Quantification of the protection from solar ultraviolet radiation provided by tree shade

The effect of tree parameters on the solar erythemal UV and UVA in tree shade on a horizontal plane at ground level during a Southern Hemisphere summer was measured. The parameters investigated were tree canopy transmission in the visible waveband (VT), tree canopy width, tree height and height of the start of the tree canopy (CH). Of these factors, the VT and CH have an influence on the UV irradiances in the tree shade with the others not having any significant effect. The shade ratios (defined as the ratio of the UV in the tree shade to that in full sun) for erythemal UV ranged from 0.71 to 0.42, 0.54 to 0.29 and 0.63 to 0.41 for morning, noon and afternoon respectively. The shade ratios for UVA ranged from 0.61 to 0.28, 0.50 to 0.22 and 0.49 to 0.29 for morning, noon and afternoon respectively. The UV exposures in the tree shade decreased with the VT. The spectral shade ratio decreased with increasing wavelength. For the sample of trees investigated, the decrease in the spectral shade ratio was approximately 42% at 400 nm compared to the shade ratio at 300 nm. Despite the protection by the tree shade, significant UV in the tree shade of approximately 4 MED (minimum erythemal dose) were received for the latitude in this research on a cloud free summer day on a horizontal plane over a two hour period centred about solar noon

Ambient and personal solar ultraviolet exposure measurements

An understanding of the solar terrestrial ultraviolet (UV) environment is necessary for the minimisation of solar UV exposures to humans and reduction of the risk of human sun-related disorders. In the Centre for Astronomy and Atmospheric Research at the University of Southern Queensland (USQ), Toowoomba, the ambient and personal solar UV exposures are measured in different environments. Outdoor, temperature stabilised meters provide the erythemal UV and UVA throughout the day to a web page. At the sub-tropical latitude of this site, anti-correlations were measured between atmospheric ozone variations due to natural atmospheric processes and erythemal UV exposures. Increases of up to 14% over 5 days in the daily UV exposures to a horizontal plane were recorded. The personal erythemal UV exposures in gum tree shade have been quantified with UV dosimeters. These dosimeters are fabricated from polysulphone in thin film form. Quality assurance procedures are in place to produce film of reproducible and constant thickness, as changes in the film thickness can cause errors of up to 37% in the dose response. When summed over the whole day for each day in summer, the exposures in the gum tree shade were in excess of the erythemal UV exposures for horizontal plane incidence in full sun for an entire summer in England. The UV spectrum in gum tree shade was measured and the spectral shade ratio decreased with increasing wavelength for all of the trees. The tree shade is not as effective at providing protection at the shorter wavelengths where the erythema, actinic and DNA action spectra have a higher relative effectiveness

Solar UV radiation measurements with polysulphone

[Abstract]: In order to optimize the UV exposure of humans, an understanding of the complex solar UV environment is necessary. Dosimeters based on either biological or chemical UV dosimeters have been developed and are a powerful tool in the research on the solar UV environment. Polysulphone which has achieved wide spread use as a dosimeter in research on UV exposures resulting from the sun or artificial sources is discussed

Variations in UV exposure due to reflected UV radiation in the urban environment

Excessive UV radiation exposure to outdoor workers is a serious issue, particularly when many outdoors workers generally exceed nominal safety UV exposure levels. In Australia, construction workers regularly use (UV reflective) metal surfaces in building construction, due to practicality and financial viability issues. Previous work has shown that reflection from vertical metallic surfaces can increase total exposure by approximately 20% and facial exposure by 50%. This work has been extended by considering the same situation in another season (spring) in comparison to the original study (autumn and winter). The results from spring measurements do not match those from the original study, and theories why will be presented. In addition, different orientations and combinations of vertical surfaces have been investigated, including comparing UV exposures from horizontal, vertical and inclined surfaces and exposures incurred from corners compared to exposures single vertical surfaces. The results of these investigations were varied, and through this presentation will be presented and discussed

