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Sustainability 2015, 7, 13454-13468; doi:10.3390/su71013454
sustainability
ISSN 2071-1050
www.mdpi.com/journal/sustainability
Article
Blue Light Hazard and Risk Group Classification of 8 W LED
Tubes, Replacing Fluorescent Tubes, through Optical
Radiation Measurements
Francesco Leccese 1,*, Viola Vandelanotte 2, Giacomo Salvadori 1 and Michele Rocca 1
1 LIghting and Acoustic Laboratory (LIA), Department of Energy engineering, Systems, Territory
and Construction (DESTeC), University of Pisa, Largo Lucio Lazzarino, 56122 Pisa, Italy;
E-Mails: giacomo.salvadori@ordineingegneripisa.it (G.S.); michele.rocca.au@gmail.com (M.R.)
2 Department of Energy Engineering, Faculty of Engineering Technology, KU Leuven, Technology
Campus-Ghent, 9000 Ghent, Belgium; E-Mail: viola.vandelanotte@hotmail.com
* Author to whom correspondence should be addressed; E-Mail: f.leccese@ing.unipi.it;
Tel.: +39-050-221-7158; Fax: +39-050-221-7150.
Academic Editor: Francesco Asdrubali
Received: 17 July 2015 / Accepted: 24 September 2015 / Published: 30 September 2015
Abstract: In this paper, the authors discuss the results of a measurement survey of
artificial optical radiation emitted by 8 W LED tubes suitable for the substitution of 18 W
fluorescent lamps used for general lighting. For both types of lamps, three different color
temperatures were chosen, 3000 K, 4000 K, and 6000 K. These measurements were
performed to evaluate the photobiological safety of the sources. The radiance and
irradiance values have been measured in a wide range of wavelengths (180–3000 nm). The
measurement results obtained for the LED tubes have been compared to those of similar
measurements obtained for fluorescent lamps. The analysis has been focused on the range
of wavelengths 300–700 nm, the blue light range, which turned out to be defining for the
risk groups of the lamps. This classification is a function of the maximum permissible
exposure time as indicated in the European Standard EN 62471 on the photobiological
safety of lamps and lamp systems.
Keywords: artificial optical radiation; LED tubes; fluorescent lamps; blue light hazard;
maximum permissible exposure time; risk group
OPEN ACCESS
Sustainability 2015, 7 13455
1. Introduction
Artificial optical radiation (AOR) is emitted by a very wide range of sources that people may be
exposed to, in the workplace and elsewhere. In order to guarantee sufficient safety minimizing the
artificial optical radiation hazard, different technical reports and guidelines have been issued by
international institutions [1–6].
AOR is separated into laser and non-coherent radiation in [5,6]. The non-coherent sources are
defined as all of the sources, apart from laser, that emit any radiation in the optical wavelength range
of 100 nm to 1 mm [5]. Among the non-coherent sources [1,6,7], special attention has been paid to
industrial process equipment (e.g., welding, paint drying ovens, melting of metal and glass, etc.) and
medical equipment (e.g., neonatal phototherapy lamps, sterilization, surgical lights, etc.), while minor
attention has been paid to non-coherent sources widely used in offices (e.g., lamps/luminaries, display
screen equipment, copiers, LED for lighting and signalization, etc.).
Nowadays the sources most used for the lighting of workplaces (particularly offices) are fluorescent
lamps [7–9]. With their efficacy, approaching that of fluorescent lamps, their long durability, small
size and low weight, LEDs are very often used to replace existing lamps [9–11]. These new
applications have placed increasingly stringent demands on the optical characterization of LEDs,
which serves as the fundamental baseline for product quality and product design [8,12–16].
In this paper, the authors discuss the results of a measurement survey of AOR emitted by 8 W LED
tubes suitable for substitution of 18 W tubular fluorescent lamps (length 60 cm), widely used for
general lighting of workplaces. The irradiance and radiance values, both measured and evaluated in a
wide range of wavelengths (from 180 nm to 3000 nm), have been analyzed in order to define the risk
group of LED as a function of the maximum permissible exposure time as indicated in the European
Standard EN 62471 [17] and in the Technical Report IEC 62778 [18]. By using the measurement
results, some consideration about blue light hazard (wavelengths 300–700 nm) has been made
regarding the prescriptions of the EU Directive 2006/25 [5] on the minimum health and safety
requirements for the exposure of workers to risks arising from AOR.
