Light pollution has not occupied the limelight like water and air pollution. Even people who religiously recycle their waste and try to minimize their carbon footprint are often unaware of this silent enemy. Yet the impact of this lesser known evil is no less than its more famous peers.

Sample some data

Depending on the type of light employed, wastage of light form a street light ranges between 0 % for LED street lights to 70% for some types of decorative light fixtures. Whether you are using mercury vapor lamps, metal halide bulbs, HPS or LPS lamps 30 to 70% of the light produced by the bulb is used to illuminate the sky, stars, clouds, insects and birds! For a 28000 lumen light fixture this translates to 8400 lumen of wasted light! Most street light fixtures in United States are of the HPS variety that consumes 250 watts per hour. At this rate of power consumption the wastage translates to 27 $ per street light per annum. For a city like Los Angeles alone with 209,000 street lights electricity worth $ 5,721,375 is directed towards the sky!

There are an estimated 35 million street lights in United States and the $ value of the electricity wasted works out to a stupendous $ 958,125,000! All this is public money collected from tax payers. Instead of making life difficult for scientists, killing insects and damaging the environment, this money could provide employment to 19,162 people at an annual salary of $ 50,000. Clearly, light pollution is not just about dark skies and the environment alone.

Besides wasting light what else does light pollution do?

Reduced visibility – Light that is not directed downwards strikes the eyes of the viewer horizontally, thereby, increasing glare and reducing clarity of vision.

Over lighting – If a large percentage of the light is wasted more powerful lights will be needed to achieve the objective of sufficient illumination. If light pollution were curtailed a 2000 lumen light could easily substitute one producing 2800 lumens. LED lights that direct all their output downwards are, therefore, more efficient than either LPS or HPS lamps.

With decorative fixtures the savings can be much more. Decorative fixtures that are open at the top waste up to 70% light. Many more poles need to be erected to provide sufficient light on the ground. The cost of the additional poles and wiring thus gets added to the cost of lighting.

Each additional pole costs around $ 4000 to install! Lighting engineers have realized the need to curb the wastage and are increasingly recommending directional Light Emitting Diode based lights.

Impact on Biological Rhythms – Animals and plants have a 24 hour cycle programmed into their genes by millions of years of evolution. Human beings for example secrete more growth hormone during sleep. 10 – 15% of human genes are believed to be affected by light! The deleterious impact of unwanted light on delicate biological systems is to be expected. A hormone Melatonin is secreted by the pineal gland. This hormone is responsible for reducing the amount of estrogen secreted at night. Excess light is thus linked to lower melatonin levels resulting in higher estrogen secretion, premature puberty and has also been implicated in breast and prostate cancer. No time of the day is now suited for nocturnal insects. Devoid of their predator detection system they have lost the ability to evade their predators. This in turn has serious consequences for not just insects but their predators too. Research has demonstrated that a million insects are killed due to the 50,000 street lights of Zurich. You can extrapolate to estimate the impact of the 35 million street lights in the United States. 

Combating Light Pollution

The fix for Light pollution is surprisingly easy. Here are the options

1)    Install protective skirting around existing lamps
2)    Install box type lamp shades that direct light downwards
3)    Install LED based outdoor lights

The cost of material, manpower to rental cost of equipment to install either a skirting or box shaped lamp shades is US $ 800 - 900 per light. No benefit other than reduced light pollution and more available light on the ground is forthcoming from this exercise. Future maintenance and energy consumption remain unaffected. It is far better to replace HPS lamps with LED lighting devices that by design direct light downward, consume 30 to 70 % less energy and provide high quality full spectrum light.

LED lights provide the ultimate answer to light pollution. Ideally, a street light should have a wide cone of light around 120 degrees wide but no light should be directed above the horizontal. Given that LED street lights have a large angle of 150 degrees to optimize illuminated ground area, this aim is easily attained with these energy efficient lamps.

Many adopters of LED technology have done so to eliminate the hassle of replacing bulbs. Given their long life these are semi permanent light fixtures. With LEDs there is never a dark moment. Made of a cluster of light producing devices these fail gradually over a period of time and the likelihood of all the LEDs failing together is very remote.

Intelligent Lights for a Smarter World

Full spectrum light, excellent color rendition, high lumen per watt consumed, wide angle of light, zero wastage of light,  zero mercury pollution, no moving parts or fragile filaments, very little risk of breakage, low power consumption, ability to transmit data and facilitate networking, possibility of remote management and intelligent controls, possibility of changing light output to optimize power consumption and visibility, possibility of changing light color on the basis of ambient light color to maximize contrast and enhance visibility – LED lighting systems are the holy grail of lighting technology on more ways than one.