Chicago, the Night Should Not Look Like the Day

Chicago has been replacing its high-pressure sodium lamps with 3000K LEDs. They are finding many objections to the level of glare and brightness, but the Chicago Tribune editorial board came out with a ringing endorsement of full-spectrum white light, and celebrating the loss of yellow and orange hue of high-pressure sodium. This is my response.

Chicago should not be celebrating whiter nighttime lighting.  As a researcher in the field, the better choice for human health and to reduce wildlife impacts is to use warmer (yellower) light that has more in common with the old sodium vapor than the new bright white LEDs.  White light, which contains blue in it, tells the body that it is daytime and interferes with the essential repair and recovery processes that take place during the night. 

According to Department of Energy research, the new lights may well reduce light pollution at a distance, but only if they are set to less than half of the light output of the old sodium vapor lights and are installed so that absolutely no light escapes upwards.  But this does not help those people and wildlife below the lights, as a recent study from NEIU showed the pervasive impact of light pollution on the Chicago’s wildlife, documenting significant impacts across the region’s impressive open space network and neighborhoods. Spanish researchers found greater incidence of cancer in areas with white LEDs compared with sodium vapor lighting areas after controlling for all other factors.

Chicago leaders did the right thing by selecting the warmer of the two LED colors under consideration but the lighting industry is innovating rapidly to provide lights with less circadian-disrupting blue light while delivering high energy efficiency and a pleasant visual environment for people.  But putting color aside, Chicago is notorious in the international light pollution research community for being massively over-lit, with at least ten times the light emissions per capita as other cities like Berlin (a wealthy city with a similar population).  Chicago is not safer or healthier for all that extra light, no matter the color.  

Some residents, including the Chicago Tribune editorial board, may like the new lights, but that is beside the point.  Evidence, not instincts, should guide the choice of outdoor lighting.  Many things that feel good to some or are popular (like smoking) are bad for public health and outdoor lighting is no different.  No one should want the night lit up like the day and a return to a yellowish glow with next-generation LED systems that reduce impacts on human health, wildlife, and astronomy should be the goal for every community, small or large.  We’ve developed tools to assess and inform these decisions, policymakers just need to pay attention.

Travis Longcore, Ph.D.
January 4, 2020

Cover photo is taken by Tim Kopra (@astro_tim) in 2016, before the switch away from high-pressure sodium lighting.