light fixture 311.
(photo credit: Courtesy)
Avigayil Kadesh writes for NoCamels.
and starlight aren’t just romantic, according to a new international
study with Israeli input. This natural nighttime light is also healthier
than harsh artificial light – especially LED (light-emitting diodes)
white light, which suppresses the brain’s night time production of
Melatonin needed to regulate our biological clocks, behavior and health.
is beneficial, but dark is also beneficial,” says Prof. Abraham Haim,
head of the Center for Interdisciplinary Chronobiological Research at
the University of Haifa.
“We should live in darkness at night,
but since early human evolution one of the properties humans wanted to
change was the darkness. So we need to ask what type of illumination is
less harmful,” he adds.
That was the goal of the study, recently
published in the Journal of Environmental Management by Haim and other
researchers using data from astronomers, physicists and biologists at
the Light Pollution Science and Technology Institute in Italy and the
National Geophysical Data Center in Boulder, Colorado. Haim joined the
team about a year ago.
The scientists investigated the effect of
different types of outdoor lighting on light pollution and Melatonin, in
order to suggest practical steps for balancing productivity, energy
expenditure and public health.
White LED light (which is actually
blue light on the spectrum) is emitted at short wavelengths of between
440-500 nanometers. The study showed that this type of light suppresses
the body’s production of Melatonin five times more than the
orange-yellow light given off by traditional high-pressure sodium (HPS)
bulbs. Metal halide bulbs, often used for stadium lighting, suppress
Melatonin at a rate more than three times greater than the HPS bulb.
a problem, because Melatonin, which is made in the pineal gland at
night, is essential for biological rhythms and also has anti-oxidant and
anti-cancerous properties. At the same time, the brighter light causes
light pollution – obscuring the stars and disrupting ecosystems. One of
the study’s authors, Pierantonio Cinzano, is a world light pollution
However, LED is favored more and more because it doesn’t get as hot as HPS bulbs and therefore cuts energy consumption.
researchers make some concrete suggestions that could alter the
situation without throwing our world into total darkness. For example,
lampposts could be adjusted so that their light is not directed beyond
the horizon, which would significantly reduce light pollution. Most
importantly, they suggest what might be considered obvious: White light
should be limited to times and circumstances where it is absolutely
“We illuminate our world too much,” says Haim, who
admires how Italy dims its lights at night. “To save energy, let’s put
the lights off when we leave the room. We don’t have to use lighted
billboards overnight, and we don’t have to light up roads that are not
used heavily at night.”
Haim isn’t optimistic that any of the
recommendations will be adopted, due to all sorts of economic and
political realities. But he still wants to get out the message that “if
we would work only from 550 [nanometers] and higher, suppression of
melatonin would be less.”
In sleep studies done by one of his graduate students at the University
of Haifa, and also in Switzerland, people exposed to short-wavelength
LED lighting for two hours in the early evening did not experience the
normal nighttime reduction in alertness or body temperature, and their
Melatonin levels did not increase as they should have.
“When we used the same duration of exposure and the same intensity from
incandescent wavelengths of 550 or more, they did not get these
effects,” he says.
Ideally, Haim concludes, bulb manufacturers should be required to
disclose what wavelengths are produced by each bulb and how that might
affect melatonin production and light pollution.
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