Ambient Solar UVR, Personal Exposure and Protection

Ambient solar ultraviolet radiation (UVR) has been monitored around Australia by the Australian Radiation Laboratory (ARL) and its successor ARPANSA since the mid 1980's using a network of radiometric detectors and a spectroradiometer (SRM) for spectral measurements, based in Melbourne. In a continent the size of Australia, the levels vary markedly, basically following a latitude gradient increasing towards the equator but with local geographical and weather effects also evident. ARL also conducts personal exposure studies of various population groups in collaboration with other research centres to gather information on what fraction of the ambient UVR people receive. ARL also undertakes studies on the UVR protection provided by sunscreens, clothing, hats, sunglasses and other materials in an attempt to improve UVR protection used by the public. J Epidemiol, 1999 ; 9 : S115-S122.

Australia has high levels of solar UVR, due mainly to its geographical position between 10° and 43° S.During summer in the southern hemisphere, the earth's elliptical orbit brings it closer to the sun than during the northern summer, resulting in an additional 7% solar UVR intensity.This, coupled with clearer atmospheric conditions and the more significant ozone depletion observed over the Antarctic, may result in a measured ambient UVR which is 10 to 15% higher than for comparable locations in the northern hemisphere').These high UVR levels coupled with an outdoor lifestyle result in high rates of both non melanoma skin cancer (NMSC) and melanoma, with approximately 1200 deaths and 200,000 new cases of NMSC a year and a cost to the Australian community of the order of $300 Million per year.This is already a major problem and the prospects of increases in solar UVR at the earth's surface of 5 to 7 % due to long term ozone depletion 1) can only add to the problem.This would lead to an increase in NMSC and melanoma if outdoor exposure remained constant.A programme to determine the solar UVR levels the Australian population is exposed to was implemented by ARL, along with personal exposure studies to quantify outdoor exposures and to identify and target at risk groups and provide information to public education campaigns to try to change behaviour and further reduce exposure.The goal of a reduction in the UVR exposure of the population has been actively pursued by the state Cancer Councils with their education programmes such as SunSmart.The introduction of the UVlndex 2) may provide a significant educational opportunity to impact on people's behaviour.

Ambient Solar UVR
The measurement network used to monitor ambient solar UVR around Australia covers all of the capital cities and a number of other major population centres and has been described in detail elsewhere s, 3,4).Since 1992/93, Solar Light 501 UVBiometers have been in use in all major capitals.Spectral measurements of solar UVR across the wavelength range 280 to 400nm at lnm intervals have been made on selected clear days using a Spex 1680B double monochromator spectroradiometer system since 1986, with calibration against 1000W tungsten halogen standard lamps traceable to the CSIRO National Measurement Laboratory.An automated, weather proof system has been installed on the roof of the laboratory and will commence continuous daylight spectral mea-surements in all weather conditions by March 1999.

Personal Exposures
Polysulphone (PS) film has been employed as a dosimeter of solar UVR in personal exposure studies since 1976 [5][6][7][8][9][10][11][12][13][14][15][16][17][18].The dose response of PS film has been characterised with simultaneous solar spectral measurements and PS exposures 12) and a number of such studies in conjunction with other research organizations 12.13,15.16)have been undertaken.More recently, ARL has been involved in a personal exposure study using small electronic UV detector/datalogger systems pioneered by Diffey and Saunders 19) recording UV exposure on a minute by minute basis.This study done in conjunction with the Anti-Cancer Council of Victoria (ACCV), used an ARL modified system as used in 19) to determine the effect of behaviour on the UVR exposure.

Protection
Australia has standards 20-22) covering protection against solar UVR by sunscreens, sunglasses, sun protective clothing, protective eyewear and shadecloth.The SunSmart campaigns run by the various state cancer councils and the Australian Cancer Society have raised awareness amongst the population to the extent that the demand for information on the W protection provided by items of protection is high and increasing.ARL undertakes laboratory measurements on a variety of such items to assess their UVR protection.

RESULTS AND DISCUSSION
Ambient Solar UVR.

