“There is no such thing as a free lunch,” biologist Barry Commoner wrote in 1971, proposing that as one of four “laws of ecology.” We’ve had decades to absorb that lesson but it still comes hard. Each technological innovation tempts us anew to think we’ll get something for nothing – an advance with all benefits and no costs.

LED (light-emitting diode) lights looked at first like they might qualify. After years spent enduring the odd shapes, harsh light and slow starts of compact fluorescent bulbs (not to mention risking mercury exposure if they broke), we were ready for a breakthrough in energy-efficient lighting.

It came with the speed and brilliance of a lightning bolt. The adoption of LED bulbs represents one of the fastest technological transitions ever. And for good reason: The best LED bulbs use 85 percent less electricity than their incandescent counterparts and last up to 25 times longer.

LED bulbs reduce demand for electricity, which cuts back markedly on the greenhouse gas emissions fast cooking the planet. The National Oceanic and Atmospheric Administration reports that 16 of the hottest 17 years on record have occurred since 2000, with 2016 topping all previous records.

The long lifespan of LED bulbs leads to fewer replacements, reducing labor costs and resource consumption – on top of electrical savings. Within a decade, U.S. consumers and businesses could be saving $20 billion a year from LED technology.

With all these environmental and economic benefits wrapped into bulbs that turn on instantly, can be dimmed and can withstand cold, what’s not to like?

Too much evening exposure to LED lights can make it harder to get to sleep.

The unforeseen cost of this lunch lies in the potential health impacts of LED lights, for humans and wildlife.

Light in all forms influences circadian rhythms, innate cycles that govern sleeping and eating as well as functions like brain activity and hormone production. These physiological patterns are disrupted far more by the blue wavelengths that dominate LED lights than by warmer-toned incandescent lamps.

LED lights outdoors have a similar adverse effect on wildlife, upsetting established behaviors and migratory patterns in birds, insects, turtles and fish.

For our own species, naturally occurring blue light that we experience outdoors in daytime can boost mood and attention. But exposure to those same wavelengths from LED lights at night suppresses melatonin, making it harder to get to sleep.

Studies indicate that ongoing exposure to certain bands of blue light may damage the eye’s retina and macula, contributing to problems like age-related macular degeneration. Even short-term exposure to high-intensity LED lights can cause discomfort.

To keep health risks to a minimum, we need to get brighter in our use of LED bulbs.

CHOOSE OUTDOOR LIGHTING WISELY

Communities that upgrade to LED streetlights and individuals choosing LED outdoor lighting need to do adequate research. The American Medical Association recently issued a policy recommending that streetlights have a color temperature of 3000 Kelvin or less. High-intensity lights that range from 4000-5000 Kelvin are associated with more glare, wildlife disruption and light trespass into nearby residences.

Bad side effects can be minimized by what is known as “full cutoff” or “shielded” light fixtures that direct light downward. “Night-friendly” fixtures reduce the artificial sky glow that dominates metropolitan areas and prevents 80 percent of North Americans from seeing the Milky Way. A look at an atlas of artificial brightness in the night sky published last year in the journal Science Advances reveals the far reach of light pollution.

Since LED lights are brighter than incandescent bulbs, it’s important to minimize their number and intensity outdoors. Communities can further reduce negative side effects and electrical expenditures by installing fixtures that allow bulbs to be dimmed at periods of low use.

Towns and cities in Maine now have more incentive to upgrade to LED bulbs, thanks to a 2011 state law that allows communities to own and maintain their own streetlights rather than leasing them from utilities. Typically, electrical savings from installing LED street lights more than cover project and financing costs. Many Maine communities have avoided an upfront investment by working with an energy service company and/or a third-party financing specialist (which funds the upgrade and is repaid through energy savings).

AVOID USE NEAR BEDTIME

Communal decisions about LED lighting take time for planning and budgeting. But within our homes, we can make changes literally overnight. The medical guidance is clear: reducing (or better yet eliminating) LED use within an hour or two of bedtime will likely improve sleep.

That may be a big adjustment for those accustomed to evening use of smartphones, tablets, desktop computers, LED televisions and e-readers. If you can’t always manage a pre-bed LED fast, try installing free software, such as f.lux, that changes LED screens to warmer color tones during night hours.

LED bulbs are a welcome advance with great potential to cut greenhouse gas emissions, save resources and reduce ambient light pollution. We just need to be smart about their use so we can enjoy their benefits at the least possible cost to our health and to natural communities.

Marina Schauffler is a writer whose work is online at naturalchoices.com.