Environmental Engineering Reference
In-Depth Information
ANNEX 1 - Applying the Ultraviolet Radiation Exposure Limits
The ACGIH/ICNIRP EL for exposure to the eye and skin to UVR is 3 mJ/cm
2
-effective, when the
spectral irradiance E
Ȝ
at the eye or skin surface is mathematically weighted against the hazard sensitivity
spectrum S(Ȝ) from 180 nm to 400 nm as follows:
E
eff
= EȜǜS(Ȝ)ǜǻȜ
(1)
The permissible exposure duration, t
max
, in seconds, to the spectrally weighted UVR is calculated by:
t
max
= (3 mJ/cm
2
) / E
eff
(W/cm
2
)
(2)
In addition to the above requirement, the ocular exposure is also limited to 1 J/cm
2
for periods up to
1000 s (16.7 min) by ACGIH and to 30,000 s by ICNIRP. ACGIH limits the total irradiance to 1 mW/cm
2
for
periods greater than 1,000 s. For this requirement, the total irradiance, E
uva
, in the UV-A spectral region is
summed from 315 nm to 400 nm:
400
¦
E
UVA
E
'
O
(3)
O
315
where E
Ȝ
is the spectral irradiance in W/(cm
2
-nm).
One way to express the ACGIH limit for the UV-A is: if the total irradiance exceeds the 8-hour
criterion of 1 mW/cm
2
, the maximum exposure must also be less than:
t
max
= (1 J/cm
2
) / E
UVA
(W/cm
2
)
(4)
Equation (4) applies to all periods up to 8 h for the ICNIRP guidelines.
Table A1.1 UVR Hazard Spectral Weighting Function.
Wavelength
(nm)
UVR Hazard
Function S
UV
(Ȝ)
Wavelength
(nm)
UVR Hazard
Function S
UV
(Ȝ)
Wavelength
(nm)
UVR Hazard
Function S
UV
(Ȝ)
180
0.012
260
0.650
335
0.00034
190
0.019
265
0.810
340
0.00028
200
0.030
270
1.000
345
0.00024
205
0.051
275
0.960
350
0.00020
210
0.075
280
0.880
355
0.00016
215
0.095
285
0.770
360
0.00013
220
0.012
290
0.640
365
0.00011
225
0.015
295
0.540
370
0.000093
230
0.019
300
0.300
375
0.000077
235
0.240
305
0.060
380
0.000064
240
0.300
310
0.014
385
0.000053
245
0.360
315
0.003
390
0.000044
250
0.430
320
0.001
395
0.000036
*254
0.500
325
0.0005
400
0.000030
255
0.520
330
0.00041
*Low-pressure mercury germicidal lamp emission.
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