Measurements
of ambient biologically effective solar UVR (UVReff) from a number of countries 3. 23-28) increase with decreasing latitude (Figure 1).With ozone depletion of the order of 3% per decade at mid-latitudes, it is unlikely that long-term ozone depletion effects on the measured UV levels will be observed for some years 29) due to cloud cover variations.The latitude gradient of solar UVR is clearly evident in Figure 1, as is the fact that Australia has very high levels, between 4000 to 8000 Minumum Erythemal Doses (MEDs -1 MED is 200 J/m2 effective 25) weighted with the erythemal response of the CIE 30)) per year.The levels of non melanoma skin cancer (NMSC) are also very high and the variation with latitude is shown in Figure 1 31).
The introduction of the UVlndex 2), implemented in Australia during the summer of 1995/96, allows people to become familiar with the levels of solar UVR associated with different weather at different times of the year.The TV/news reports now give the daily UV index and show the variation of UVR with time of day at the end of each day as well as giving the UVlndex predictions for the next day as computed by the Australian Bureau of Meteorology.
The UVlndex is the maximum value of biologically effective solar UVR during the day, rather than the value at solar noon, and forecasts are generally accurate for clear sky conditions.Figure 2 shows the effect of clouds on the solar UVR  Australian capital cities for 1997/98 are shown in Figure 4 for comparison.
Personal Exposure to Solar UVR While knowledge of the ambient levels of solar UVR is vital in studies related to skin cancer and melanoma incidence, an important aspect is personal exposure.Personal exposure of the general population to solar UVR is a complex relationship between activity, behaviour, location (both geographical and local) and ambient UVR levels.Personal exposure studies provide information on various aspects of this interaction and a number of such studies using a variety of subject groups have been undertaken over the past 20 years 5-18).Not all results agree but some generalizations can be made.These are summarized below: • Males have higher UVR exposures than females 14-16) receiving between 50 and 100% more UVR, because they generally spend more time outdoors.• Measured UVR exposures are proportional to ambient UVR for similar subject groups 14-16) Schoolchildren in the UK 14,17) received 5 to 6% of daily total ambient while in Australia they received 5 to 10% 15) and 4 to 8% 16) respectively.Each of 3 locations in Queensland 16) showed boys had exposures proportional to ambient as did girls, although these proportions were different.The effect behaviour and activity can have on the UVR exposures of two subjects participating in outdoor activities (picnicking and walking) is shown in Figure 5.The picnicker in the shade of a tree has a low and almost constant exposure while the walker who is predominately in the open has a larger exposure which is proportional to ambient.The potential dose to the walker is large, yet full use of personal protection would reduce this dose substantially (to 10 to 50% of what it might have been).

Protection against Solar UVR Behavioural changes
Education campaigns on the hazards of sun exposure designed to change people's behaviour have started to have measurable effects.This is true (and observable) with use of personal protection.The application of an SPF 15+ or greater sunscreen to all the exposed areas of skin as well as wearing a hat, good quality sunglasses and well-designed clothing provides significant protection (50 to 90% reduction in exposure).
Sun avoidance (minimizing time outdoors near solar noon, and use of available shade) is also encouraged and applies to recreation as well as work.Reduction of an individual's total UVR exposure at work is of little value if appropriate behaviour is not adopted during recreational activities.

Legislative and Environmental changes
Modifying the environment, in particular providing shade and UVR protective structures for areas that in the past were in complete sun (in schools, playgrounds and outdoor recreation areas) can also help reduce human exposure.Organisations such as schools and employers are considered responsible for providing a non-hazardous environment for their students or employees.A number of policy documents have been released in Australia covering the provision of shade 32-34).Legislation can also be used to aid in protection against solar UVR.In many states of Australia, primary schools are adopting the rule that students without hats are barred from playing in the schoolgrounds at recess and lunch times.Employers of outdoor workers must provide their employees with sun protective items and the employees are required to use these. Protection.
The increased interest in UVR protection applies not only to sunscreens, sunglasses and industrial eyewear, clothing and hats, but also to materials, shadecloth, roofing and construction plastics 35), car windscreens, side windows, autoglass and tints 36) and even tents.These topics are summarized elsewhere 37.38).

Sunglasses
Sunglasses complying with AS 1067 21) will provide considerable protection.Compliance with the standard became mandatory in 1988, and in the 10 years since, the UVR protective properties of sunglasses has improved significantly, while sunglasses which fail the standard or which have poor UVR protective properties have been almost completely eliminated from the market place.

Sunscreens
The Australian Sunscreen Standard 20) was recently revised and raised the maximum allowed Sun Protection Factor (SPF) claim from 15+ to 30+.The standard sets in vitro test methods for the determination of UVA transmittance of sunscreens.Education campaigns emphasizing correct application are required, since surveys indicate that sunscreens are applied at a thickness half that used in laboratory in vivo SPF determinations 39), with a consequent reduction in the SPF achieved in practice.Sunscreens should not be the sole method of protection but used in conjunction with clothing (where good protection is independent of the method of application), to protect areas of the body not covered by garments.

