This document discusses the potential health risks of LED lighting, particularly from exposure to blue light at night. It summarizes research finding links between light at night and increased risks of breast cancer, diabetes, and sleep disorders. Studies suggest that blue light can disrupt circadian rhythms by suppressing melatonin production. While direct health effects of LEDs are unclear, late-evening exposure to light may impact circadian rhythms. Variables like light spectrum, intensity, duration and timing of exposure are important. High color temperature white LEDs contain more short wavelengths of blue light, which can be detrimental to health. Younger and older individuals may be more susceptible to circadian disruption from light at night.

1. Specifying LEDS:
Rewards & Risks
The effect of artificial Light on Circadian
Rythmicity
Alan Grant, Design and Development Director
DW Windsor

2. The revolution

3. The media

4. Concerns from Professional
bodiesChronobiology International
“Human exposure to artificial light at night is associated
with an increased risk of several health problems,
including breast cancer, diabetes and sleeping disorders”
Journal of Molecular Psychiatry
“Link between exposure to night-time light and mental
health”
Department of Environmental Health, Harvard
School of Public Health
“study strengthens link between breast cancer and
outdoor light exposure at night”

5. “Use lower CCT lights (than
4000K) that will minimize
potential health and
environmental effects”
“Consideration should be given
to reducing the CCT (below
4000K); avoiding potential
adverse effects on melatonin
production in the evening”

6. Scientific Committee on Health, Environmental
and Emerging Risks
SCHEER
Potential risks to human health of Light
Emitting Diodes (July 2017)

7. Economic and ecological
agreement
“…our American Medical Association (AMA)
support the proper conversion to community-
based Light Emitting Diode (LED) lighting, which
reduces energy consumption and decreases the
use of fossil fuels.”

8. Benefits of LEDs
● Strong economic argument
● Significant energy savings
● Long life
● Very little (no) maintenance through life
● Dimming & Control
● Excellent colour rendering
● Reduction in energy generation
● Improvement in air quality

9. 19 October 2017 Footer title
Concerns
should not
be ignored

10. SCHEER
Potential Risks to Human Health of LEDs
“The Committee concluded that there is no
evidence of direct adverse health effects from
LEDs emission in normal use (lamps and displays)
by the general healthy population.”
“There is a low level of evidence that exposure to
light in the late evening, including that from LED
lighting and/or screens may have an impact on
the circadian rhythm. At the moment, it is not yet
clear if this disturbance of the circadian system
leads to adverse health effects.”

11. SCHEER
Potential Risks to Human Health of LEDs
“Many people perceive white colour 4000K LED
lighting as harsh because almost 30% of the
spectrum is emitted as blue light”
“Short-wavelength light (peak around 480nm)
influences the circadian system…..”

12. SCHEER
Potential Risks to Human Health of LEDs
“There are several variables to be taken into
account when referring to the effects of optical
radiation from LEDs on human health:
1) Spectrum of a LED light source
2) Intensity of the lighting…in the blue part of
spectrum
3) Duration of exposure
4) Exposure level at the eye or skin
5) Health of the eye or skin
6) Direct staring without deviation v eye movement

13. Context
“…that exposure to light in the late evening,
including that from LED lighting and/or screens
may have an impact on the circadian rhythm.”
• Spectum of the LED source
• Circadian Rhythmicity
• Age related risk

14. CCT Concern
● High CCT white light sources have a relatively
greater short-wavelength content compared to
HPS lamps
● Increased presence of short wavelengths in
the night environment may be detrimental to
health

15. ●Measure of the blueness of a
light source (CIE 2011)
●Used for categorizing
appearance & works really well
for lamps – which are a fixed
colour
●When combined, the
combination of the range of
wavelengths produce the colour
of light perceived by the human

16. Spectral Power Distribution
The SPD of a light source is the amount of
radiant power it emits at different wavelengths
across the visible spectrum and is the
fundamental light-source information used in
colour science

17. ●Light sources with different SPDs
can have the same CCT
●Light sources with the same CCT
can look different
●CCT is only a rough guide of the
actual spectral content of a light
source

18. CCT examples

20. Circadian Rhythm
● Circadian: “approximately one day” (Andersen 2012)
● Ambient light levels are the main information
our bodies use to synchronise themselves
(Andersen 2012)
● The presence of a light (day) and dark (night)
phase due to the earth’s rotation has resulted
in the evolution of an internal clock in almost
all organisms, including humans

21. Circadian Rhythm
● Biological timekeeping system imposes
day/night rhythm:
● Behavior (sleep/wake cycle), body
temperature, hormone control, immune
response, energy metabolism

22. Impairment of Circadian Rhythm
● Chronic impairment of the circadian system
has been shown to compromise health
● Disruption of CR in shift workers:
● Sleep and cognitive impairment
● Psychiatric disorders
● Gastrointestinal issues
● Breast cancer
(Knutsson 2003, Kecklund & Alexsson 2016)

