A new LED streetlight with a “shield” installed on Harvey Street. (Photo: Charles Teague)

Almost 5,000 streetlights in Cambridge will be replaced with LED versions by the end of this month. The good news is the dramatic energy savings. The bad news is complaints by residents that the new streetlights are too bright and too “blue” compared with the old, “warm” high pressure sodium lights. It is really bad news for my friend’s teenage son, who hasn’t got a decent night’s sleep since the replacement.

More good news, bad news: The city will install shields on offending streetlights, and all new streetlights will be dimmed once the control system is working, but a 2012 Harvard Medical School newsletter warns that “Light at night is bad for your health, and exposure to blue light emitted by electronics and energy-efficient lightbulbs may be especially so.” In other words, the closer to your bedtime and the “bluer” the light, the more you’ll want to consider unwanted light coming into your home from the city or office building next door a health hazard. Just as we did not know or appreciate the serious public health issues with secondhand smoke, we are now learning of very similar issues with secondhand light.

But the really bad news is that the city wants to change the law prohibiting intrusive light from public and private sources to make itself exempt, reduce other existing protections, legalize currently illegal lights and to specifically allow those “bluer” lights. The city will also soon specify replacements for park lights and decorative streetlights. Residents need to act now because we must choose wisely lights that will last for decades instead of years.

There are three types of new streetlights with 40, 80, and 120 LEDs that will be initially dimmed to 70 percent, then down to 35 percent later in the night. The LEDs are rated at a 4,000 Kelvin color temperature, the same as a Phillips “Cool White” fluorescent, which is “cooler” (having more “blue” light) than a 3,000-K “Soft White” florescent bulb. By way of comparison, the old HPS streetlights are 2,100 K, which is much “warmer” than your conventional 2,800-K incandescent “Soft White” bulb. LED streetlights are now available at 3,000 K.

Police like the “bluer” light because it helps witnesses accurately report colors, such as whether they saw a blue or green car at a crime scene. Seattle’s Crosscut.com, in writing about the LED conversion controversy, sums it up: “Politicians like any excuse to proclaim that they’ve made the streets lighter, brighter and safer. Street lighting is like long, determinate prison sentences: More is always presumed to be better, and no politician ever lost an election calling for it.”

Health concerns

There are reasons to worry about leaks from this brighter, bluer lighting, though. Researchers are finding increasingly that out-of-phase circadian rhythm is a health hazard. “Maintaining synchronized circadian rhythms is important to health and well-being,” says Dieter Kunz, director of the Sleep Research and Clinical Chronobiology Research Group at Charité–Universitätsmedizin Berlin. “A growing body of evidence suggests that a desynchronization of circadian rhythms may play a role in various tumoral diseases, diabetes, obesity and depression.”

Shift workers are considered most at risk, but even dim light can interfere with a person’s circadian rhythm and melatonin secretion. A mere eight lux – a level of brightness exceeded by most table lamps and about twice that of a night light – has an effect, notes Stephen Lockley, a Harvard sleep researcher. Light at night is part of the reason so many people don’t get enough sleep, Lockley says, and researchers have linked short sleep to increased risk for depression, as well as diabetes and cardiovascular problems.

Compare for yourself

Look at the color of lights (Do you want your neighbors, corporate or otherwise, to be allowed to use lights that color?), the brightness (Do you need more, or can you do with less?) and where the light spills onto homes (See if there are distinct shadows of trees on facades). Lexington Avenue off Fresh Pond has 40 LED lights dimmed to 70 percent right now but do not have the “late night” dimming to 35 percent at this time. Berkeley Street near Harvard Square is a great viewing opportunity; it has a mix of soon-to-be-dimmed 40 LED lights and old HPS lights. Around the corner on Craigie Street are 80 LED lights.

Certainly replacing the streetlights has many benefits: saving a half-million dollars a year and reducing energy use by 75 percent, bulbs lasting decades instead of years, reducing light reflected up into the night sky and reducing light shining into people’s windows.

But we should take great care when choosing the color temperature of our city’s next LED purchase for our decorative streetlights and parks. We also should be certain to “first do no harm” when changing our law that prevents direct light from anyone from shining onto adjacent property. We must make sure our law does not go from being difficult to enforce to impossible. Our city should not only not be exempt from the law – it should lead by example in being a good lighting neighbor.

What can you do?

Send an email here to subscribe to an email discussion group that includes all the members of the City Manager’s Lighting Ordinance Task Force. Then educate yourself by reading the current ordinance (sections 7.20, 7.15B, 6.41, 6.46, 6.93),  the draft ordinance and city’s very good streetlight explanation. Read about health issues in the Harvard newsletter and National Institute of Health articles on blue light and light pollution. Watch the videos of a Massachusetts Institute of Technology professor describing light pollution from the East Cambridge Courthouse redevelopment, a Harvard Medical School professor describing the public health issues and the City Council voting down my improvements to our current light law that tried to make enforcement easier and to cover all neighborhoods.

Finally, show up at the “final” task force meeting, scheduled for 4 to 6 p.m. Aug. 20 on the fourth floor of City Hall Annex, 344 Broadway. Public comment is scheduled for the end.

Charles Teague is a member of the city’s Lighting Ordinance Task Force.

This post was updated Aug. 10, 2014, to make the graphics and text conform with scientific nomenclature and the timeline of city changes to streetlight.