More songbirds or more browntail moths?

Bath is replacing old streetlights with LEDs, as communities have been doing for a decade. Over that time, lighting technology has advanced rapidly. Our understanding of harmful effects from bluer LEDs also increased. In January, a 12-year study in the journal Science demonstrated that light pollution is increasing five times faster than previous estimates, doubling every eight years.

Bath plans to install 2700K (degrees Kelvin) streetlights. But with improved technology and efficiency, warmer 2200K LEDs cut harmful blue light emissions by 50% compared to 2700K, reducing environmental impact on birds and other wildlife. Our group, Street Lighting for Bath’s Future, spoke at the May City Council Meeting, along with others favoring vintage lighting better suited to Bath’s downtown and historic homes.

We met with City Manager Meyers later and asked, “Why not choose the best option?” He said that 2700K was a compromise between reduced safety with 2200K, and increased light pollution with “brighter” 4000K LEDs. This of course is a misunderstanding that all lighting engineers are familiar with: Safe lighting levels are based on lumens, not the light color.

Warmer lighting in fact increases the margin of safety for our aging population, since we progressively lose visibility under bluer lighting as we age. This is covered in Section 2.3.5 of the IES Standards that guide all street lighting practice in the US.

Mark Carter of RealTerm Energy, leading the LED streetlight project, provided this assurance:

“RealTerm Energy has never said 2200K was unsafe nor outside of IES Standards, in fact we have informed the council of our nearby Harpswell where we have a 2200K town-wide deployment.”

We asked city councilors to take a vote on choosing warmer lighting. We should not spend $330,000 for yesterday’s technology based on a misunderstanding.

But at this point, Bath’s elected representatives may not get a chance to vote. On procedural grounds, a minority on the Council is blocking a vote about which lights residents will see outside their homes. And will continue to see when they drive or walk in the city every night for the next 20 years.

Russell Clark,
Bath