Colin Roy

Solar and ultraviolet radiation

Solar UVR is the most important source of ultraviolet radiation (UVR) to which the world’s population is exposed. The long-term effects of these UVR exposures are dealt with in later chapters but a brief description of the biological effects of UVR is given here and an overview of the measurement of UVR is also provided. The chapter provides a detailed exploration of the range of factors that affect solar UVR at the earth’s surface and includes a summary of solar UVR levels around the world. The role of personal behavior when outdoors, perhaps the most important factor determining an individual’s exposure to solar UVR, is then examined as being the main potential avenue to modify and reduce these exposures. The chapter concludes with an overview of artificial sources of UVR and their associated hazards.

PERSONAL DOSIMETRY OF SOLAR UV RADIATION FOR DIFFERENT OUTDOOR ACTIVITIES

Abstract Quantifying individual exposure to ultraviolet radiation (UVR) is critical to understanding the etiology of a number of diseases including nonmelanotic and melanotic skin cancers. Measurements of personal exposure to solar UVR were made in Hobart, Tasmania in February (summer) 1991 for six different outdoor activities using UVR‐sensitive polysulfone (PS) film attached at seven anatomical sites. Concurrent behavioral and environmental observations were also made. To date many studies have relied on subject recall to quantify past solar UVR exposures. To gain insight into the accuracy of subject recall the measured UVR exposures received by different subjects using the PS film were compared to those calculated from personal diaries and ambient solar UVB levels from a monitoring station. In general, when UVR exposure activities took place under close supervision, good correlations were obtained between the PS badges and the ambient measurements/diaries approach. Ultraviolet radiation exposures for the field study involving 94 subjects engaged in a number of outdoor activities are presented.

Global Solar UV Index: Australian measurements, forecasts and comparison with the UK.

Abstract The 2002 revision of the UV index (UVI) issued by the World Health Organisation (WHO), the World Meteorological Office (WMO), the United Nations Environment Programme (UNEP) and the International Commission on Non-Ionizing Radiation Protection (ICNIRP) (World Health Organization [2002] Global Solar UV Index: A Practical Guide. WHO, Geneva) was motivated by the need to further standardize the use and presentation of the UVI. Awareness of the hazards of solar UV radiation (UVR) is generally high in Australia, but more effective use of the UVI will assist in promoting further changes to the populations sun exposure behavior. UVI levels for a number of cities around Australia as measured by the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA), covering the time period 1996–2000, are presented. Also shown are UVI forecasts from the Australian Bureau of Meteorology (BOM). Agreement between the BOM data and the measurements varies depending on the location but is within 2 UVI units approximately 75% of the time. UVI levels are supplied to the media, and in summer values in excess of 12–14 are regularly recorded, although the more northerly locations occasionally reach 16 and 17. The factors affecting the solar UVR environment and the measured UVI are also discussed and compared against measurements from the UK.

SOLAR UVR EXPOSURES OF THREE GROUPS OF OUTDOOR WORKERS ON THE SUNSHINE COAST, QUEENSLAND

The solar ultraviolet radiation (UVR) exposures of three groups of outdoor workers, physical education (PE) teachers, ground staff/gardeners and lifeguards were measured using UVR‐sensitive polysulfone (PS) film badges. The exposures all took place on the Sunshine Coast, Queensland over 5 consecutive weekdays in November 1992. For the three groups, the shoulder badges received greater UVR exposures than the chest badges, in agreement with previous studies. The PE teachers received the highest UVR exposures while the lifeguards received the least. One of the 5 days of the study was overcast with some rain showers and UVR doses for this day for all groups were significantly lower than on the other 4 days, however the ratio of exposure to ambient remained relatively constant. All groups had measured UVR exposures in excess of occupational guidelines, indicating that protective measures, including education and behavior modification, which are becoming much more common in occupational situations in Australia, are both timely and necessary.

Solar UVR Exposures of Primary School Children at Three Locations in Queensland

Abstract— The ultraviolet radiation (UVR) exposures of primary school children in Brisbane, Toowoomba and Mackay (latitudes 27°30′, 27°33′ and 21°15′ south, respectively) were assessed over a period of 2 weeks at each location using UVR‐sensitive polysulfone (PS) film badges attached at the shoulder. The students filled in questionnaires on their time spent outdoors for each day of the study. These data in conjunction with the ambient UVR measured by a detector/datalogger unit at each site were used to correlate the calculated exposures with those measured using the PS badges. Overall, the questionnaires indicated that the males spent more time outdoors and had higher measured UVR exposures than females. For both boys and girls at each location, there was a strong correlation between the mean measured UVR exposure and the ambient solar UVR at that location.

Surface UV radiation over Australia, 1979–1992: Effects of ozone and cloud cover changes on variations of UV radiation

Time series of daily erythemal ultraviolet radiation (UVR) exposure, ozone, and cloud cover were analyzed over the Australian continent using data sets from the NASA Total Ozone Mapping Spectrometer (TOMS) from 1979–1992. The TOMS UVR exposures showed good agreement with data from surface observations. Using a relationship derived from comparisons of the TOMS partial cloud reflectivities with surface cloud cover observations, the TOMS reflectivities were converted into estimates of cloud cover for several Australian regions. It was shown that the deseasonalized time series of UVR exposures can be statistically described as a linear function of ozone and cloud cover anomalies. Results of a trend analysis indicated statistically significant increases in UVR exposures of 10% decade−1 in the summer months in the tropics. These were associated with a simultaneous depletion of ozone and a decrease in cloud cover. Midlatitudinal regions showed no significant trends of UVR. It was found that variations of ozone and UVR over Australia were significantly influenced by the quasi-biennial oscillation (QBO). An increase in zonal wind strength of 20 m s−1 was correlative with reductions of ozone of 1.7% and enhancements of UVR exposures of 2.2%. An increase in solar radio flux of 100×10−22 W m−2 (Hz)−1 was associated with significant reductions of UVR of 5–10% in the tropical and subtropical regions in summer. The results suggested that enhancements in summer UVR exposures of about 10–20% above the climatological average might be expected in years in which the QBO is in its westerly phase and the solar cycle is at its minimum.