Clothing
Cancer Council education campaigns have long urged the use of clothing in conjunction with hats and sunscreens as UVR protection.Initial studies showed one third of summer weight clothing (cotton and polyester-cotton) provided less protection than an SPF 15+ sunscreen, with protection factors as low as 5 to 10 37).Given the increasing interest in protection, both recreationally and occupationally, a rating scheme for clothing which would guarantee garments had sufficient UVR protection was required.The Ultraviolet Protection Factor (UPF) scheme for clothing was devised by ARL 37), and incorporated into a standard 1).The upper limit of the scheme, UPF 50+, provides substantial protection and should prevent the escalation of claims by manufacturers.Swing tags provide the measured UPF rating and protection category and have a protection message from the Australian Cancer Society on the reverse side.In excess of 7 million such tags have been attached to UVR rated garments.Design considerations (long sleeves and collars) are encouraged in sun protective clothing in an effort to maximize the body coverage and thus the protection provided.
Australia was the first country with a standard on Sun Protective Clothing 22).Work has continued and revisions to that standard such as a wet test method and a stretch test method are pending.Work is now being done around the world on the factors which affect the UVR protection provided by clothing and these are discussed elsewhere 38).Standards now also exist in the UK 40) and are imminent in the US and Europe.Solar UVR rated clothing may not provide sufficient protection against artificial sources of UVR 41), as people have developed erythema when wearing UPF rated clothing in occupational situations (welding).State Cancer Councils sell sunscreens, sunglasses, UVR rated clothing and hats to the public at a reasonable cost, an important consideration in attempts to widen their use.Successful educational campaigns mean there is now a demand for commercial products which provide UVR protection.ARL publishes a free guide42) which lists products (and the companies that produce them) that provide protection against solar UVR.
Education campaigns and changing the behaviour of the population offers the biggest potential for reducing exposure and the health effects due to solar UVR.Changing people's behaviour both when outdoors and to using personal UVR protection can prove difficult to achieve, as a visit to any Australian beach in summer will demonstrate.Improved forms of protection against solar UVR as well as better strategies to implement their use can also help.Education campaigns targetting the groups most at risk and identifying clearly the factors which have important effects on solar UVR exposure of the population requires input from many different areas of research.

Figure 3 .
Figure 3.The daily variation of effective UVR for a typical summer day in MEDS/hr (left scale) compared with the UVlndex (right scale).

MELBOURNE - 6 Figure 5 .
Figure 5.The variation of UVR exposure with time for two subjects undertaking outdoor activities, picnicking and walking.
for Melbourne for consecutive days in March.March 2 was cloudy, but with a break in the clouds near noon, while March 1 was clear all day.Both days had similar measured UVlndices (8.5 vs 9.1) yet the measured daily total solar UVR was significantly different (10.8 MEDs vs 24.4 MEDS).Daily total UVR is a better measure of the overall levels of ambient solar UVR while UVlndex is more useful as an indicator of the maximum potential hazard.Figure3shows the typical daily variation of solar UVR and a comparison between UVlndex and MEDs.At solar noon, 5 MEDs per hour (sufficient UVR to induce mild erythema in sensitive skin in 12 minutes) correspond to a UVlndex of 11.2.Measured UVIndices for six LATITUDE Figure 1.Measured annual biologically effective solar UVR in MEDs/yr for a number of northern and southern hemisphere sites 27-28).Also shown are the non-melanoma skin cancer rates for Australia "' levels Melbourne Time of Day (hrs) Figure 2. The variation of solar UVR measured in Melbourne for two days in March, showing the effects of cloud cover on UVlndex and daily total UVR.Clear Sky Solar UVReff-Summer Time of Day • UVR exposures of large groups of subjects are non uniformly distributed, generally following log normal distributions 14,16.17)• Some subjects have consistently high or consistently low exposures in comparison to the mean 10.13-17) from a tenth to ten times the mean 17).Population groups are not homo- Queensland Health, 1995; ISBN 0 7242 6605 4. 34.Greenwood JS, Soulos GP, Thomas ND.Under cover: Guidelines for shade planning and design.NSW Cancer Council and NSW Health Dept, Sydney 1998.35.Toomey SJ, Gies HP, Roy CR.UVR Protection offered by shadecloths and polycarbonates.Radiation Prot in Australia, 1995; 13: 50-54.36.Gies HP, Roy CR, Wang Zongli.Ultraviolet radiation protection factors for clear and tinted automobile windscreens.Radiation Prot in Australia, 1992; 10: 91-94.37. Gies HP, Roy CR, Elliott G, Wang Zongli.Ultraviolet radiation protection factors (UPF) for clothing.Health Physics, 1994; 67: 131-139.38.Gies PH, Roy CR, Toomey S, McLennan A. Protection against solar UV radiation.Mutation Res, 1998; 422: 15-