2. Risk Assessment for Human Exposure and Safety Assessment for the Lamps
2.1. Risk of Exposure to AOR
With reference to the risk of exposure, at the international level, it was considered necessary to
introduce measures protecting workers from the risks arising from AOR, on their health and safety, in
particular damage to the eyes and to the skin. In Table 1, the risks of exposure to AOR (for eyes and
skin) emitted by non-coherent sources are highlighted as a function of the wavelength [6].
With the EU Directive 2006/25 [5], the minimum requirements to protect workers against risks of
exposure to AOR have been specified. The content of the EU Directive 2006/25 has been fully taken
up by the Italian legislation, in particular: Legislative Decree 81/2008, Chapter V, Articles 213 to 218
and Annex XXXVII [19].
The limit values for the risk of exposure fixed by the Italian legislation [19], according to the EU
Directive [5], are shown in Table 2 for the different wavelength ranges between 180 and 3000 nm.
Sustainability 2015, 7 13456
Table 1. Risks of exposure to artificial optical radiation (AOR) emitted by non-coherent
sources as a function of the wavelength [6].
Wavelength
Range (nm) Hazard Bioeffect
180–400 Actinic UV skin and eye Eye: photokeratitis; conjunctivitis; cataractogenesis
Skin: erythema; elastosis
315–400 UVA eye Eye: cataractogenesis
Skin: -
300–700 Retinal blue light Eye: photoretinitis.
Skin: - Retinal blue light small source
380–1400 Retinal thermal Eye: retinal burn.
Skin: - 780–1400 Retinal thermal, weak visual stimulus
780–3000 Infrared radiation eye Eye: cornea burn; cataractogenesis.
Skin: -
380–3000 Thermal skin Eye: -
Skin: burn
Table 2. Limit values specified in the Italian legislation [19].
Risk Index Range Limit Value
(Legislative Decree 81/08)
Unit
Wavelength (nm) Name
(a) 180–400 UVA, UVB, UVC Heff = 30 J/m2
(b) 315–400 UVA HUVA = 104 J/m2
(c) 300–700 Blue Light LB = 106·t−1 W/m2sr
(d) Blue Light LB = 100 W/m2sr
(g)
380–1400
Visible, IRA LR = (2.8·107) Cα−1 W/m2sr
(h) Visible, IRA LR = (5·107) Cα−1·t−0.25 W/m2sr
(i) Visible, IRA LR = (8.89·108) Cα−1 W/m2sr
(j)
780–1400
IRA LR = (6·106) Cα−1 W/m2sr
(k) IRA LR = (5·107) Cα−1·t−0.75 W/m2sr
(l) IRA LR = (8.89·108) Cα−1 W/m2sr
(m) 780–3000 IRA, IRB EIR = 8000·t0.75 W/m2
(n) IRA, IRB EIR = 100 W/m2
(o) 380–3000 Visible, IRA, IRB Hskin = 20,000·t0.25 J/m2
Notes: The limit values for Indices (c) and (d) are referred to α ≥ 11 mrad. The coefficient Cα for Indices (g),
(h) and (i) can be evaluated as follow: Cα = 1.7 when α < 1.7 mrad; Cα = α when 1.7 ≤ α ≤ 100 mrad; Cα =
100 when α > 100 mrad. The coefficient Cα for Indices (j), (k) and (l) can be evaluated as follow: Cα = 11
when α < 11 mrad; Cα = α when 11 ≤ α ≤ 100 mrad; Cα = 100 when α > 100 mrad (if the visual field of the
measurements does not exceed 11 mrad). With the letters UVA, UVB, and UVC have been indicated the
ultraviolet radiation in the following ranges: 315–400 nm; 280–315 nm; 180–280 nm. With the letters IRA,
and IRB have been indicated the infrared radiation in the following ranges: 780–1400 nm (near-infrared);
1400–3000 nm (short-wavelength infrared).
Sustainability 2015, 7 13457
2.2. Photobiological Safety of the Emitting Lamps
Regarding the photobiological safety and quality of the marketed lamps, one of the more important
international standards is the EN 62471 “Photobiological safety of lamps and lamp systems”,
September 2008 [17].
