Environment

The difference between night and day is disappearing

The distinction between day and night is disappearing in the most heavily populated regions of the Earth, a rapid shift with profound consequences for human health and the environment, according to a paper published Wednesday in the journal Science Advances.

From 2012 to 2016, the artificially lit area of the Earth's surface grew by 2.2 percent per year. Bright nighttime lighting only started becoming widespread about 100 years ago, meaning we have little idea how humans or other species adapt to it at an evolutionary level. Light has been introduced in places, times and intensities at which it does not naturally occur and [for] many organisms, there is no chance to adapt to this new stressor.

The past few years have seen the rapid adoption of highly efficient LED lights for indoor and outdoor use. The short-wavelength blue light emitted by most LEDs, because our eyes are particularly attuned to this type of light, it's been implicated in sleep deficiencies and other human health problems. Last year, the American Medical Association issued a warning about health risks associated with this type of light.