The tension between nighttime lighting and public safety

I was disappointed but not surprised to see that the University of Minnesota plans to install brighter lights in response to the recent crime wave on the Twin Cities campus ("U installs new safety measures for campus," Jan. 22).

Contrary to accepted wisdom, brighter lights do not automatically make us safer. In fact, overusing light at night can actually reduce security, even as it incurs numerous other costs. Before the university spends thousands of tax dollars "improving" the lighting on campus, I would urge officials to consider their choices carefully.

When the goal is to improve our safety at night, installing brighter lights is rarely the answer. Because some light at night can undeniably improve our safety, we too often assume that ever-increasing amounts of light will make us evermore secure. Unfortunately, there is almost no research to support this belief. What research we do have on the relationship of light at night and crime is equivocal at best, and as often suggests that reducing lighting levels — rather than increasing them — improves safety most.

It is far more important that we light thoughtfully and intelligently than simply decide, as one London official told me, "We're just going to have loads of it!"

While researching a book I wrote on the importance of darkness, I heard experts in lighting and security explain that lights that are too bright can reduce our safety by 1) casting shadows where criminals can hide, choose their victims and escape; 2) creating blinding glare that makes it harder to see, and 3) creating an illusion of safety that tempts us to act less cautiously than we otherwise might.

Our ever-increasing use of light at night comes with tremendous costs. Recent estimates from the International Dark-Sky Association are that worldwide we waste more than $110 billion on light at night and produce an unnecessary 750 million tons of CO2.

As for human health, scientists are finding that artificial light at night is disrupting our sleep, confusing our circadian rhythms and impeding the production of the hormone melatonin — a hormone produced only in the dark. The lack of melatonin in our blood has been linked to an increased risk of breast and prostate cancer, and the World Health Organization now considers working the night shift a probable carcinogen, in the same category as breathing diesel fumes.

Additionally, in a world where 60 percent of invertebrate species and 30 percent of vertebrates are nocturnal, and countless other species are most active at dawn and dusk, all this wasted light at night is taking a tremendous environmental toll — one we are only beginning to understand.

Finally, we have robbed ourselves and our children of the wondrous night sky that has inspired art, science, religion and philosophy since human history began.

The good news is that controlling these costs from light pollution goes hand in hand with lighting for safety at night. That's because we can make tremendous strides in controlling light pollution by using shielded fixtures that allow light to shine only downward where we want it, rather than into the sky, into our eyes or into our homes (a situation so common that astronomers have a name for it: light trespass). These same shielded fixtures are also the best for safety because they do not cast shadows or glare, and they allow us to see clearly.

If we are serious about improving safety and security at night — whether on campus or in our cities, our communities, or our neighborhoods — we will begin to use our light more intelligently, responsibly and thoughtfully. Among other things, this means refraining from rushing to install brighter lights in response to a crime wave.

Light at night is a good thing, but too much light is not.

Paul Bogard, of Minneapolis, is the author of "The End of Night."