According to EN 62471 [17], non-coherent sources of AOR are classified into risk groups as a
function of their potential photobiological hazard (see Table 3). If a source is assigned to a “safe”
group (Group 0) or to a low risk group (Group 1), there is no need for a detailed workplace evaluation,
since there is no photobiological safety hazard issue. It is necessary to observe that the evaluation of
the light sources separately may result in a different (higher) risk group classification than in the final
product. This classification takes place through an analysis, conducted on either the individual
components or the final product, and based on information obtained from the manufacturer.
It is important to point out that each group is defined as a function of the maximum permissible
exposure time [17]. Below this value, the lamp does not cause a photobiological risk for this specific
wavelength interval, as mentioned in Table 4.
Table 3. Description of risk groups [17].
Risk Group Description
Group 0 RG0 Exempt No photobiological hazard
Group 1 RG1 Low Risk No photobiological hazard under normal behavioral limitations
Group 2 RG2 Moderate Risk Does not pose a hazard due to aversion response to bright light or
thermal discomfort
Group 3 RG3 High Risk Hazardous even for momentary exposure
Table 4. Exposure time limits (in seconds) for risk group classification [17,20].
Hazard Exposure Time Limit (s)
RG0 RG1 RG2
Actinic UV 30,000 10,000 1000
UVA Hazard 1000 300 100
Blue Light Radiance 10,000 100 0.25
Retinal Blue Light, Small Source 10,000 100 0.25
Retinal Thermal 1000 100 10
IR Eye 1000 100 10
It is possible to determine the risk group of a source as follows: measure the spectral irradiance (or
radiance) at a specified distance for each hazard; weigh the measured values with appropriate
biological action spectra (indicated in the third column of Table 5); calculate the maximum permissible
exposure time (tmax) using the related equation shown in the fourth column of Table 5 (for example,
tmax for Actinic UV hazard can be calculated with the equation: tmax = 30/ES, where ES is the effective
ultraviolet irradiance); and determine the risk group by comparing tmax of the lamp with the exposure
time limit of each risk group (see Table 4).
It can be noticed that the risk groups are correlated with tmax, and tmax is correlated with the emission
of the lamps (irradiance or radiance). Therefore, it is possible to associate the risk group with the
Sustainability 2015, 7 13458
emission value and, thus, to determine the value of irradiance and radiance corresponding to each
exposure time limit [17,20].
According to [17], all of these different hazards (shown in Table 5) must be evaluated: at the
distance at which the illuminance reaches 500 lx (in the case of lamps for general lighting) and at the
distance of 0.20 m (in the case of all other lamps). It should be noticed that in the cases in which the
same lamps can be used both for general lighting and other applications, the evaluation should be
repeated in both configurations.
Regarding the blue light hazard, a specific technical report has been draw up [18]. This technical
report brings clarification and guidance concerning the assessment of blue light hazard of all lighting
products that have the main emission in the visible spectrum, specifically in the interval 300–700 nm,
similarly to [17], defining the risk group as shown in Table 6.
Table 5. Maximum permissible exposure time (tmax) of continuous wave lamps [17].
Hazard (Symbol) Quantity (Unit) Weighted Spectrum [6] tmax (s)
Actinic UV (ES) Irradiance 2
W
m
S(λ) 30/ES
UVA (EUVA) - 10,000/EUVA
Retinal Blue Light Radiance (LB) Radiance 2
W
msr
B(λ) 106/LB
Retinal Blue Light (small source) (EB) Irradiance 2
W
m
B(λ) 100/EB
Retinal Thermal (LR) Radiance 2
W
msr
R(λ)
()
4
B
50000/ Lα⋅
Retinal Thermal (weak visual stimulus) (LR) R(λ) -
IR (eye) (EIR) Irradiance 2
W
m
-
()
4/3
IR
18000/αE⋅
Notes: Small source defined as one with α < 0.011 rad. A visual stimulus can be considered weak if the
luminance of the source is lower than 10 cd/m2.
Table 6. Blue light hazard: correlation between tmax and risk group [18].
Risk Group RG0 RG1 RG2 RG3
tmax range (s) >10,000 100–10,000 0.25–100 <0.25
3. Description of the Analyzed Lamps
In this paper, a study was performed on commercially available LED tubes with a 60 cm length and
a diameter of 2.6 cm, with electric power of 8 W and color temperatures of 3000 K, 4000 K and
6000 K. These LED sources are adapted for the substitution of fluorescent lamps (commonly called
T8) with electric power of 18 W, an equal length and diameter and an analogue color temperature.
