1Centre for Astronomy and Atmospheric Research, University of Southern Queensland, Toowoomba, 4350, Australia. Ph: 61 7 46 312226. Fax: 61 7 46 312721. Email: email@example.com
2Centre for Medical and Health Physics, School of Physical Sciences, Queensland University of Technology, GPO Box 2434, Brisbane, 4001, Australia.
(*To whom correspondence should be addressed)
The ranges of conditions and environments of a dosimetric spectrum evaluator previously developed and employed in the evaluation of the UV source spectrum have been considered in this paper. The complete system of four dosimeter materials can be employed for a total UV exposure of up to approximately 10 J cm-2. The exposure times required were influenced by the UV environment. The exposure times ranged from 20 minutes to 3 hours for filtered solar erythemal UV, 5 to 30 minutes for solar erythemal UV, 30 to 53 minutes for quartz tungsten halogen lamp erythemal UV, 10 to 15 minutes for plant damage solar UV and 90 minutes for plant damage UV from fluorescent sun lamps. In these environments, employing the system in open and well-ventilated conditions minimises changes in the dose response of the system due to temperature. The results in this paper provide a guide for the range of conditions and exposure times required for different environments for future research employing the dosimetric spectrum evaluator.
Ultraviolet (UV) radiation is a genotoxic and has a causative role in human skin cancer, premature skin photo-aging and wrinkling and some eye disorders (Longstreth et al., 1995). Additionally, increased ultraviolet irradiances due to stratospheric ozone depletion may affect plant growth (Caldwell et al., 1995). An improved characterisation and understanding through UV measurements of the solar UV exposures to humans and plants is required.
The measurement of UV radiation in photobiological experiments has been
reviewed in another paper (Wong and Parisi, 1998). Spectroradiometers and
radiometers may be employed for ambient UV measurements on a horizontal
plane. However, UV dosimeters must be employed for simultaneous multi-site
measurements of the UV irradiances to specific sites on the object of study.
Dosimeters based on polysulphone (Diffey, 1989) and CR-39 (Wong et al.,
1992) have been employed for erythemal UV measurements. A dosimetric spectrum
evaluator based on four different UV dosimeter materials has been developed
(Parisi et al., 1997, Parisi and Wong, 1996a) and employed in photobiological
research (for example, Parisi et al., 1998a). Each of the materials is
sensitive to different UV wavelengths and measurement of the change in
the optical absorbance of each of the materials at a set wavelength for
each material allows broad scale evaluation of the UV spectrum. The minimum
irradiance required on this type of detector is 0.01 mW
cm-2. This paper investigates the range of conditions and exposure
times of the spectrum evaluator system for different UV environments.
The biologically effective UV irradiance (UVBE) has been calculated as follows:
UVBE = ò uv Sl Al dl (1)
where Sl is the source UV spectrum and Al is the action spectrum for the biological process. In this paper, the action spectrum for human erythema (CIE, 1987) and the generalised plant damage action spectrum (Caldwell, 1971) are employed.
Table 3 The range of biologically effective irradiances for erythema(a)
and plant damage(b) and the approximate exposure times that
may be employed.
CONCLUSION AND DISCUSSION
The ranges of conditions and environments of a dosimetric spectrum evaluator previously developed and employed in the evaluation of the UV source spectrum have been considered in this paper. The complete system of four dosimeter materials can be employed for a total UV exposure of up to approximately 10 J cm-2. For the different environments, the exposure times required for the spectrum evaluator were found to be a compromise between producing a measurable change in optical absorbance of the dosimeter material and reducing the saturation of the dosimeter material and minimising any changes in the source spectrum. The exposure times ranged from 5 minutes to 3 hours and were dependent on the UV irradiances and the general shape of the UV spectrum, which was influenced by the UV environment. In these environments, employing the system in open or well-ventilated conditions up to temperatures of 50 oC minimises changes in the dose response of the system due to temperature. The results presented in this paper provide a guide for the ranges of conditions and exposure times required for the different environments for future research employing the dosimetric spectrum evaluator.
Acknowledgments The authors would like to thank Ken Mottram, Ron Matthews, Oliver Kinder, Graeme Holmes and Dennis Cracknell in the USQ physics discipline whose technical expertise contributed to these projects.
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