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LED street lighting is energy efficiency;
LED lighting can reduce energy
consumption by up to 50% compared
with conventional high pressure sodium
(HPS) lighting. LED lighting has no
warm-up requirement with a rapid ‘turn
on and off’ at full intensity. In the event
of a power outage, LED lights can turn
on instantly when power is restored, as
opposed to sodium-based lighting, which
require prolonged warm-up periods.
LED lighting also has the inherent
capability to be dimmed or tuned, so
that during off peak usage times (e.g.
1am to 5am), further energy savings can
be achieved by reducing illumination
levels. LED lighting also has a much
longer lifetime (15 to 20 years, or 50,000
hours), reducing maintenance costs by
decreasing the frequency of fixture or
bulb replacement.
“But depending on the design, a large
amount of blue light is emitted from some
LEDs that appear white to the naked
eye. The excess blue and green emissions
from some LEDs lead to increased light
pollution, as these wavelengths scatter
more within the eye and have detrimental
environmental and glare effects.
“The first generation of LED outdoor
lighting and units that are still widely
being installed are ‘4,000K’ LED units.
29% of the spectrum of 4,000K LED
lighting is emitted as blue light, which the
human eye perceives as a harsh white
colour. Due to the point-source nature
of LED lighting, studies have shown that
this intense blue point source leads to
discomfort and disability glare.
“More recently engineered LED lighting
is now available at 3,000K or lower. At
3,000K, the human eye still perceives
the light as white, but it is slightly
warmer in tone and has about 21% of its
emission in the blue-appearing part of the
spectrum. This emission is still very blue
for the nighttime environment but is a
significant improvement over the 4,000K
lighting because it reduces discomfort
and disability glare. Because of different
coatings, the energy efficiency of 3,000K
lighting is only 3% less than 4,000K but
the light is more pleasing to humans and
has less of an impact on wildlife.”
Disability glare is defined by the
Department of Transportation (DOT) as:
“when the introduction of stray light
into the eye reduces the ability to
resolve spatial detail. It is an objective
impairment in visual performance.”
“This glare can be greatly minimised by
proper lighting design and engineering.
Glare can be magnified by improper
colour temperature of the LED, such as
blue-rich LED lighting,” the AMA says.
“LED lighting is inherently a bright
point source and can cause eye fatigue
and disability glare if it is allowed to
directly shine into human eyes from
roadway lighting.
“Much has been learned over the past
decade about the potential adverse
health effects of electric light exposure,
particularly at night. The core concern
is disruption of circadian rhythm.
With waning ambient light, and in the
absence of electric lighting, humans
begin the transition to nighttime
physiology at about dusk; melatonin
blood concentrations rise, body
temperature drops, sleepiness grows
and hunger abates, along with several
other responses.
“It is estimated that a white LED lamp
is at least five times more powerful in
influencing circadian physiology than
a high pressure sodium light based on
melatonin suppression. Recent large
surveys found that brighter residential
nighttime lighting is associated with
reduced sleep time, dissatisfaction with
sleep quality, nighttime awakenings,
excessive sleepiness, impaired daytime
functioning and obesity.”
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.
Recognising the detrimental effects
of poorly-designed, high-intensity
LED lighting, the AMA encourages
communities to minimise and control
blue-rich environmental lighting
by using the lowest emission of
blue light possible to reduce glare.
The AMA recommends an intensity
threshold for optimal LED lighting
that minimises blue-rich light. The
AMA also recommends all LED lighting
should be properly shielded to minimise
glare and detrimental human health
and environmental effects, and
consideration should be given to use the
ability of LED lighting to be dimmed for
off-peak time periods.
The guidance adopted by grassroots
physicians who comprise the AMA’s
policy-making body strengthens the
AMA’s policy stand against light pollution
and public awareness of the adverse
health and environmental effects of
pervasive nighttime lighting.
Glare can be greatly minimised by proper lighting
design and engineering.