Such fluorescent lamps are widely used in the general lighting of workplaces [21,22] and, in particular,
in luminaires with four lamps (4 × 18 W), usually embedded in the ceiling and closed by a plastic
translucent screen or with an aluminum reflector to achieve a controlled luminance.
Each of the analyzed LED tubes is composed by a strip with 54 chip phosphor-based LED located
in the middle of the tube and an opal surface in the front that does not allow one to perceive the single
chip LED, but that produces a uniform light emission.
Sustainability 2015, 7 13459
The chosen lamps are a significant representation of the solutions available on the market for the
substitution of fluorescent lamps with LED tubes [16,20–23]. Regarding the substitution of fluorescent
lamps of 60 cm, nowadays, there are LED tubes available with electric power of 8 W up to 11 W. In
Table 7, the following properties, given by the manufacturer, for both of the LED tubes of 8 W and the
fluorescent lamps of 18 W are presented on the left: the length of the lamps (l), the power (P) the color
temperature (Tk), the luminous flux (Φ), the color rendering index (Ra) and the lifetime (D). On the
right part of Table 7, the spectra for the 4000 K lamps, measured at a distance of 0.20 m using a
spectrophotometer KONICA MINOLTA CL-500A [24], are represented as the relative distribution of
the measured radiance on the maximum radiance at the peak wavelength, for which the value is
also stated.
Table 7. Technical specifications of LED tubes and fluorescent lamps.
LED Tube Spectrum of 8 W LED Tube 4000 K
Peak at 448 nm: 52.4 mW/m2/nm
l 60 cm
P 8 W
T
k
3000 K, 4000 K, 6000 K
Φ 900 lm
Ra 80
D 40,000 h
Fluorescent lamp Spectrum of 18 W Fluorescent lamp 4000 K
Peak at 545 nm: 105.0 mW/m2/nm
l 60 cm
P 18 W
T
k
3000 K, 4000 K, 6000 K
Φ 1350 lm
Ra 80.89
D 20,000 h
4. AOR Measurements
The AOR measurements have been carried out at the Lighting and Acoustics Laboratory (LIA) of
the Department of Energy Engineering, Systems, Territory and Constructions (DESTeC) of the
University of Pisa. The measurements were performed on a sample of 96 lamps; in particular, 48 LED
tubes and 48 fluorescent lamps were analyzed, 16 for each color temperature (3000 K, 4000 K, and
6000 K) of both types.
Sustainability 2015, 7 13460
4.1. Measurement Instrument
The AOR measurements were realized using a Delta Ohm HD2402 broadband
photoradiometer [24], with six integrated sensors (Figure 1). The instrument used is a radiometer with
a spectral sensitivity in accordance to the specific weighting functions S(λ), B(λ) and R(λ).
Each of the six sensors measures in a specific wavelength interval between the ultraviolet (UV) and
infrared (IR) range. The sensors are the following: a radiometric sensor for UV (220–400 nm)
corrected with the spectral weighting factor S(λ); a radiometric sensor for UVA (315–400 nm); a
photometric sensor for the illumination in the visible range (380–780 nm); a radiometric sensor for the
blue light (400–700 nm) corrected with the spectral weighting factor B(λ); a radiometric sensor for IR
(700–1300 nm) corrected with the spectral weighting factor R(λ); a thermopile sensor to measure in
the visible, IRA and IRB range (400–2800 nm). The circular position of the sensors and the presence
of the integrated laser pointer, as demonstrated in Figure 1 [25], allow orientating the instrument
correctly toward the source. The radiometric parameter measured by the HD2402 instrument is always
irradiance (or illuminance as concerns Sensor 6 in Figure 1); however, the radiance and the irradiance
are related, and radiance can be obtained from irradiance (assuming that radiance is constant), provided that
the geometric parameters of the measured source are known [26,27].
This instrument is of practical use to obtain, with a single device, radiometric measurements of the
interesting parameters for each hazard as required by the EN 62471 [17] and indicated in Table 3.
1. Laser LED
2. Radiometric sensor for the measurements of the
UV range (220–440 nm)
3. Radiometric sensor for the measurements of the
UVA range (700–1300 nm)
4. Additional sensor
5. Radiometric sensor for the measurements of
UVA range (315–440 nm)
6. Radiometric sensor for the measurements of
visible radiation (lux meter)
7. Radiometric sensor of blue light range
(400–600 nm).
