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No need to be blue

Spotlight on LEDs

We have a tool for that

The newly-developed US Department of Energy Sky Glow Comparison Tool is a simplified method for comparing luminaire and control system contributions to sky glow, allowing the user to vary the output characteristics of each product being compared. This user-friendly tool was designed in 2018 to address a gap in the outdoor lighting design toolkit.

Bruce Kinzey, previous director of the US Department of Energy Municipal Solid-State Street Lighting Consortium, says that, importantly, the tool is not a model itself.

“Rather it enables the user to investigate relative impacts of different lighting characteristics by employing the results of
a model.

“It is most useful for gaining insight on the relative sky glow effects of different lighting characteristics, such as luminaire variations a site might be considering for a forthcoming conversion, via A-B type comparisons between them. The tool is comprised of a basic spreadsheet and is designed for use by members of the lighting community with inputs and outputs they can readily understand.”

Access a webinar on the tool’s uses at bit.ly/SkyGlowWebinar

Councils and road authorities have found themselves caught in the middle of a debate about the detrimental effects LED street lighting could have to human health and the environment. Lighting expert Bruce Kinzey says LED fears are widely out of proportion to their likely risk.

Many councils and road authorities are rightly choosing to embrace the energy savings and greenhouse gas reductions that large-scale LED roll-outs promise. However, news reports have emerged in recent years – some legitimate, many less so – about the potentially harmful effects of the blue wavelengths typical of broad-spectrum or ‘white light’ products like LEDs.

Stoked by the American Medical Association’s adoption of new guidelines in 2016 that warn against the use of broad-spectrum LEDs, communities have voiced concerns over the technology, creating a situation that could be difficult for local governments and road authorities to navigate.

Bruce Kinzey, previous director of the US Department of Energy (DOE) Municipal Solid-State Street Lighting Consortium (MSSLC), says the potential risks posed by street lighting have largely been overstated. He posits that the amount of blue light people are exposed to via street lights is – for the vast majority – far less than the amount delivered through other common sources, such as electronic screens.

“Unfortunately, one unintended consequence that can arise from LED street lighting changeovers is resistance from the general population regarding all short wavelength content from LEDs,” Bruce says.

“There is fear being spread – in our opinion widely out of proportion to likely risk – that in practice the blue wavelengths will harm our health and that of other species.”

Bruce was set to unpack the various stakeholder concerns and suggest effective methods for controlling and minimising blue wavelength light at IPWEA’s 4th International Street Lighting and Smart Controls Conference, in Sydney at the start of April.

He says his ultimate aim is to provide perspective about the technology’s relative risks and the massive opportunity it presents to help tackle the challenges of tomorrow.

“The world faces numerous challenges at present, not least climate change and its dire consequences that are forecast at existing levels of energy use,” Bruce says.

“Add to this the forecasts for continued global development, and the world clearly cannot afford to lose a single moment ramping up the deployment of technologies that facilitate our exit from traditional fossil fuels. Lighting typically comprises around 20 percent of the use of electricity in a modern economy, so is a substantial player in this critical endeavour.

“My dream is that the world rapidly comes to appreciate the importance of the reality we’re all facing and the relative risks and priorities get put into their proper perspective.”

Nothing new under the sun

He says there’s a common misconception that issues with blue light are new and coincide with the introduction of LED sources.

“The fact is that all broad-spectrum, or ‘white’ light sources contain at least some measure of blue wavelengths, including the sun and the moon’s reflection of it,” Bruce explains.

He points out that virtually all interior lighting sources in common use – including fluorescent, incandescent and LED – contain significant amounts of blue.

“In the outdoor environment, those same sources – plus mercury vapour and metal halide – have been used for decades, and in the case of incandescent, since electric lighting was invented.”

The only thing that’s truly ‘new’ is our heightened awareness and knowledge about blue light’s potentially negative impacts.

“Much of the perceived risk comes from the level of exposure, or ‘dose’, along with its associated timing in relation to an individual’s circadian clock,” Bruce says.

He explains preliminary survey-type research by the Pacific Northwest National Laboratory (PNNL) suggests that, under typical circumstances, the dose a person is likely to receive is much greater from indoor lighting in the home than exterior lighting infiltrating someone’s bedroom window.

“In a typical situation, a person is more likely to spend significantly greater time looking directly into a higher-intensity source of blue light, like a tablet computer or a television, often right up to the point they go to bed.”

However, he recognises that doesn’t mean there aren’t occasional cases where someone has a street light shining directly into their window.

“Citizens are justified in complaining about errant light entering their windows, but this is more of a light distribution than spectral content issue and changing the light to a warmer spectrum does not address it,” Bruce says.

“No one should, within reason, have to put up with street lighting of any spectrum shining directly into their window. Once that is eliminated, the indications are that the relative risk introduced by blue content in the source is minor compared to other light exposures.”

Minimising the effects

Even so, it’s still vital that the potentially negative impacts from broad-spectrum lighting are mitigated as much as possible. Bruce says there are a variety of methods available to minimise the impact LED streetlighting has on humans and the environment, and in fact LEDs offer more capabilities in this regard than any other mainstream lighting source invented to date.

“The methods involve preventing the various ecosystems from being exposed to electric light and blue wavelengths in particular,” he says, adding that, ideally, electric lights of any type should not be present in areas during periods they aren’t needed, such as sensitive wildlife habitats and people’s bedrooms.

He says that the US DOE published a study of LED street lighting’s effect on sky glow in 2017 that involved extensive use of a well-known sky glow model from the astronomical community (M. Kocifaj, Light-pollution model for cloudy and cloudless night skies with ground-based light source. Applied Optics, vol. 46, no. 15, 2007).

The study found that eliminating uplight – light emitted near or above a horizontal direction – had the greatest effect on reducing sky glow at a distance.

The second most important measure targets the light output level, Bruce says. “Reducing light levels has a directly scalar effect on sky glow. For example, dropping light levels in half, such as might be achieved by dimming after hours, reduces that source’s contribution to sky glow by half,” he says.

The third most important measure is altering the light source spectrum, especially if the choice is between two broad-spectrum or ‘white’ light options.

“Moving to a narrower-spectrum source, such as amber, can eliminate blue content entirely and thereby further enhance the reductions relative to broader spectrums.

“However, this also comes at a cost, notably increased energy use and reduced contrast and visual acuity relative to broad-spectrum sources, which may have negative safety implications.”

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