If God or angels or extraterrestrials were monitoring us from above, the most profound change they would have witnessed on this planet since its creation is the pernicious illumination of our nights. Thousands of satellite images of the Earth taken over recent decades attest to the fact that the planet is growing dramatically brighter year by year.
So much of our use of light at night (LAN) is gratuitous. The International Dark Sky Association, an interdisciplinary organization concerned with global light pollution, offers compelling evidence that we are seriously overexposed to LAN, which is an unnecessary energy and economic burden, detrimental to wildlife, and a factor in global warming. A number of studies have linked excessive LAN to an increased risk for cancer. I believe that overexposure to light at night is the most critical overlooked environmental factor in our sleeplessness.
Readily witnessed in cities and our homes, excessive LAN may be the most obvious symptom of global warming. And also of personal warming. If global warming is the result of our collective mismanagement of energy, personal warming is its expression in our individual lives.
Our personal relationship with light is much like our relationship with food. Most of us are overfed but simultaneously undernourished. Likewise, we are overexposed to light, getting about one-third more exposure per day than our pre-industrial ancestors did. And most of this exposure is to poor quality artificial and poorly timed light what one of my patients called junk light. I believe that like junk food, junk light is an important factor in chronic inflammation our personal warming. Major sleep disorders are, in fact, associated with our personal inability to cool adequately at night.
