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.