
However, there’s one form of pollution far more ubiquitous than any of these, readily visible from nearly every populated region of the industrialized world. It has degraded — and in many areas all but blotted out — some of the finest scenery this planet has to offer. It disrupts ecosystems and natural biological cycles. And it represents billions of dollars of lost energy costs annually. It’s light pollution, and for the vast majority of Americans, all you need to do to see it is step outside any night of the year and look up.
Goodbye, Milky Way
Simply put, light pollution is the unnatural glow in the sky caused by artificial lighting. Over the last century, it has become an increasingly familiar sight to urban and suburban residents — so familiar, in fact, that many appear to accept it as part of the natural landscape. Anyone who has attended a planetarium show will recall the “oohs and aahs” from the crowd (especially when school children are in attendance) when the lights go down and the projector first displays the full glory of the clear night sky. What may not be readily apparent at that moment is the fact that until very recently in human history, such a view of the constellations wasn’t some exotic display, it was instead one of the most common sights available to people everywhere.
In a pristine night sky, the average observer should be able to see around 2000 stars or so. Today, an urban dweller may be hard pressed to see more than a few dozen at most, while a suburbanite might be fortunate to see a few hundred. More delicate celestial structures, such as the faint glow of the Milky Way, are all but invisible in most populated areas. And whole generations have grown up probably thinking that the average cloud naturally glows at night.
Despite its obvious and widespread visible effects, light pollution does not to seem to rank very highly in the public conscious. This may be because most consider it a purely aesthetic problem, of interest primarily to a few stargazers and astronomers. However, the actual detrimental impact of light pollution runs far deeper.
The Endless Twilight
Increasingly, light pollution is coming under scrutiny due to its effects on the local ecology. There are a wide range of animal behaviors, such as mating, migration, and predation, on which a disruption in the natural day/night cycle may have a profound influence. Many diverse species of birds, bats, insects, amphibians, and even turtles have evolved critical biological functions that depend on natural darkness. Studies indicate that many of these creatures are being adversely affected by light pollution.
In addition, light pollution may also have a negative effect on humans. Research by the World Health Organization (WHO) and others show that regular periods of light and dark (also known as circadian rhythms) are essential for good health. For example, exposure to artificial light at night reduces the human body’s production of melatonin, a hormone that tells the body’s organs and systems that it is dark. Higher levels of melatonin slow the growth of breast cancer tumors in women and may similarly affect other cancers. This has prompted WHO’s International Agency for Research on Cancer to label “circadian disruption” as “probably carcinogenic to humans.”
Perhaps the most important driver in raising public awareness of light pollution is economic. As anyone who has ever flown a commercial airline flight at night can attest, a passenger can easily trace virtually the country’s entire infrastructure from the air, including glowing neighborhoods, bright ribbons of highways, and especially cities, shining brilliantly like dense Earth-bound star clusters. When one considers that every single photon of that represents wasted energy (since it does nothing to serve its intended purpose of illuminating the ground), it’s easy to comprehend the staggering cost involved.
According to the International Dark-Sky Association (IDA), some 22% of all energy generated in the U.S. is used for lighting, with 8% of that used for public outdoor lighting. The IDA also estimates that over $2 billion is wasted annually in the U.S. on energy consumed by stray light — a number that is likely to increase as energy costs continue to rise. Thus even overlooking the aesthetics, environmental, and health issues involved, light pollution should stand as an important issue based solely on economic factors.
Light pollution does offer some interesting commercialization possibilities. For example, the small telescope market has been estimated as around $100 million globally. Within this small but dedicated community, there is growing demand for telescopes that are both high performing and highly portable. As formerly rural areas lose their nights to suburban sprawl, amateur astronomers in these locations increasingly look to instruments that they can take with them on vacation to dark-sky sites. Further, there is a niche market for optical filters that preferentially block out wavelengths associated with artificial lighting and allow natural skylight to pass.
A far larger opportunity lies in outdoor lighting products that can reduce energy consumption. As noted above, billions of dollars are wasted annually on stray lighting. Lights that are designed to project all their illumination down towards their intended targets can be positioned as energy-saving products, since they are far more efficient than traditional lights. Some companies are also offering reflective shields that can be retrofitted onto existing lighting, directing more of their output towards the ground. Although the latter may represent an up-front investment, this cost can be potentially recouped through energy savings, as the more efficient lights can now produce the same level of illumination with fewer units.
To help promote products less conducive to light pollution, the IDA offers a Fixture Seal of Approval program. This is a third party rating system designed to assess the “sky friendliness” of lighting fixtures, based on photometric readings. Currently, some 100 manufacturers offer over 300 types of IDA approved fixtures.
Despite still being commonly perceived as lower on the list of environmental concerns, there is some evidence that light pollution as a public issue is gaining traction, with statewide light pollution control laws recently passed in Hawaii and New Hampshire, as well as national legislation in Italy. Such measures may indicate light pollution is an issue whose time may be coming, especially in terms of economics. If so, perhaps the time will return when more “oohs and aahs” are prompted by simply looking at the stars from one’s own back yard.
Dick McCarrick is an analyst with Foresight Science & Technology.