Selected Blue Light Characteristics of Various Outdoor Lighting Sources at Equivalent Lumen Output

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Table 1 below lists various sources used in street and area lighting (among other applications) along with selected characteristics related to their spectral content, normalized for equivalent lumen output. The table was updated in June 2017 from an earlier version to increase the number of LED samples on which the corresponding data ranges are based (see Table 2). Data for each source includes a measured correlated color temperature (CCT), the calculated percentage of radiant power contained in "blue wavelengths" (defined here from the literature related to sky glow as wavelengths between 405 and 530 nanometers [nm]), and the corresponding scotopic and melanopic multipliers that are shown relative to a high-pressure sodium (HPS) baseline due to its predominance in the existing outdoor lighting market.

Table 1: Selected blue light characteristics of various outdoor lighting sources at equivalent lumen output.

Row

Light source

Luminous Flux (lm)

CCT (K)

% Blue*

Relative Scotopic Potential

Relative Melanopic Potential**

A

PC White LED

1000

2700

15% - 21%

1.74 - 2.33

1.90 - 2.82

B

PC White LED

1000

3000

18% - 25%

1.88 - 2.46

2.09 - 3.06

C

PC White LED

1000

3500

22% - 28%

2.04 - 2.54

2.34 - 3.25

D

PC White LED

1000

4000

26% - 33%

2.11 - 2.77

2.36 - 3.64

E

PC White LED

1000

4500

32% - 35%

2.39 - 2.94

2.83 - 3.95

F

PC White LED

1000

5000

35% - 40%

2.61 - 3.43

3.22 - 4.69

G

PC White LED

1000

5700

39% - 45%

2.75 - 3.39

3.42 - 4.62

H

PC White LED

1000

6500

43% - 48%

3.12 - 3.97

4.10 - 5.87

I

Narrowband Amber LED

1000

1606

0%

0.36

0.12

J

Low Pressure Sodium

1000

1718

0%

0.34

0.10

K

PC Amber LED

1000

1872

1%

0.70

0.42

L

High Pressure Sodium

1000

1959

9%

0.89

0.86

M

High Pressure Sodium

1000

2041

10%

1.00

1.00

N

Mercury Vapor

1000

6924

36%

2.33

2.47

O

Mercury Vapor

1000

4037

35%

2.13

2.51

P

Metal Halide

1000

3145

24%

2.16

2.56

Q

Metal Halide

1000

4002

33%

2.53

3.16

R

Metal Halide

1000

4041

35%

2.84

3.75

S

Moonlight†

1000

4681

29%

3.33

4.56

T

Incandescent

1000

2812

11%

2.21

2.72

U

Halogen

1000

2934

13%

2.28

2.81

V

F32T8/830 Fluorescent

1000

2940

20%

2.02

2.29

W

F32T8/835 Fluorescent

1000

3480

26%

2.37

2.87

X

F32T8/841 Fluorescent

1000

3969

30%

2.58

3.18

* Percent blue calculated according to LSPDD: Light Spectral Power Distribution Database, http://galileo.graphycs.cegepsherbrooke.qc.CA/app/en/home.

** Melanopic content calculated according to CIE Irradiance Toolbox, http://files.cie.co.at/784_TN003_Toolbox.xls (download), 2015.

† Moonlight CCT provided by Telelumen, LLC.

The ranges listed for the LED properties reflect the fact that various products often differ from one another in terms of their precise spectral content, even when binned together in the same nominal CCT, and each CCT bin listed in the table contains numerous product samples. The exact number of samples in each bin ranges from 20 (for 5700 K) to 162 (for 3000 K), with others falling in between (457 samples in all; see Table 2). Conventional light sources are all represented by single values though they would likewise be more accurately characterized by a range (albeit much narrower than LED). 

Table 2: Number of LED products underlying the data ranges shown for each CCT bin in Table 1.

Count

Row

Light source

Luminous Flux (lm)

CCT (K)

59

A

PC White LED

1000

2700

162

B

PC White LED

1000

3000

53

C

PC White LED

1000

3500

51

D

PC White LED

1000

4000

36

E

PC White LED

1000

4500

44

F

PC White LED

1000

5000

20

G

PC White LED

1000

5700

32

H

PC White LED

1000

6500

Most importantly, performing a calculation with these values only provides an idea of the relative potential to cause health or other impacts, rather than detailing any actual impacts likely to occur. Impacts are critically related to additional factors such as intensity, length of exposure, and other exogenous variables that are not represented in the table.

Nevertheless, the potential influence of blue wavelengths is immediately evident in all "white light" sources containing them. In addition, as demonstrated by the relative properties displayed by conventional lighting sources in the table, the blue light issues that have been raised in recent debate are clearly nothing new to our lighted environment. What is new is our increased understanding of their potential influence regarding human and environmental health issues, as the related research has evolved. Much work remains to put any associated potential risk into a realistic context, however.