The shift to unsafe high-blue lights is simply a matter of forgetting what was figured out. In the 20th century the lighting companies (GE, etc) had all the money in the world, and spent a lot on R&D. They figured out how to get the most efficient lights possible for their customers. The scientists figured out exactly how blue light causes inflammation in our eyes. There are good reasons why cities used orange High Pressure Sodium [HPS] Bulbs for street lights: HPS is very energy efficient (as good as most LEDs), and they emit light that is almost blue-free.<p>Then LEDs were invented by companies that didn't have that old R&D. The automotive industry gradually switched to LEDs for the advantage of not needing to replace bulbs (but lights that fail are now >$1000 to replace instead of $5)<p>Instead of putting safe low-blue LEDs on their cars (~2400K), auto manufacturers are using 4000K to 5000K LEDs. These have too much blue light.<p>To understand modern lighting, the term "spectral power distribution" is quite helpful: <a href="https://en.wikipedia.org/wiki/Spectral_power_distribution" rel="nofollow">https://en.wikipedia.org/wiki/Spectral_power_distribution</a><p>Relative Spectral Power Distribution graphs show how much of each color of the rainbow is in a given source of light. Incandescent bulbs are mostly Red-orange-yellow light with a bit of green and even less blue. 5000K fluorescent or LED bulbs are mostly blue light with just enough red orange and yellow to trick people into thinking the light is 'white'.<p>I emailed Daniel Stern a few years ago and asked, essentially, 'why aren't auto manufacturers putting safe lights on their cars?' The essence of his reply was that the automotive engineers still know how to design safe headlights, but there were other considerations in play. I took this to mean that the marketing department told the engineers, "cars with safe headlights don't sell anymore, so you need to design headlights with blue-white LEDs." Daniel's response also helped me realize that the worst of the headlights on the road in 2017 were LED retrofits, where people bought LEDs to replace the halogen bulbs their vehicle's headlights were designed to use.<p>The shift to unsafe lights started in the 80's or 90's, when luxury brands started putting High Intensity Discharge lights on their vehicles. These lights have more blue light than the old incandescent and halogen headlights. Headlights with more blue became associated with more expensive cars, even though blue light is terrible for humans at night.<p><a href="https://en.wikipedia.org/wiki/High-intensity_discharge_lamp" rel="nofollow">https://en.wikipedia.org/wiki/High-intensity_discharge_lamp</a><p>Daniel has a webpage about how France used to require yellow headlights: <a href="https://www.danielsternlighting.com/tech/lights/light_color/light_color.html" rel="nofollow">https://www.danielsternlighting.com/tech/lights/light_color/...</a><p>The rest of Europe didn't require yellow headlights, and there was a problem of having to put cadmium in the glass, so France got rid of their requirement.<p>I submitted an AskHN a few years ago, but it didn't get much traction: <i>Ask HN: What prevents the automotive industry from using safe LEDs?</i> - <a href="https://news.ycombinator.com/item?id=27334405">https://news.ycombinator.com/item?id=27334405</a><p>In 2020 I sat down to think about why blue light at night is so terrible, and sort of figured it out.