Nathan Downs

Variation of the enhanced biologically damaging solar UV due to clouds

The variation of the biologically damaging solar UV (UVBE) enhanced by clouds above that of clear sky UVBE has been investigated. This was undertaken for summer through to winter for SZA of 5 to 60 degrees employing an integrated automatic cloud and spectral UV measurement system that recorded the solar UV spectra and the sky images at five minute intervals. The UVBE calculated with action spectra with higher relative effectiveness in the UVA produced the lower percentage of cloud enhanced cases. The DNA UVBE provided the highest percentage of cloud enhanced cases compared to the total number of UV scans with 2.2% cloud enhanced cases. As a comparison, the plant and fish melanoma UVBE provided the lowest percentage of cloud enhanced cases with 0.6 to 0.8% cloud enhanced cases. For the cases of cloud enhanced UVBE, the average ratio of the measured UVBE to calculated cloud free UVBE for the photokeratitis, cataracts, plant, generalized plant damage and fish melanoma action spectra was 1.21 to 1.25. In comparison, the highest value of 1.4 was for the DNA action spectrum.

Comparison of human facial UV exposure at high and low latitudes and the potential impact on dermal vitamin D production

The results presented in this paper allow for the estimation of the monthly UV exposure of the human facial region at various locations across the earth. The technique allows a graphical representation of the UV exposures over the face. The erythemal UV exposures as well as the vitamin D exposures to the human facial region have been investigated. The results gained in this paper, for a clear sky and constant ozone indicate that the suns capability to promote the development of vitamin D in the human body does not follow the erythemal UV irradiances, in particular at high latitudes. For Amsterdam (52 degrees N) in late winter, approximately 20% more UV is required to produce 215 J m(-2) of vitamin D weighted UV than erythemal UV.

Patterns in the Received Facial UV Exposure of School Children Measured at a Subtropical Latitude

Polysulfone (PS) dosimeters have been employed to measure the erythemally effective UV exposure to the vertex, nose, cheek, chin and side facial sites of 45 volunteer high school students from Hervey Bay, Australia (25.3°S 152.9°E). The results of a series of 1 h outdoor sport trials (basketball and soccer) found the mean student facial exposure, determined as the arithmetic average of facial site exposures of unprotected students (no hat) to protected students (hat), varied from 140 ± 82 J m−2 (1σ) to 99 ± 33 J m−2 (1σ), respectively. All hourly student facial exposures recorded over the study period were found to exceed the National Health and Medical Research Council’s adopted safe daily limit of 30 J m−2. Facial exposure relative to the received ambient UV increased to the nose at higher (winter) solar zenith angles (SZAs) compared with lower (summer) SZA ranges for both protected and unprotected students. The protection offered by the broad‐brimmed hats was reduced significantly to the lower chin facial site at the higher SZA range, indicating that the style of hat used offers best protection in summer to the upper facial regions at most risk of receiving a high exposure when no hat protection is used. Variations to specific student facial exposure sites were measured between both basketball and soccer players. Variation in student facial exposure was further examined with respect to cloud cover and comparisons to manikin headform measurements were also made. The study results indicate that hats alone are not adequate forms of sun protection in a school environment. Schools aiming to achieve acceptable safe limits of facial exposure may need to further consider the effectiveness of hat protection with increasing SZA, cloud cover and head position relative to the sun that is specific to the scheduled outdoor activity.

Three Dimensional Visualisation of Human Facial Exposure to Solar Ultraviolet

A three dimensional computer model of the human face has been developed to represent solar ultraviolet exposures recorded by dosimeter measurements on a manikin headform under low cloud conditions and various solar zenith angles. Additionally, polysulfone dosimeters have been successfully miniaturised to provide the detailed measurements required across the face. The headform used in this research was scanned at 709 individual locations to make a wireframe mesh consisting of 18 vertical contours and 49 horizontal contours covering half the manikins frontal facial topography. Additionally, the back of the headform and neck have also been scanned at 576 locations. Each scanned location has been used as a viable dosimeter position on the headform and represents a grid intersection point on the developed computer wireframe. A series of exposures recorded by dosimeters have been translated into three dimensional exposure ratio maps, representing ambient solar ultraviolet exposure. High dosimeter density has allowed for the development of individual topographic contour models which take into account complex variation in the face and improve upon previously employed techniques which utilise fewer dosimeters to interpolate exposure across facial contours. Exposure ratios for solar zenith angle ranges of 0 degrees -30 degrees, 30 degrees -50 degrees, and 50 degrees -80 degrees have been developed.

Mean exposure fractions of human body solar UV exposure patterns for application in different ambient climates

In this research, the erythemally effective UV measured using miniaturized polysulphone dosimeters to over 1250 individual body sites and collected over a 4‐year period is presented relative to the total exposed skin surface area (SSA) of a life‐size manikin model. A new term is also introduced, the mean exposure fraction (MEF). The MEF is used to weight modeled or measured horizontal plane UV exposures to the total unprotected SSA of an individual and is defined as the ratio of exposure per unit area received by the unprotected skin surfaces of the body relative to the exposure received on a horizontal plane. The MEF has been calculated for a range of solar zenith angles (SZA) to provide a sunburning energy data set weighted to the actual SSA of a typically clothed individual. For this research, the MEF was determined as 0.15, 0.26 and 0.41 in the SZA ranges 0°–30°, 30°–50° and 50°–80° providing information that can be used in a variety of different ambient, latitudinal and seasonal climates where total human body UV exposure information is not available.

