High-intensity LED lights can impair health, AMA warns

If people are "sleepless in Seattle", as the movie title says, it may not be only because they have broken hearts.

The American Medical Association issued a warning in June that high-intensity LED streetlights - such as those in Seattle, Los Angeles, New York, Houston and elsewhere - emit unseen blue light that can disturb sleep rhythms and possibly increase the risk of serious health conditions, including cancer and cardiovascular disease. The AMA also cautioned that those light-emitting-diode lights can impair night-time driving vision.

Similar concerns have been raised over the past few years, but the AMA report adds credence to the issue and is likely to prompt cities and states to re-evaluate the intensity of LED lights they install.

Nearly 13 per cent of US area / roadway lighting is now LED, according to a report prepared last year for the Department of Energy, and many communities that haven't yet made the switch plan to do so. LEDs are up to 50 per cent more energy-efficient than the yellow-orange high-pressure sodium lights they typically replace. They last for 15 to 20 years, instead of two to five. And unlike sodium lights, the LEDs spread illumination evenly.

Some cities say the health concerns are not convincing enough to override the benefits of the first-generation bright LED lights that they installed in the past three to eight years. New York is one of them, although it has responded to resident complaints by replacing the high-intensity, white LED bulbs with a lower-intensity bulb that the AMA considers safe.

Scott Thomsen, a spokesman for Seattle City Lights, which is responsible for the city's exterior illumination, dismissed the health concerns about bright-white LED lights, noting that they emit less of the problematic blue wavelengths than most computers and televisions.

After a year and a half of discussion and sampling, Lake Worth, Florida, is replacing its sodium streetlights with about 4,150 LED lights with an amber glow. ''We found a colour that made sense for the health of our city, and we're proud of the choice we've made,'' Michael Bornstein, the city manager, said.

Mark Hartman, Phoenix's chief sustainability officer, said the city might go with a mix of the intense lights for major intersections and ballpark areas that need very bright light and a softer light for residential areas. He said the city would consider the health arguments, although he too mentioned the glow from computers and televisions. ''Nobody says don't watch television or use your computer after 9 pm because of blue lights,'' he said.

Almost as soon as outdoor LEDs were made available, the federal government encouraged states and municipalities to use them, calling LEDs highly efficient for applications such as traffic lights and exit signs. But critics say federal authorities were too quick to endorse LEDs.

The Department of Energy and the Environmental Protection Agency ''put a lot of push into them'', said Michael Siminovitch, director of the California Lighting Technology Center at the University of California at Davis. ''I call it a rush.''

Siminovitch said the light from early-generation LEDs ''really negatively impacts people's physiological well-being''.

Lighting is measured by colour temperature, which is expressed in ''kelvin,'' or ''K.'' The original LED streetlights had temperatures of at least 4000K, which produces a bright white light with a high content of unseen blue light.

Now, however, LEDs are available with lower kelvin ratings and roughly the same energy efficiency as those with higher ratings. They don't emit as much potentially harmful blue light, and they produce a softer, amber hue.

When 4000K and 5000K LEDs were installed, they drew mixed responses. Police and traffic-safety officials and many motorists liked them because they created a bright light that sharply illuminated the ground they covered.

But in many places, including New York City and Seattle, residents complained that the bright white light they emitted was harsh, even lurid. People described them as invasive, cold and unflattering.

Even before the AMA warning, some researchers raised health concerns. Some noted that exposure to the blue-rich LED outdoor lights might decrease people's secretion of the hormone melatonin. Secreted at night, melatonin helps balance the reproductive, thyroid and adrenal hormones and regulates the body's circadian rhythm of sleeping and waking.

''As a species, we weren't designed to see light at night,'' Siminovitch said.

Meanwhile, the ''dark sky'' movement criticizes LEDs as a major contributor to what it calls the ''light pollution'' that humans cast into the night sky.

In its warning, the AMA cited the melatonin issue, noting that studies have linked bright LEDs to reduced sleep time, poor sleep quality and impaired daytime functioning.

It referred to evidence that exposure to high-intensity light at night might increase the risk of cancer, diabetes, cardiovascular disease and obesity. And it cautioned that intense LEDs have been associated with ''discomfort and disability glare,'' which might impair night-time vision for drivers.