Invention and production of Light-Emitting Diodes (LEDs) as a source of lighting has been received by people with high esteem due to their long life (about 20 years or so) and role towards saving on electricity and environment.  LEDs use significantly less energy than even CFLs, and do not contain mercury and are becoming economically competitive with CFLs at the point of purchase while yielding superior quality lighting and energy bill savings down the line.

However, LED bulbs were costly in the beginning but with time and technology developments they are becoming cheaper and governments are encouraging people to cut their energy use and thus contribute towards sustainable environment. Within last few years, use of LED bulbs and streetlights has sprung up in the houses, offices and on the roads all over the world. Thus, converting conventional light to energy efficient LED lighting leads to cost and energy savings, and a lower reliance on fossil-based fuels. Strong arguments exist for overhauling the lighting systems with light emitting diodes (LED), but conversions to improper LED technology can have adverse consequences.

Dangers of  LEDs

Because of their circuitry, LEDs are not always compatible with traditional dimming switches. In some cases, the switch must be replaced. Other times, you'll pay a little more for a compatible LED. Not all light fixtures should use LEDs. You probably know that LED bulbs run dramatically cooler than their incandescent cousins, but that doesn't mean they don't produce heat. LED bulbs do get hot, but the heat is pulled away by a heat sink in the base of the bulb. From there, the heat dissipates into the air and the LED bulb stays cool, helping to keep its promise of a very long life. And therein lies the problem: the bulb needs a way to dissipate the heat. If an LED bulb is placed in an enclosed housing, the heat won't have anywhere to go, sending it right back to the bulb, and sentencing it to a slow and painful death. Additionally, all LEDs are made with either the element gallium (Ga) or indium (In), and both of those are not very abundant on this planet. That leads to questions about sustainability for something produced in 100s of millions of units, like light bulbs.

The issues of most concern identified concern the eye due to the toxic effect of blue light and the risk of glare adding that the blue light necessary to obtain white LEDs causes "toxic stress" to the retina. Blue light causes a photochemical risk to the eye the level of which depends on the accumulated dose of blue light to which the person has been exposed, which is generally the result of low-intensity exposure repeated over long periods. Blue light is recognized as being harmful and dangerous for the retina, as a result of cellular oxidative stress. The other main risk is from glare. For indoor lighting, it is generally agreed that luminance higher than 10,000 cd/m² causes visual discomfort whatever the position of the lighting unit in the field of vision because the emission surfaces of LEDs are highly-concentrated point sources, the luminance of each individual source can be 1000 times higher than the discomfort level. The level of direct radiation from this type of source can therefore easily exceed the level of visual discomfort.

Ever since the LED streetlights have been installed, people have been complaining about glare, light pollution, and their effects on wildlife. Therefore, people those who have early-adopted the use of LED bulbs and streetlights are now faced with a problem: they don’t like the light. LED streetlights come with a bluish tinge which may be unwelcome—or even unhealthy for human exposed to these LED lights. The reason that LED lighting often looks so blue is one of efficiency. Blue LEDs—the invention of which snagged a Nobel Prize—are more energy-efficient than those of any other color. So white LEDs are actually blue LEDs with added materials that absorb some blue light to re-emit it as yellow. While it’s possible to warm the light further by adding more of the material, that also decreases efficiency. To keep costs down, many cities chose to keep things at the blue end of the spectrum. A study also found that LEDs contain lead, arsenic and a dozen other potentially dangerous substances.

It is now accepted that artificial night-time lighting has various effects on humans (not to mention wildlife) and that exposure to optical radiation affects human physiology and behavior, both directly and indirectly. Report emphasizes the risks of LED lighting and makes various recommendations. American Medical Association  (AMA) explained that blue-tinged street lamps “create worse nighttime glare” and “have five times greater impact on circadian sleep rhythms” than conventional street lamps. AMA has already adopted guidance for communities on selecting among LED lighting options to minimize potential harmful human and environmental effects. AMA guidance encourages proper attention to optimal design and engineering features when converting to LED lighting that minimize detrimental health and environmental effects. High-intensity LED lighting designs emit a large amount of blue light that appears white to the naked eye and create worse nighttime glare than conventional lighting. Discomfort and disability from intense, blue-rich LED lighting can decrease visual acuity and safety, resulting in concerns and creating a road hazard. In addition to its impact on drivers, blue-rich LED streetlights operate at a wavelength that most adversely suppresses melatonin during night. It is estimated that white LED lamps have five times greater impact on circadian sleep rhythms than conventional street lamps. Recent large surveys found that brighter residential nighttime lighting is associated with reduced sleep times, dissatisfaction with sleep quality, excessive sleepiness, impaired daytime functioning and obesity.

The detrimental effects of high-intensity LED lighting are not limited to humans. Excessive outdoor lighting disrupts many species that need a dark environment. For instance, poorly designed LED lighting disorients some bird, insect, turtle and fish species, and national parks in some countries have adopted optimal lighting designs and practices that minimize the effects of light pollution on the environment.

Solutions in future

Recognizing the detrimental effects of poorly-designed, high-intensity LED lighting, the AMA encourages communities to minimize and control blue-rich environmental lighting by using the lowest emission of blue light possible to reduce glare.

• LED manufacturers have been trying to solve the problem by creating higher-efficiency red LEDs that can be added to balance the light out.
• The AMA recommends an intensity threshold for optimal LED lighting that minimizes blue-rich light.
• The AMA also recommends all LED lighting should be properly shielded to minimize glare and detrimental human health and environmental effects, and consideration should be given to utilize the ability of LED lighting to be dimmed for off-peak time periods.
•  Manufacturers and integrators of lighting systems using LEDs are encouraged to use optics or diffusers, for example, so that the beams of light emitted by the LEDs cannot be seen directly, to avoid glare.
• Manufacturers should also take account of the progressive wear of layers of phosphor in white LEDs, which in time could lead to devices being moved from one photobiological risk group to a higher one.

Conclusion

An incandescent bulb has a color temperature (CT) of 2400K, which means it contains far less blue and far more yellow and red wavelengths. Before electric light, we burned wood and candles at night; this artificial light has a CT of about 1800K, quite yellow/red and almost no blue. The new "white" LED street lighting which is rapidly being retrofitted in cities throughout the country has two problems. The first is discomfort and glare. Because LED light is so concentrated and has high blue content, it can cause severe glare, resulting in pupillary constriction in the eyes. Blue light scatters more in the human eye than the longer wavelengths of yellow and red, and sufficient levels can damage the retina. This can cause problems seeing clearly for safe driving or walking at night. The other issue is the impact on human circadian rhythmicity. There is almost never a completely satisfactory solution to complex problems. We must have lighting at night, not only in our homes and businesses, but also outdoors on our streets. The need for energy efficiency is serious, but so too is minimizing human risk from bad lighting, both due to glare and to circadian disruption. LED technology can optimize both when properly designed.

Acknowledgement: The use of information retrieved through various references/sources of internet in this article is highly acknowledged.