Patty's Industrial Hygiene, Physical and Biological Agents. Группа авторов

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      for t less than 10 seconds, where H_skin, the unweighted radiant exposure at the skin, is expressed in J cm⁻². The sensation of pain is expected to cause avoidance of exposures longer than 10 seconds.

      4.1.5 Numerical Values of Spectral Weighting Functions

      Numerical values of S(λ), B(λ), A(λ), and R(λ) are available in tabular form in numerous publications 15, 16, 19–21.

Numerical values of the CIE erythema reference action spectrum can be computed using the following formulas (17):

      (19)

      for λ between 250 and 298 nm;

      (20)

      for λ between 298 and 328 nm; and

      (21)

      for λ between 328 and 400 nm.

      4.1.6 Ozone Hazard from UV‐C Sources

      UV radiation of wavelength shorter than 242 nm interacts photochemically with O₂ to form ozone, a highly irritating and potentially lethal gas. Potential sources of ozone‐generating UV radiation include gas shielded arc welding, xenon lamps, mercury lamps (including some germicidal lamps), excimer lamps, and deuterium lamps. Ozone exposure should be controlled by means of local exhaust ventilation at the source.

      4.2 Measurement of Optical Radiation

      To measure broadband optical radiation in a way that is meaningful for assessing health hazards, it is necessary to take account of the spectral distribution of the radiation and apply an appropriate spectral weighting function. This can be done by either (i) using a spectroradiometer, which measures the amount of incident radiation in narrow wavelength bands, then mathematically weighting the measured spectral distribution using the relevant hazard function or (ii) using a broadband radiometer with a detector that has a spectral response function that closely matches the relevant hazard function.

      For accurate irradiance or radiant exposure measurements, the input optics of the measurement instrument should have a directional response that is proportional to the cosine of the angle between the normal to the receiving surface and the line of sight from the receiving surface to the radiation source (22, 23).

      4.2.1 Spectroradiometers

      Double‐monochromator spectroradiometers are considered the “gold standard” for measurement of the spectral distribution of optical radiation. Unfortunately, double‐monochromator spectroradiometers are not suited to field industrial hygiene measurements because of their large size, delicate components, and time necessary to scan through the entire spectral range of interest in narrow bandwidth steps. Single‐monochromator diode array spectroradiometers (SMDASs) are portable and relatively inexpensive instruments that can measure radiation in multiple narrow bandwidths simultaneously. Performance criteria have been established for SMDASs for the measurement of solar UV (22). Numerical corrections for stray light may be applied to reduce spectral measurement error (24, 25), but in some cases, such corrections may yield anomalous results on the UV region (25, 26). Corrected SMDASs should be validated against double‐monochromator spectroradiometers using sources that are representative of those in the workplace (24).

      4.2.2 Broadband Detectors and Dosimeters

Portable, easy‐to‐use broadband detectors for optical radiation are widely available. Electronic broadband detectors for UV, visible, and IR‐A radiation typically use a semiconductor photodiode that produces a current proportional to the photon flux at a given wavelength. The spectral responsivity of a photodiode may be defined as the ratio of current generated to radiant power incident on the detector. Based on Eqs. (1) and (2), the incident power is proportional to the photon flux and inversely proportional to the wavelength. The spectral responsivity also depends on the inherent quantum efficiency of the device, which is a function of λ, and on the spectral transmittance of any filters and input optics. Some UV detectors include a phosphor that absorbs UV and emits visible photons that are detected by the photodiode.

      Detectors are commercially available with relative spectral responses that approximate the ACGIH relative spectral effectiveness function S(λ) for UV, the CIE erythema reference action spectrum S_er(λ), the ACGIH blue‐light hazard function B(λ), and the ACGIH retinal thermal hazard function R(λ). Photometers, which are used to measure illumination levels, have a spectral response matched to the photopic luminous efficiency function. Unweighted IR irradiance may be measured using thermopile or pyroelectric detectors, which give a nearly uniform response over a wide spectral range.

      Performance characteristics for broadband UV radiometers have been described by the World Meteorological Organization for measurement of solar erythemal radiation (23) and by the CIE 220:2016 guideline for measurement of artificial sources (27). Radiometers with broadband detectors are typically calibrated to read out directly in irradiance units such as W m⁻². Integrating radiometers can be set to measure radiant exposure received over time. An evaluation of the directional response of broadband UV detectors from seven different manufacturers with four different main types of input optic found that raised polytetrafluoroethylene (PTFE) dome diffusers showed the best directional response compared to recessed PTFE diffusers, quartz diffusers, or no diffuser (28). The raised PTFE diffusers had directional errors of 4–10% relative to an ideal cosine response. Modeling suggests that optimized raised planar diffusers and dome diffusers can have directional errors less than 2% (29), and some commercially available diffusers are reported to have directional error in this range. UV sources that subtend an angle greater than 80° need only be measured over a field of view of 80° (15). For assessments of retinal hazards, measurements of source radiance should be made using a detector equipped with input optics that narrow the field of view to 0.011 rad (30).

      Personal UV dosimetry methods used in research on occupational or community UV exposure include small electronic dosimeters, UV‐sensitive chemical films such as polysulphone (34) and poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) (35), and UV‐sensitive biofilms (36, 37). A wearable sensor patch has recently been developed that uses UV‐induced color change in a dye, which is read using a smartphone app, to measure personal erythemal dose (38). Electronic personal dosimeters or dataloggers with spectral response approximating the CIE erythemal or ACGIH/ICNIRP UV‐hazard functions are commercially available.

      4.2.2.1 Spectral Corrections for Broadband Detectors

      Significant errors in measurement of effective irradiance or dose can result when the spectral response of a broadband detector is not well matched to the spectral weighting function for the biological effect of interest. Under these circumstances, a broadband detector that is calibrated using a monochromatic calibration source will give inaccurate readings when measuring broadband radiation. The deviation of the broadband detector reading from the true effective irradiance СКАЧАТЬ