What, is there a correlation between LED lighting
and human health?
The adoption of LED lighting in the South African and Sub-Saharan lighting market has been growing at a
phenomenal rate. Up till now, over 15% of the outdoor lighting in South Africa is powered by LED’s. This
mainly attributed to the energy efficiency benefits and increased lifetime of LED luminaries. On the other
hand there has been rising concerns created by an article published on an international platform
highlighting the risk of LED lighting and the impact LED lighting has on the human health while also raising
concern about the glare aspects of LED light sources.
The American Medical Association (AMA) makes three core recommendations in its new policy statement:
1. First, the AMA supports a “proper conversion to community based Light Emitting Diode (LED) lighting,
which reduces energy consumption and decreases the use of fossil fuels.”
2. Second, the AMA “encourage[s] minimizing and controlling blue-rich environmental lighting by using the
lowest emission of blue light possible to reduce glare.”
3. Third, the AMA “encourage[s] the use of 3000K or lower lighting for outdoor installations such as
roadways. This is because of a belief that LED lights that appear too blue can suppress melatonin
production, which can lead to increased diabetes and depression. All LED lighting should be properly
shielded to minimize glare and detrimental human and environmental effects, and consideration should
be given to utilize the ability of LED lighting to be dimmed for off-peak time periods.”
BEKA Schréder certainly agrees that any streetlight installation should be designed in such a way that it
complies with the national road lighting requirements by means of complying to lighting levels, uniformity
and glare ratings. We however have no reason to agree with is the recommendation to only use 3000K or
lower colour temperature on street light applications.
The concerned article does not specify if there was a scientific research conducted to support the
recommendations made by the AMA. It might be correct that the blue content of light sources has an effect
on the circadian rhythm but we have to acknowledge that the exposure of every human being to “white light”
within your everyday activity such as TVs, car headlights, computer screens and smartphones is much higher
nowadays far higher than the exposure to street lights. We certainly agree that colour temperatures of light
sources higher than 5000K should be avoided primarily because the colour rendering coefficient mostly
decreases when using light sources with high colour temperatures.
HEALTH EFFECTS OF LED LIGHTING |
The advantages of color temperatures
between 3000K and 5000K outweigh those
of any other color temperature as the true
color reflection is very close to how we
perceive color during the day and therefore
sense a feeling of security and well being.
The article also mentions that incandescent
light sources seem to be the reference but
the circadian rhythm is certainly not aligned
to
the
spectral
distribution
of
an
incandescent lamp but rather to that of the
moon light and sun light. The spectral
distribution of the moon has a very high blue
content and therefore much closer to that of the LED light source compared to that of an incandescent. The
rods within our eyes are active in those low level light environments and therefore are more sensitive to light
with a higher blue content which therefore results in a higher visibility at night time. See Figure above, 1 and
Figure 2 the eye sensitivity curve during day (photopic) and night (scotopic) and light level perception.
The circadian rhythm is much more affected by the amount of light (luminance levels) which is generally
very low on residential street lighting. Therefore high exposure to cool white light and high light levels is
very limited on street lighting but much higher on computer screens or smartphones or TV screens.
Many LED installations appear to be glarier than conventional high pressure lamp installations. Mostly the
LED technology is given blame for this even though it is actually not the case.
HEALTH EFFECTS OF LED LIGHTING |
Glare can be generally divided into two types, discomfort glare and disability glare. Discomfort glare results
in an instinctive desire to look away from a bright light source or difficulty in seeing a task. Disability glare
impairs the vision of objects without necessarily causing discomfort. This could arise for instance when
driving westward at sunset.
Disability glare is often caused by the inter-reflection of light within the eyeball, reducing the contrast
between task and glare source to the point where the task cannot be distinguished. When glare is so intense
that vision is completely impaired, it is sometimes called dazzle
With LED installations the discomfort glare is most applicable as the LEDs are designed to emit the same
amount of light as conventional bulbs from a smaller area, which could possibly increase the discomfort glare.
In addition, white LEDs typically have more energy in the blue part of spectrum, which can also cause more
glare because blue light is perceived brighter by the human eye under the same light levels, as mentioned
earlier.
This is one of the reason why BEKA Schréder spreads the amount of light emitted by the LEDs over a higher
number of LEDs as this will increase the light emitting surface area and why we design dedicated optics for
different road geometries to minimize the discomfort glare. Further to this we limit ourselves to a maximum
color temperature of 5000K. By implementing this, the discomfort glare is equivalent to any conventional
street light installation.
To summarize the pros and cons the following Table 1 should assist:
Table 1
Description
HPS System
MH System
LED System
Efficiency (lm/W)
≤120lm/W
≤100lm/W
≤130lm/W
CCT (K)
2000-3400
3000-4200
2700-6000
CRI (Ra)
≤25
≤95
≤95*
Spectral distribution
Poor
Good
Good
Lifetime (hrs, L70)
≤16 000
≤12 000
≤100 000
Thermal feedback
No
No
Yes
Dimming
Partly
Yes
Yes
HEALTH EFFECTS OF LED LIGHTING |
Light utilization
Average
Good
Very Good
Optic variety
Limited
Limited
High
Yes both
Yes, safety, performance
Standards
available-safety Yes both
and performance
soon
Glare
Turn
on
time
to
Low
Average
Average
full 6-10min
1-3min
Instant
Limited
Yes
brightness
Instant restrike
Limited
*Depending largely on efficiency and lifetime, the higher the efficiency, the lower the CRI and lifetime.
To conclude, it must be said that the LED streetlight installations are certainly not harmful to society. The
exposure to other light sources with much higher blue content is much more. The increased visual
improvements and the higher feel of safety while still generating high energy savings outweigh most cons.
The discomfort glare can also be minimized if the LED street light has been designed to align to certain
guidelines as mentioned earlier. If the customer still appreciates or favors more the warm white light, we as
Beka Schreder can always offer such lighting system.
HEALTH EFFECTS OF LED LIGHTING |