Correlations between Reported and Measured Ultraviolet Radiation Exposure of Mothers and Young Children

Abstract Cumulative and intermittent sun exposure are risk factors for skin cancer, highlighting the need to monitor exposure during childhood. There is currently very little available information concerning the accuracy of self-reported levels of sun exposure, particularly for very young children. In this study, UV radiation (UVR) exposure measured by polysulfone dosimeters worn on the wrist was compared with a measure of estimated exposure using a diary based on recall at the end of the 4 day study period and ambient dosimetric measures. Results of the study indicate that the relative UVR exposures expressed as a fraction of daily total ambient received during the 4 day period by young children and mothers are similar. A high level of association was obtained for the estimated levels of exposure between young children and their mothers. Moderate correlations were evident for dosimeter readings of mother and child on weekends with no significant association on weekdays. The association between estimated exposure and dosimeter readings was poor and needs improvement. This may be achieved by greater consideration of structural and environmental factors that influence the levels of UVR exposure received by individuals and by increasing the level of specificity in the measurement instruments. Methodological issues such as recall of exposure after several days, quantity of sun exposure and more precise measurement of grades of exposure when outside may have more impact than previously expected, and further information is being sought with a larger sample for exposure during the summer months.

Measurements of the UVR Protection Provided by Hats Used at School

Abstract The importance of protection against solar ultraviolet radiation (UVR) in childhood has lead to SunSmart policies at Australian schools, in particular primary schools, where children are encouraged and in many cases required to wear hats at school. Hat styles change regularly and the UVR protection provided by some of the hat types currently used and recommended for sun protection by the various Australian state cancer councils had not been previously evaluated. The UVR protection of the hats was measured using UVR sensitive polysulphone film badges attached to different facial sites on rotating headforms. The sun protection type hats included in this study were broad-brimmed hats, “bucket hats” and legionnaires hats. Baseball caps, which are very popular, were also included. The broad-brimmed hats and bucket hats provided the most UVR protection for the six different sites about the face and head. Legionnaires hats also provided satisfactory UVR protection, but the caps did not provide UVR protection to many of the facial sites. The highest measured UVR protection factors for facial sites other than the forehead were 8 to 10, indicating that, while some hats can be effective, they need to be used in combination with other forms of UVR protection.

The measurement of solar ultraviolet radiation

High skin cancer rates, stratospheric ozone depletion and increased public interest and concern have resulted in a strong demand for solar ultraviolet radiation measurements and information. The Australian Radiation Laboratory (ARL) has been involved since the mid-1980s in the measurement of solar ultraviolet radiation (UVR) using spectroradiometers (SRM) and a network of broadband detectors at 18 sites in Australia and Antarctica and in Singapore through a collaborative agreement with the Singapore Institute of Science and Forensic Medicine. Measurement locations range from equatorial (Singapore, 1.3 degrees N) through tropical (Darwin, 12.4 degrees S) to polar (Mawson, 67.6 degrees S) and as a result there are many difficulties associated with maintenance and calibration of the network detectors, and transfer of data to ensure an accurate and reliable data collection. Calibration procedures for the various detectors involve the comparison with simultaneous spectral measurements using a portable SRM incorporating a double monochromator, calibrated against traceable standard lamps. Laboratory measurements of cosine response and responsivity are also made. Detectors are intercompared at the Yallambie site for a number of months before installation at another location. As an additional check on the calibrations, computer models of solar UVR at the earths surface for days with clear sky and known ozone are compared with the UV radiometer measurements.

UVR Emissions from Solaria in Australia and Implications for the Regulation Process

To assist in the development of the 2008 Australian/New Zealand standard on solaria and related regulations, Australian Radiation Protection and Nuclear Safety Agency scientists visited a number of tanning establishments during 2008 to measure the intensity and spectral distribution of the ultraviolet radiation (UVR) emissions from a range of solaria. The 2002 Australian/New Zealand Standard “Solaria for cosmetic purposes” (AS/NZS 2635) allowed a maximum UVR output from solaria of UV Index 60, a compromise between the solarium industry who wanted no upper limit and the health agencies who wanted to limit intensity. Of the 20 solaria examined in detail, only one had emissions of intensity less than UV Index 12, typical of mid‐latitude summer sunlight, 15 units emitted more than UV Index 20, while three units emitted at intensities above UV Index 36, the maximum allowed by the new standard, AS/NZS 2635 (2008) and would thus not comply. UVA emissions ranged from 98 W · m−2 up to a maximum of 438 W · m−2, more than six times the UVA content of mid‐latitude summer sunshine. The results indicate that solaria users in Australia have access to solaria that are high intensity units with both significantly higher UVB and UVA emissions than sunlight, with implications for resultant adverse health effects.