LEDs ‘making light pollution worse’

THE TRANSITION from sodium to LED exterior lighting over recent years appears to have made global light pollution worse not better, scientists have reported.

A team of researchers who studied Nasa images say that in the last four years the illuminated area of the earth grew by 2 per cent. The growth was most pronounced in developing nations.

While increasing prosperity accounted for part of that increase, the scientists believe LEDs are partly to blame.

Lead researcher Christopher Kyba from the German Research Centre for Geoscience in Potsdam told the BBC that the introduction of artificial light was ‘one of the most dramatic physical changes human beings have made to our environment’.

The team had anticipated a decrease in brightness in developed and industrial areas as orange sodium were replaced with LEDs, but in fact the reverse happened.

‘I expected that in wealthy countries - like the US, UK, and Germany - we'd see overall decreases in light, especially in brightly lit areas,’ he told BBC News. ‘Instead we see countries like the US staying the same and the UK and Germany becoming increasingly bright.’

To make matters worse, the light sensor on the satellite – a radiometer – is not able to measure the bluer part of the spectrum of light that LEDs emit, meaning that visible light pollution is even worse than that measured.

‘Because there is more blue light in LEDs than in sodium, it’s more liable to be scattered due to the Rayleigh effect,’ said Lux technical editor Alan Tulla. ‘An additional factor would be the combination of increased prosperity in developing nations and the falling prices of LED luminaires globally.’

The findings are certain to increase the pressure on the lighting industry to take light pollution seriously and improve the optics and upward light control.

The researchers published the findings in the journal Science Advances.

Comments 10

Mark, I disagree on this one the very directionality of LED and the tendency to use innapropriate CCT to misguidedly "drive" further efficacy is part of the problem, as it the much higher scatter of blue wavelength that's the main issue here. There is much to be said when lighting a 3D space especially in a nocturnal environment to light with a lower intensity source. If anyone doubts it just look at the effect of viewing a few isolated streets from above lit with LED compared to more conventional sources, it really does show up the challenges of delivering with LED. We have much to understand, current fixture design certainly leaves much to be desired and we also need to account for the impacts of aged driver response, much poorer Weather performance, Glare and scatter is also very enhanced when of moving to sources with considerably higher short wave spectrum when lighting the exterior space

People will always express their opinions on something new. One has to see everything in the right perspective. People will always find something to criticize. LEDs are more efficient than other man-made types of light sources. They consume much less electricity than previous light sources, and therefore reduce pollution caused by electricity generation equipment. They are usually directional and concentrate the light to where it is required. Regarding the blue aspect, that depends on which type of LEDs are used. To describe this as pollution is absurd. These light sources are useful so that people can be constructive and also be safe.

Certainly the problem is not due to the LED light source, since LEDs are more directional than most light sources, except for Lasers, but rather because of inadequate designs or incorrect installations. Of course there is now, in addition, the infatuation with adding illumination to the outside of structures, where it was not an option with prior lighting technology. In addition, it is far less power consuming than prior means, decreasing the cost of a lot more light. AND, of course, there is the proliferation of lighting in many parts of the world due to the rise in their standard of living and increased prosperity. Allowing worthwhile activities to happen safely during darkness hours is a real benefit from the LED lighting revolution.

LEDS are wonderful but does not change the need to practice good lighting. Artificial light is a tool and Bigger, better, stronger works both ways if not used correctly.

Considering the overall efficiency of LEDs: 10 times better than incandescent and, quite 2 time more than fluorescent, we should observe CO2 emission reduction. Because of increased efficiency of LED, the reduction of temperature of illumination devices reduce the IR emission.

When the LED lights were becoming a viable thing there was a lot of articles around about the ability of reducing the amount of scattered light. The problem seems to be cheap poorly designed light fittings and the purchasing and installation of unsuitable lights for the situations.

A good illustration of the Jevons Paradox.

In addition to the fashion for floodlighting the outside of buildings there is lots of light coming from office and shop windows in cities. More trunk roads and motorways have lighting than in the past. So it is not reasonable to put all the blame on moving to LEDs.

I totally agree with Mark Saunders, supplementing: the Jevons Paradox is happening again! Leds are, not only in 'standard' streetlighting, they are in places where never was light before. Complete buildings are now surrounded with (programmable) leds, Although the owners shout out loud the used technoly and leds are very low energy use, all are extra added features, which were a few years ago not there and impossible, Conclusion: extra light and extra energy use although the leds are otherwise designed: the Jevons Paradox of leds.

I think they're barking up the wrong tree here. There's nothing in the technology that would increase light pollution as opposed to discharge lamps used in the same way. Has anyone ever seen a led roadway light that wasn't a full cut-off design? If there is an increase in light pollution, it is, as Alan Tulla said, due to increased prosperity and lower prices equalling more installations.

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