Patterns in surface distribution of human exposure to solar ultraviolet

[Abstract]: A method for the three dimensional representation of erythemally effective ultraviolet radiation (UVery) incident to the human body has been developed from a series of polysulphone dosimeter (PS) measurements to the face, neck, arms, legs and hands of a manikin model. The technique has been used to represent a series of human UVery exposure patterns in the solar zenith angle (SZA) range 30o-50o measured in an open environment in Toowoomba, Australia (27.5oS 151.9oE). The human body representations of exposure presented here improve upon existing techniques to represent the UVery exposure to complex body shape topography, providing for the first time, estimates of exposure that take whole body shading effects into account from high density PS dosimeter measurements

Patterns in the received facial UV exposure of school children measured at a subtropical latitude

Polysulphone 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 (25.3oS 152.9oE). The results of a series of 1 hour 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 Jm-2 (1σ), to 99 33 Jm-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 Jm-2. Facial exposure relative to the received ambient UV increased to the nose at higher (winter) Solar Zenith Angles (SZA) 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

Personal solar UV exposure measurements employing modified polysulphone with an extended dynamic range

Polysulphone dosimeters using a simple to use filter have been developed and tested to provide an extended dynamic measurement range of personal solar UV exposures over an extended period (3 to 6 days). At a Southern Hemisphere subtropical site (27.68S, 151.98E), the dynamic range of the filtered polysulphone allowed measurements of erythemal exposures to approximately 100 minimum erythemal dose (MED) for a change in optical absorbance at 330 nm (DA330) of 0.35. In comparison, unfiltered polysulphone dosimeters were exposed to approximately 8 MED for the same DA330. The error associated with the use of the filtered polysulphone dosimeters is of the order of 615%, compared with 610% of the unfiltered variety. The developed filtered polysulphone dosimeter system allowed the measurement of erythemal UV exposures over 3 to 6 days at a subtropical site without the need to replace the dosimeters because of saturation. The results show that longer-term measurement programs of personal solar UV have been made more feasible with the use of these polysulphone dosimeters with an extended dynamic range compared with unfiltered polysulphone dosimeters

Ozone and ultraviolet radiation

Imagine if the earth’s protective atmosphere did not exist and the earth was subjected to the harmful ultraviolet energy from the sun. Life as we know would not exist. Changes in the earth’s layer of atmospheric ozone may be occurring as a result of human activities. This is generating concerns in the community about increases in terrestrial ultraviolet radiation and the associated adverse effects on humans, plants and animals

Why do UV levels vary?

Have you ever suffered the excrutiating pain and discomfort of a severe sunburn followed by the unsightly peeling of the skin? Have you ever wondered why you may receive a sunburn even on a partially cloudy day? There are a number of factors that influence the amount of solar ultraviolet radiation reaching the earth’s surface

Investigation of unstabilized polyvinyl chloride (PVC) for use as a long-term UV dosimeter: preliminary results

A new chemical UV dosimeter with a larger dose-capacity than the existing chemical dosimeters has been investigated for long-term UV measurements. Unstabilized Polyvinyl chloride (PVC), cast in 40 μm thick film, has been found to respond to at least 745 SED (Standard Erythema Dose = 100 J/m2) of erythemal solar UV radiation. This is equivalent to about two to three summer weeks of exposure in subtropical sites. The UV-induced changes in the PVC dosimeter were quantified using a Fourier Transform Infrared (FTIR) spectrophotometer and the decrease in the absorption intensity of the 1064 cm-1 peak was employed to quantify these changes. Dose response curves have been established by relating the decrease in the PVC dosimeter's absorption intensity at 1064 cm-1 to the corresponding erythemal UV exposure. The spectral response of the dosimeter was measured and found to be comparable to the erythema action spectrum. Some other optical characteristics of the dosimeter, such as the dose-rate dependency and the angular response were analysed. The dosimeter was found to have the potential to measure long periods of exposure to solar UV radiation as well as exposures to artificial UV