University of Essex Prof. Arnold Wilkins, a leading expert in photosensitivity and physiology, has warned that energy-saving light bulbs could be giving us all headaches as they flicker too much. LED bulbs can bring on feelings of dizziness and pain within just 20 minutes of switching them on. They can also produce disturbing anomalies of perception, such as seeing multiple images of a lamp, every time you move your eyes rapidly.
Four fifths of British school children are having their learning impaired and are at risk from anxiety, migraines, headaches and even dyslexia from flickering lighting, he suggests.
“Unfortunately 80 per cent of our schools are still lit with lighting that flickers at 100 hertz”, he told a Lux conference on lighting fixture design in London in March. “It causes headaches and it causes anxiety. It’s there all the time. Whether it impairs their learning, seems to me to be plain enough.”
Although people can only directly perceive fluctuations at frequencies up to about 70 Hz, human vision is adversely affected by light fluctuations up to 200 Hz. Visual performance is especially degraded by flicker in the 100 Hz to 200 Hz range and in general, younger people are likely to perceive lower level and higher frequency flicker than older observers.
Wilkins, who directs the Visual Perception Unit at the University of Essex says, “there’s a huge range of susceptibility in the population with those [who get] migraines at one extreme. And it probably contributes to dyslexia but we don’t know for certain.
‘100 hertz should be avoided.’ The solution is to upgrade to high frequency control gear for fluorescent or LED. ‘It’s a simple as that.’
Flicker at 100 Hz is prevalent in older fluorescent light fittings with magnetic ballasts which were popularly installed in schools before the introduction of high-frequency electronic control gear and LED panels. Typically, magnetically ballasted fluorescent luminaires will exhibit flicker of between 10 and 20 per cent of output, and a ‘compact flicker degree’, or CFD, of over 20 per cent. Prolonged exposure leads to eyestrain, headaches and anxiety.
Most lighting is electric and powered by an alternating current supply, which makes the bulbs continually dim and then brighten again at a very fast rate. Unlike filament lamps and to a lesser extent fluorescent lamps, LEDs don’t just dim but effectively turn on and off completely (unless the current is maintained in some way).
“We know from earlier work on fluorescent lighting that even though the flicker is too fast to be visible, it remains a likely health hazard. In 1989, my colleagues and I compared fluorescent lighting that flickered 100 times a second with lights that appeared the same but didn’t flicker. We found that office workers were half as likely on average to experience headaches under the non-flickering lights.”
The flickering can be solved by buying a more expensive lamp, with a direct current rather than an alternating current so that the light is constant. But the lamp’s components may not last as long.