8. Predisposition for additional sensor
9. Thermopile sensor for the measurements of the
IRA-IRB range (400–2800 nm)
Figure 1. Delta Ohm HD2402 photoradiometer [25].
4.2. Conditions of the Measurements
The measurements have been carried out in the Lighting and Acoustic Laboratory of the University
of Pisa, where a suitable test chamber was realized, with the following dimensions: width 1.20 m,
length 2.00 m, height 2.10 m (Figure 2). This test chamber was constructed with a frame hanging from
Sustainability 2015, 7 13461
the ceiling on which a black fabric is fixed. The fabric is matt black (reflection factor 0.10) to create an
environment in which the contribution of the reflected light is negligible. The shades of the windows
of the room were completely shut to avoid the influence of the variability of daylight.
Each measurement had a duration of five minutes. Before measuring, the warm up time was
respected (5–15 min, depending on the source type), so the examined sources had time to reach their
regime state. The measurements have been performed at a distance of the source to detectors that
produces an illuminance of 500 lx, as indicated in EN 62471 [17] for lamps intended for general
lighting service (GLS). The measurements have been repeated at distances source to detectors equal to
0.2 m and 1.0 m in order to have a better characterization of the emission of each source [6,18].
4.3. Post-Processing Data
The post-processing of the irradiance measurements has been performed using the software
DeltaLog13 [25], provided together with the instrument. This software permits one to visualize in real
time the results of the measurements and to process the results saved on the instrument. With this
post-processing software, it is possible to obtain the necessary values for the illuminance, the
luminance, the irradiance and the radiance in the wavelength ranges of interest (see Table 1).
Figure 2. Test chamber: external view (left) and internal view (right).
As stated previously, the analysis of this study is focused particularly on the blue light range
(300–700 nm), as this range is the most significant in the case of lamps with phosphor-based LEDs.
These LEDs have generally a large emission in the interval of the Blue Light (as shown in the upper
part of Table 7), and therefore, an accurate evaluation of their emission is important, as in the
classification of the photobiological safety.
For the completeness of the study, the results of the measurements at the source to detector
distances of 0.2 m and 1.0 m are used to verify the risk of exposure according to what was
provided in [5,19].
Sustainability 2015, 7 13462
Concerning the verification of the risks of exposure for the workers, it is important to notice that it
is difficult to meet the conditions of an exposure analogue to those in the test (at a distance of 0.2 m
and 1.0 m with a viewing direction orthogonal to the source). These test conditions result in a more
severe situation than usual working activities. Consequently, obtaining a low risk of exposure in the
test conditions guarantees a low risk of exposure in the working conditions, except for particular and
infrequent cases (e.g., maintenance work on the devices with the light source on).
5. AOR Measurements Results
The following results of the AOR measurements have been divided in groups according to the type
of source (LED tube or fluorescent lamp) and color temperature (3000 K, 4000 K or 6000 K). For each
group and each distance, the limit value, the median and the standard deviation of the radiance are
represented in the blue light range (300–700 nm). Additionally, the obtained results are displayed for
every single LED tube of 4000 K.
5.1. LED Tubes
The results of the measurements of all of the 48 analyzed 8 W LED tubes (16 for each color
temperature) are shown in Table 8. In this table, the following values are indicated: the observation
distance, the angular dimension of the sources (α), the limit value (LBlim) of the radiance and the
median (M) and the standard deviation (SD) of the measured values.
In Table 9, the results of the AOR measurements of each of the sixteen 8 W LED tubes (named: S1,
S2, S3, ......, and S16) for the color temperature of 4000 K are shown in detail. For the evaluation of
the results, it must be observed that for the range 300–700 nm (blue light range), the limit value of the
radiance is 100 W/m2sr (see Section 2).
Table 8. Results of AOR measurements on 8 W LED tubes.
Distance (cm) Tk (K) α (mrad) LB (W/m2sr) 300–700 nm
LBlim M SD
20
3000 - - 83.31 4.70
4000 99.96 100 96.64 5.37
6000 - - 231.25 2.50
60 (500 lx)
3000 - - 19.62 0.86
4000 65 100 31.19 1.01
6000 - - 48.29 1.25
100
3000 - - 7.15 0.68
4000 60 100 15.20 0.39
6000 - - 19.87 0.83
Sustainability 2015, 7 13463
Table 9. Results of AOR measurements on 8 W LED tubes for 4000 K.
