Personal UV Dosimeters

NIWA has collaborated in the development of personal UV dosimeter badges to support studies relating UV exposure to human health.

There is widespread public interest in the relationships between UV radiation and health. The effects of UV on health can be harmful – as in its effect on skin cancer rates, or beneficial – as in the case of its effect on vitamin D status. In the past, researchers have attempted to determine these relationships as functions of ambient UV radiation. However, the UV doses that humans typically receive are less than 5% of the available UV [1, 2].

To address that limitation, personal UV dosimeter badges have been developed to support studies relating UV exposure to human health. The badges were designed by Dr Martin Allen (Dept of Electrical and Computer Engineering, University of Canterbury), and have already been used successfully in several studies involving skiers, outdoor workers, school children, and a large HRC-sponsored study involving NIWA and the Universities of Auckland and Otago to relate personal UV exposure and vitamin D status among New Zealanders [2-6]. The performance of the badges relative to standard instrumentation has also been assessed [7].

The badges are conveniently small and lightweight. They look similar to wrist watches, except that there is no real time display. This is deliberate, because the aim of the devices would be thwarted if the users’ behaviour was modified while wearing them. The badges are robust and water resistant (they have been known to survive a washing machine treatment). They were originally designed to be pinned to the lapel, but they can also be attached to straps suitable for wearing as wrist watches, or arm bands.

The foreoptic comprises a diffuser that is machined from PTFE so that the angular response is similar to the cosine weighting required for irradiance measurements. The radiation sensor is an AlGaN photodiode with a spectral response function that is similar to the action spectrum for inducing erythema (sunburn) in humans. The sampling interval is programmable with a range from 4 seconds to hours. The badge is powered by a standard lithium 3V coin cell, which has a life of up to 20 weeks. The UV measurement is amplified and digitised, and stored in the on-board memory (1 Mbit EEPROM) which is sufficient for several weeks’ continuous operation. The software includes data compression when UV levels are low, and user-programmable ‘on – off’ times to avoid data logging at night or outside study periods.

The badge logging parameters are specified with a purpose-developed computer program that runs under MS Windows operating systems. Data transfer is via standard USB ports using a supplied connecting cable or, in a different version, through a cradle with wireless connection to the badge. The same program is used to upload data from the badge for further analysis.

Each badge has a unique identifying label. Calibration parameters to convert badge counts to erythemally-weighted UV (or UV Index) can be provided via a cross calibration procedure developed at NIWA. Application of this procedure provides a calibration traceable to the NIST irradiance scale via research-grade monitoring instruments which are in turn calibrated against state-of-the-art UV spectrometer systems located at Lauder. These calibration factors can be applied by the users, or NIWA can convert raw data files.

NIWA maintains a set of dosimeter badges for its own study purposes. Sets of badges can also be purchased (contacts: [email protected] or [email protected]).

Future improvements currently under development include:

• increased data storage capacity (x 10)
• lower power consumption to increase battery life.

Important Notice

These devices are currently being used in research projects in New Zealand. If they are lost, valuable data is also lost. So if you happen to find one of them, please contact NIWA UVB Enquiries as soon as possible, details below, or phone: 03 4400430.

Thank you very much.

References

1. Knuschke, P., et al., Personenbezogene messung der UV-Exposition von Arbeitnehmern im freien. 2007, Bundesanstalt fur Arbeitsschutz und Arbeitsmedian (BAUA): Dortmund/Berlin/Dresden. p. 195.

2. Wright, C.Y., et al., Solar UVR exposure, concurrent activities and sun-protective practices among primary schoolchildren. Photochemistry and Photobiology, 2007. 83: p. 749-758.

3. Allen, M. and R. McKenzie, Enhanced UV exposure on a ski-field compared with exposures at sea level. Photochemical & Photobiological Sciences, 2005. 4(5): p. 429-437.

4. Wright, C., G. Bodeker, and A. Reeder, UV radiation exposure in New Zealand school children. Water & Atmosphere, 2005. 13(2): p. 1-11.

5. Allen, M. and R.L. McKenzie. UV exposure on New Zealand ski-fields. in UV Radiation and its Effects: an update 2006. 2006. Wellington: Royal Society of New Zealand, Miscellaneous Series, No. 68.

6. McKenzie, R., Liley, B., Johnston, P., Scragg, R., Stewart, A., Reeder, A., Allen, M. (2013) Small doses from artificial UV sources elucidate the photo-production of Vitamin D. Photochemical & Photobiological Sciences, 12: 1726-1737. 10.1039/c3pp50041a

7. Seckmeyer, G., Klingbiel, M., Riechelmann, S., Lohse, I., McKenzie, R.L., Liley, J.B., Allen, M.W., Siana, A.-M., Casale, G.R. A critical assessment of two types of personal UV dosimeters. Photochemistry and Photobiology, 88(1): 215-222. 10.1111/j.1751-1097.2011.01018.x