23. Circadian Rhythm

24. Circadian Rhythm
Exposure to light in the late evening or night
can have an immediate alerting effect,
suppress the secretion of the hormone
melatonin, delay the timing and reduce the
function of the circadian system
(PHE 2016)

25. Circadian Rhythm
The severity of the effect (of light at night)
depends on the dose and timing – how much, for
how long, the spectral power distribution and
whether the exposure occurs early, in the middle
or late during the night time
(PHE 2016, Chang 2015, Chellappa 2013)

26. Circadian Rhythm
● How much?
● <100 lux
● For how long?
● Seconds to minutes (Glickman, Levin et al)
● Exposure Timing?
● Early: delay CR
● Middle: Significant disturbance
● Late: advance CR

27. Visual System Stimulation
● Mammals receive light information through the
eyes which perform two major functions
● Image forming
● Non-image forming adaption of physiology and
behavior to light
● Different wavelengths of light appear to have
different effects on the biological clock
● Spectral sensitivity of the photoreceptors in
the retina

28. Visual System Stimulation
● 5 types of Photoreceptors in the human eye
● 3 different Cone receptors: responsible for
colour & detailed vision in photopic (well lit)
conditions
● Different cone receptors for : short, medium,
long wavelength light
● Rod receptors provide monochromatic vision
in scotopic (low light) conditions
● Recently discovered : Intrinsically
Photosensitive Retinal Ganglion Cells (ipRGC)
which crucially relay light information to parts
of the brain controlling the biological clock

29. Non-Visual System Stimulation
● ipRGCs relevant to circadian physiology, pupil
dilation & other non-visual effects
● ipRGCs contain melanopsin, a photopigment
with a peak sensitivity of 480-490nm (Lucas 2014)
● This peak is at the upper end of the range of
wavelengths commonly described as blue
● ipRGCs are the primary conduits through
which photic information passes to NIF
centres of the brain: SCN of the hypothalamus
● The ipRGCs directly affect the parts of the
brain outside the visual cortex (Berson 2002)

30. Light Source Melanopic Content
● All light at night can potentially contribute to
biological responses & health concerns
● White light with high proportion of short
wavelengths characterised as higher
melanopic content
● Reducing total luminous flux from a light
source reduces the melanopic content by the
same amount

31. Light Source Melanopic Content
Pacific North West National Laboratory

32. Age Related Risk
● The transmission of blue light to the retina
is higher in younger children than in older
children (above about three years) and
adults (ICNIRP 2013)
● Elderly people have less robust circadian
systems (Cornelissen and Otsuka 2016) and may be
more susceptible to circadian disturbance
caused by artificial light
● The aging eye transmits less blue light to
the retina and is more susceptible to
scatter light at these wavelengths

33. Ocular safety
● LED street lights (tested by PHE) were
not bright enough to cause retinal
damage in normal use at reasonable
distances
● At 2m viewing distance to reach
exposure limits for Blue Light Hazard
would require steady fixation for over 2
½ hours (PHE 2016)
● Consideration for installations close to
windows etc.

34. SCHEER
Potential Risks to Human Health of LEDs
“The Committee concluded that there is no
evidence of direct adverse health effects from
LEDs emission in normal use (lamps and displays)
by the general healthy population.”
“There is a low level of evidence that exposure to
light in the late evening, including that from LED
lighting and/or screens may have an impact on
the circadian rhythm. At the moment, it is not yet
clear if this disturbance of the circadian system
leads to adverse health effects.”

35. SCHEER
Potential Risks to Human Health of LEDs
“There are several variables to be taken into
account when referring to the effects of optical
radiation from LEDs on human health:
1) Spectrum of a LED light source
2) Intensity of the lighting…in the blue part of
spectrum
3) Duration of exposure
4) Exposure level at the eye or skin
5) Health of the eye or skin
6) Direct staring without deviation v eye movement

36. Perspective
● LED Lighting is, in general, fantastic
● There is some concern about LEDs :
• Glare
• Colour of white light
• Obtrusive light
• Long term effects on health
● Poor installations
● Huge choice of CCT & flux binning
● Trade-off between colour and luminous flux
● Energy is a key driver

37. Working together
• Manufacturers, designers, specifiers and
installers - all have a part to play
• Good optical control, good cut-off, suitable
shielding
• Not using a one-size-fits-all solution
• Accurate and appropriate information
• Colour temperature options

38. The future is bright …
• LEDs: long lasting, reliable energy efficient solution
• Public & professional concern about light & its
potential to disrupt sleep patterns & cause illness
(directly or indirectly)
• Lighting technology is moving too fast for neuro-
science, photobiology or lighting standards to keep
up
• The industry needs to take note of concerns &
mitigate risks
just slightly less
blue

39. Keep in touch:
DW Windsor
Pindar Road, Hoddesdon,
Hertfordshire, EN11 0DX
+44(0)1992 474600
dwwindsor.com
Thank you