Specifying LEDS: Rewards & RisksThe effect of artificial Light on Circadian

Rythmicity

Alan Grant, Design and Development Director

DW Windsor

The revolution

The media

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”

“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”

Scientific Committee on Health, Environmental and Emerging Risks

SCHEER

Potential risks to human health of Light Emitting Diodes (July 2017)

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.”

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

19 October 2017 Footer title

Concerns

should not

be ignored

SCHEERPotential 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.”

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…..”

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

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

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

●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

eye

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

●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

CCT examples

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

Circadian Rhythm

● Biological timekeeping system imposes

day/night rhythm:

● Behavior (sleep/wake cycle), body

temperature, hormone control, immune

response, energy metabolism

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)

Circadian Rhythm

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)

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)

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

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

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

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)

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

Light Source Melanopic Content

Pacific North West National Laboratory

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

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.

SCHEERPotential 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.”

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

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

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

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

Keep in touch:

DW Windsor

Pindar Road, Hoddesdon,

Hertfordshire, EN11 0DX

+44(0)1992 474600

dwwindsor.com

Thank you