Distance (cm) Lamps LB (W/m2sr)
300–700 nm Lamps LB (W/m2sr)
300–700 nm Lamps LB (W/m2sr)
300–700 nm Lamps LB (W/m2sr)
300–700 nm
20
S1
85.64
S5
96.61
S9
112.2
S13
96.01
60 (500 lx) 31.61 30.01 31.20 32.61
100 11.27 11.98 12.53 12.25
20
S2
96.66
S6
84.84
S10
93.74
S14
96.54
60 (500 lx) 32.21 31.55 29.98 30.83
100 11.43 11.67 11.31 12.23
20
S3
98.35
S7
97.70
S11
97.03
S15
88.92
60 (500 lx) 29.77 30.17 32.01 31.12
100 12.28 12.14 11.75 11.66
20
S4
98.34
S8
100.5
S12
96.31
S16
98.72
60 (500 lx) 33.63 31.59 30.77 31.17
100 11.89 11.97 12.09 12.58
5.2. Fluorescent Lamps
The results of the measurements of all of the 48 analyzed 18 W fluorescent lamps (16 for each color
temperature) are shown in Table 10. In this table, similar to the LED tubes, are indicated: the
observation distance, the angular dimension of the sources (α), the limit value (LBlim) of the radiance
and the median (M) and the standard deviation (SD) of the measured values.
6. Discussion of the Measurements Results
The results of the measurements of the AOR are discussed below in relation to the photobiological
safety of the lamps with the resulting classification in risk groups. The discussion is completed with
the evaluation of the risk of exposure, according to the provided European and National legislation
(see Section 2).
Table 10. Results of AOR measurements on 18 W fluorescent lamps.
Distance (cm) Tk (K) α (mrad) LB (W/m2sr) 300–700 nm
LBlim M SD
20
3000 - - 35.00 0.78
4000 99.96 100 123.65 1.39
6000 - - 139.00 1.62
50 (500 lx)
3000 - - 15.59 1.06
4000 61.1 100 32.49 1.53
6000 - - 51.45 2.15
100
3000 - - 5.80 0.42
4000 60 100 9.75 0.59
6000 - - 14.70 0.99
It can be observed immediately that the distance at which the illuminance of the LED tubes reaches
500 lx is 0.60 m, and for the fluorescent lamps, this is 0.50 m. This can prompt questions, since the
Sustainability 2015, 7 13464
luminous flux of the LED tubes is 900 lm, and for the fluorescent lamps, it is 1350 lm. However, this
can be explained by the fact that the angle of the light beam of the LEDs is 120° and of the fluorescent
lamps 360°, and thus, the beam of the LED tubes is more concentrated.
6.1. Maximum Permissible Exposure Time and Risk Group Classification According to EN 62471
The risk group classification for the analyzed sources has been performed based on the radiance LB
(W/m2sr), which is the radiance emitted in the wavelength interval 300–700 nm (the blue light range).
In Table 11, the risk group (RG) and the tmax for each analyzed lamp are reported (calculated with the
median radiance value; see Tables 8 and 10). From these values, it can be noticed that the LED tube of
6000 K and fluorescent lamps of 4000 K and 6000 K are classified as RG1, with a tmax of 4324 s
(1 h 12 min), 8087 s (2 h 15 min) and 7194 s (2 h), respectively. The other lamps (LED tube 3000 K
and 4000 K, fluorescent lamp 3000 K) are classified as RG0. However, there are two lamps, S8 and S9
(see Table 12), in the group of LED tubes with a color temperature of 4000 K that have an LB value
higher than the limit of 100 W/m2sr and, thus, a tmax lower than 10,000 s (2 h 47 min): 9951 s (2 h
45 min) and 8909 s (2 h 28 min), respectively. Therefore, those two must be classified as RG1; see
also Table 12.
Table 11. Risk group classification of the analyzed lamps at a distance of 0.20 m.