Understanding the UVA environment at a sub-tropical site and its consequent impact on human UVA exposure

Daily UVA and erythemal irradiance data on a horizontal plane at a sub-tropical site were measured during a period from March 2000 to February 2001. On a relative basis, UVA radiation was shown to be a greater concern to human exposure during the winter months than summer months. In summer (December to February), the peak daily UVA exposure was 205 J cm(-2) and in winter (June to August), the minimum daily value was 19 J cm(-2). The peak daily UVery exposure was 37 MED in summer and the winter minimum was 4 MED. The occupational work day UVA exposure to the vertex of the head was estimated using the collected UV data. The outdoor workers received 89% of the available UVA radiation whilst the home workers received 18% of the available ambient UVA radiation. This result parallels the exposure patterns of these two population groups, with the outdoor workers spending most of the working week outdoors, whilst the home workers spend small, intermittent time periods outdoors in the sun.

Measurements of the upper body ultraviolet exposure to golfers: non‐melanoma skin cancer risk, and the potential benefits of exposure to sunlight

Background: Geographically, Queensland presents an extreme ultraviolet exposure climate to members of the public engaged in outdoor recreational activity. The risk of developing a skin cancer or an eye disease as a result of incidental exposure to naturally occurring ultraviolet radiation in the outdoor environment is proportionately high in a Queensland population compared with fair‐skinned population groups residing in comparable Northern Hemisphere latitudes. In contrast to these risks, elderly members of this high growth population group have been reported to be vitamin D deficient. The risks and potential benefits of exposure to sunlight in southern Queensland are assessed in this study with respect to recreational golfing. This sport is a popular recreational activity for the Queensland population and must be played during daylight hours.

Ultraviolet exposures in different playground settings: a cohort study of measurements performed in a school population.

Background: Solar erythemally effective ultraviolet (UVE) measured on the face, neck, arms, hands and legs of a cohort of school children was investigated with respect to student movement about a school environment located in Southern Queensland.

Solar UV exposures measured simultaneously to all arbitrarily oriented leaves on a plant

The possible ramifications of climate change include the influence it has upon the amount of cloud cover in the atmosphere. Clouds cause significant variation in the solar UV radiation reaching the earths surface and in turn the amount incident on ecosystems. The consequences of changes in solar UV radiation delivered to ecosystems due to climate change may be significant and should be investigated. Plants are an integral part of the world wide ecological balance, and research has shown they are affected by variations in solar UV radiation. Therefore research into the influence of solar UV radiation on plants is of particular significance. However, this requires a means of obtaining detailed information on the solar UV radiation received by plants. This research describes a newly developed dosimetric technique employed to gather information on solar UV radiation incident to the leaves of plants in combination with the measurement of spectral irradiances in order to provide an accurate method of collecting detailed information on the solar UV radiation affecting the canopy and lower leaf layers of individual plants. Variations in the measurements take into account the inclination and orientation of each leaf investigated, as well as the influence of shading by other leaves in the plant canopy.

Measurements of occupational ultraviolet exposure and the implications of timetabled yard duty for school teachers in Queensland, Australia: preliminary results.

Simultaneous personal measurements of the occupational ultraviolet exposure weighted to the International Commission on Non-Ionising Radiation Protection hazard sensitivity spectrum (UVICNIRP) were made over a five week period (44 person-days) in the second half of the summer school term of 2012 in Queensland, Australia for individual high school teachers located at latitudes of 27.5°S and 23.5°S. These teachers were employed for the duration of the study in a predominately indoor classroom teaching role, excluding mandatory periods of lunch time yard duty and school sport supervisions. Data is presented from personal measurements made to the shirt collar using polyphenylene oxide (PPO) film UV dosimeters. UVICNIRP exposure data is presented for each week of the study period for the shirt collar measurement site and are further expressed relative to the measured ambient horizontal plane exposure. Personal exposures were correlated with time outdoors, showing a higher exposure trend on days when teachers were required to supervise outdoor areas for more than 2h per week (mean daily exposure: 168Jm(-2)UVICNIRP±5Jm(-2) (1σ)) compared to the study average (mean daily exposure: 115Jm(-2)UVICNIRP±91Jm(-2) (1σ)). Time spent in an open playground environment was found to be the most critical factor influencing the occupational UVICNIRP exposure. A linear model was developed showing a correlation (R(2)=0.77) between the time teachers spent on yard duty and UVICNIRP exposure, expressed relative to ambient. The research findings indicate a greater reduction in personal exposure can be achieved by timetabling for yard duty periods in playground areas which offer more shade from trees and surrounding buildings. All mean daily personal exposures measured at the shirt collar site were higher than the ICNIRP occupational daily exposure limit of 30Jm(-2) for outdoor workers.