BENCH TEST / LED MODULES
The advent of LED lighting has opened an age old debate about whether artificial lighting is healthy and safe from a human perspective. This month Dr Geoff Archenhold will attempt to get beneath the surface of the arguments about some of the factors that impact on human vision.
HEALTH AND SAFETY OF ARTIFICIAL LIGHTING
The use of artificial lighting has always sparked controversy about how healthy the emitted light is and whether that light is safe for humans. For example, warnings from the Health Protection Agency regarding single envelope CFL lamps and excess UV light exposure to the fears posed by the French Agency for Food, Environmental and Occupational Health & Safety (ANSES) study into a few LED lights that create a blue light hazard. The key issue facing the lighting industry is should it put healthy and safe lighting high on its agenda when designing lighting schemes and manufacturing lighting products or should price and ignorance of the issue prevail!
The lack of knowledge on healthy and visually safe lighting is prevalent and the effects are rarely discussed outside academic circles so we have an awful long way to go to put quality lighting first. I will attempt to scratch the surface of some of the key health and safety issues with artificial lighting with the aid of several published documents reviewing the issues.
Optical Radiation
The use of artificial lighting has laid claim to a wide range of light sensitive symptoms that are aggravated by their use including: • xeroderma pigmentosum • lupus • migraine • epilepsy • myalgic encephalomyelitis (aka chronic fatigue syndrome)
• Irlen-Meares syndrome (aka scotopic syndrome)
• fibromyalgia • electrosensitivity • dyspraxia • autism/asperger syndrome • retinal diseases, such as age-related macular degeneration (AMD)
• chronic actinic dermatitis, • solar urticaria
Figure 2: Various light source and eye response spectrums.
It has been estimated by the Scientific Committee on Emerging and Newly Identified Health Risks (SCENIR) in a worst case scenario that approximately 250,000 individuals within the EU (some 0.05% of the population) might be at risk from increased levels of UV/blue light optical radiation. However, it is not just the few that suffer significantly from elevated optical radiation systems. Recent work has shown several light sources produce more harmful optical radiation than others.
The Basics Visible light is defined as the electromagnetic radiation with wavelengths between 380nm and 750nm which is mostly detected by the human eye. Electromagnetic radiation exists from gamma rays right through to radio waves as shown in figure 1 with the visible wavelengths occupying a small section of the spectrum. In addition to wavelength, light can also be characterised quantitatively by its intensity.
Figure 1: The colour spectrum.
The ultra-violet portion of the spectrum (fig 1) can be particularly dangerous to humans and is usually divided into three regions: UVA (315nm – 400nm) UVB (280nm – 315nm) UVC (100nm – 280nm) Thankfully, natural sunlight is attenuated as it travels through the earth’s atmosphere which means most of the radiation with a wavelength below 290nm is filtered out before it reaches the surface. Each artificial light will have its own unique characteristic fingerprint and that is often referred to as the Power Spectral Density (PSD) or spectrum curve which identifies the amount of radiant energy
TECHNOLOGY / LED 111
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