Lamps LB (W/m2sr) tmax (s) RG
LED tubes 3000 K 83.31 >10,000 0
LED tubes 4000 K 96.64 >10,000 0
LED tubes 6000 K 231.25 4324 1
Fluorescent lamps 3000 K 35.00 >10,000 0
Fluorescent lamps 4000 K 123.65 8087 1
Fluorescent lamps 6000 K 139.00 7194 1
Table 12. Risk group classification and maximum permissible exposure time of the LED
tubes 4000 K at a distance of 0.20 m.
Lamps LB (W/m2sr) tmax (s) RG Lamps LB (W/m2sr) tmax (s) RG
S1 85.64 >10,000 0 S9 112.2 8909 1
S2 96.66 >10,000 0 S10 93.74 >10,000 0
S3 98.35 >10,000 0 S11 97.03 >10,000 0
S4 98.34 >10,000 0 S12 96.31 >10,000 0
S5 96.61 >10,000 0 S13 96.01 >10,000 0
S6 84.84 >10,000 0 S14 96.54 >10,000 0
S7 97.70 >10,000 0 S15 88.92 >10,000 0
S8 100.5 9951 1 S16 98.72 >10,000 0
6.2. Risk of Exposure to AOR According to Directive 2006/25/EC
From the results of the AOR measurements on the LED tubes shown in Table 8, it can be noticed
that the only LED tubes with a median radiance value higher than the limit value (LB = 100 W/m2sr)
are those with a color temperature of 6000 K, measured at a distance of 0.20 m. However, the values in
Sustainability 2015, 7 13465
Table 9 show that in the group of LED tubes of 4000 K, there are two lamps, S8 and S9, with a
radiance value higher than the limit: 100.5 W/m2sr and 112.2 W/m2sr, respectively. These results are
not perceptible only out of the median value.
The only fluorescent lamps with a median radiance value higher than the limit value
(LB = 100 W/m2sr) are those with a color temperature of 4000 K and 6000 K, measured at a distance
of 0.20 m.
In Figure 3, the median radiance values for LB, measured at a distance of 0.20 m, of all of the types
of lamps are set side by side. It is clear that the radiance values increase with the color temperature,
and at 4000 K, the radiance of both LED tubes and fluorescent lamps is near the limit value.
Figure 3. Comparison of the radiance LB in the blue light range between the LED tubes
(dark gray) and the fluorescent lamps (light gray) with different color temperatures at a
distance of 0.20 m.
7. Conclusions
In spite of the problem of the risk assessment from exposure to AOR having long been analyzed,
there are always new light sources available on the market, whose photobiological safety must be analyzed.
In this paper, the authors have shown and discussed the results of a measurement survey of AOR
emitted by 8 W LED tubes, which are suitable for the substitution of 18 W fluorescent lamps.
In a wide range of wavelengths (180–3000 nm), the irradiance values measured and the radiance
values calculated have been analyzed as required in the EU Directive 2006/25, and a risk group
according to the EN 62471 has been attributed to each LED tube.
From the measurement results, considering in particular the average values of the radiance, it is
possible to highlight that only the LED tubes with a color temperature of 6000 K are in Risk Group 1
(low risk); on the contrary, all of the other LED tubes are in Risk Group 0 (exempt risk). For the LED
tubes with a color temperature of 6000 K, the maximum permissible exposure time is however still
very high, approximately 4300 s.
Sustainability 2015, 7 13466
By comparison, the AOR emission analysis was also performed for the fluorescent lamps, which
could be replaced with the examined LED tubes. In this case, the fluorescent lamps of 4000 K and
6000 K are classified in Risk Group 1 (low risk) and the fluorescent lamps of 3000 K in Risk Group 0
(exempt risk). The fluorescent lamps of 4000 K and 6000 K have a maximum permissible exposure
times of 8100 s and 7200 s, respectively.
Although not generally harmful to health, the new LED sources, which are continuously inserted
into the market, require an accurate analysis of their emissions and a classification according to the risk
groups defined in the EN 62471 in order to make both installers and users aware of the safe manners of
exposition and about the maximum permissible exposure times to these sources.
Acknowledgments
The Authors want to thank the Technical Staff of the Department of Energy engineering, Systems,
Territory and Construction (DESTeC) of the University of Pisa, in particular: Mr. Massimo Ciampalini
and Mr. Roberto Manetti for their cooperation during the measurements activity.
Author Contributions
These authors contributed equally to this work.
Conflicts of Interest
The authors declare no conflicts of interest.
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