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

Development and characterisation of an ultra-long exposure UV dosimeter

Excessive exposure to solar ultraviolet (UV) radiation is known to have detrimental effects on human health, some of which are cumulative in nature with impacts that may arise after years and decades of exposure. Therefore, it is important that the risk associated with prolonged UV exposure can be investigated; this requires long-term studies in which large-dose measurements can be accurately quantified. Chemically-based UV dosimeters have been widely used to measure personal UV exposure since 1976. Despite the development of electronic UV dosimeters, chemical dosimeters maintain their suitability in human exposure research as versatile, labour- and cost-effective UV monitors that require no power. The main limitation of existing chemical dosimeters is their short dynamic measurement range, as they are saturated after relatively short exposure times. Consequently, prolonged personal UV exposures are estimated either from measurements spanning just a few days, with high uncertainty, or by the regular replacement of dosimeters on location, a practice that increases the cost and effort. A dosimeter that continuously measures longer periods would facilitate the task and provide more reliable estimates of prolonged UV exposures. A new chemical UV dosimeter that meets this demand was developed and fully characterised in this study. The dosimeter, composed of unstabilised solvent cast polyvinyl chloride (PVC) in 16 μm thin film, is able to measure at least three weeks of full day exposure to solar UV radiation under clear sky conditions in summer at subtropical sites. This is twenty times the dose capacity of the most commonly used chemical UV dosimeter, a polysulphone based UV dosimeter. The optimal parameters of the dosimeter’s construction and its dosimetric properties were experimentally investigated and characterised. The results show that the proposed dosimeter is easy to prepare, inexpensive, physically robust and easily analysed using an FTIR spectrometer. It responds mainly to UVB radiation, and hence can be calibrated for quantifying erythemally effective doses for long-term personal exposure studies. The response of the dosimeter to solar UV radiation is independent of temperature and dose rate. It also, exhibits an acceptable angular-error (defined as the deviation of the dosimeter’s relative response from the cosine function when the angle of incident beam is changed) and almost no dark reaction. A field test was conducted to validate the proposed dosimeter with long-term personal UV exposure measurements. The erythemal UV exposures to selected anatomical sites on rotating head form manikins measured with the PVC dosimeter agreed well with the measurements obtained concurrently by a lower dose capacity chemical UV dosimeter, and are on a level with the results reported in earlier similar studies. The characterised dosimeter is a valuable tool for research on the latent effects of cumulative UV exposure on human health. Measurements over longer periods will provide more reliable annual and lifetime exposure estimates as the larger the sample size (length of measurement period), the more accurately the sample will present the population (annual or lifetime UV exposure)

Long-term UV dosimeter based on polyvinyl chloride for plant damage effective UV exposure measurements

Research on the influence of ultraviolet radiation (UV) on terrestrial plants and on its link with other influencing environmental factors requires information on UV exposures, both for a horizontal plane and specific portions of a plant, above and under the canopy. In this research, one set of UV dosimeters based on unstabilized polyvinyl chloride (PVC) were employed to measure the unweighted UVB (UVB) and the biologically effective UV radiation for plant damage (UVBEplant) incident on the leaves of a plant for a month, without having to change the dosimeters. The exposures were compared to the cumulative exposure concurrently measured with six sets of unstabilized polyphenylene oxide (PPO) dosimeters that required changing every four to six days. The difference in exposures between the two types of dosimeters was on average within 11%. The PVC dosimeter is the first reported polymer film dosimeter with a useable range of a month for measuring the plant damaging UV and the UVB exposures to specific parts of a plant. The exposure period of a month for the PVC dosimeter is an extension by a factor of four over the useable range of dosimeters previously reported in the literature for evaluation of the exposure of plants to UV radiation

Solar blue light radiation enhancement during mid to low solar elevation periods under cloud affected skies

Solar blue-violet wavelengths (380 nm - 455 nm) are at the high energy end of the visible spectrum, referred to as ‘high energy visible’ (HEV). Both chronic and acute exposure to these wavelengths have been often highlighted as causes of concern with respect to ocular health. The sun is the source of HEV which reaches the Earth’s surface either directly or after scattering by the atmosphere and clouds. This research has investigated the effect of clouds on HEV for low solar elevation (solar zenith angles between 60° and 80°), simulating time periods when potential ocular exposure in global populations are high during the early morning and late afternoon. The enhancement of ‘bluing’ of the sky due to the influence of clouds was found to increase significantly with the amount of cloud. A method is presented for calculating HEV irradiance from the more commonly measured global solar radiation (300 – 3,000 nm) for all cases when clouds do and do not obscure the sun. The method, when applied to global solar radiation data correlates well with measured HEV within the solar zenith angle range 60° and 80° (R2 = 0.94, MBE = -1.63%, MABE = 10.3% and RMSE = 14.6%). The technique can be used to develop repeatable HEV hazard evaluations for human ocular health applications

Solar radiation and the UV index: an application of numerical integration, trigonometric functions, online education and the modelling process

A short series of practical classroom mathematics activities employing the use of a large and publicly accessible scientific data set are presented for use by students in years 9 and 10. The activities introduce and build understanding of integral calculus and trigonometric functions through the presentation of practical problem solving that focuses on Public Health and developing a personal understanding of solar ultraviolet radiation and the UV Index. The classroom activities are presented using an approach that encourages self-discovery of mathematical concepts by application of mathematical modelling. These activities also develop critical thinking skills through application of data mining, data processing and presentation. They also emphasize the importance of drawing valid conclusions, concepts important to scientific research, statistics and epidemiology

Evaluation of shade profiles while walking in urban environments: A case study from inner suburban Sydney, Australia

Precise shade distributions at the street level are an area of research of increasing importance to provide complete and high spatial and temporal resolutions of the amount and effectiveness of shade. Temporal shade distributions and profiles were evaluated for an inner Sydney tree-lined suburban street at different times of the day using an electronic sun journal (ESJ), providing detailed profiles of shade availability for various times of the day to provide very detailed street-level shade profiles and distributions that are often not included in shade audit methods and models. Further profiles were developed of streets adjoining shopfronts and public parks. Distributions of dense, light and no shade areas were calculated, revealing that tree canopy shade area during the middle of the day is considerably less effective and more prone to gaps than at other times. Distributions calculated using the ESJ were compatible with the paper-based shade auditing with less than 10% variation, whilst the ESJ has revealed a greater resolution of detail of gaps in the shade, thus records a higher amount of areas of no shade. The ESJ is a robust, low cost and portable tool that can efficiently and quickly produce shade profiles during walks in an urban environment, such as streetscapes

A review on the ability of smartphones to detect ultraviolet (UV) radiation and their potential to be used in UV research and for public education purposes

The effects of ultraviolet (UV) radiation on life on Earth have continuously been the subject of research. Over-exposure to UV radiation is harmful, but small amounts of exposure are required for good health. It is, therefore, crucial for humans to optimise their own UV exposure and not exceed UV levels that are sufficient for essential biological functions. Exceeding those levels may increase risk of developing health problems including skin cancer and cataracts. Smartphones have been previously investigated for their ability to detect UV radiation with or without additional devices that monitor personal UV exposure, in order to maintain safe exposure times by individuals. This review presents a comprehensive overview of the current state of smartphones’ use in UV radiation monitoring and prediction. There are four main methods for UV radiation detection or prediction involving the use smartphones, depending on the requirements of the user: devoted software applications developed for smartphones to predict UV Index (UVI), wearable and non-wearable devices that can be used with smartphones to provide real-time UVI, and the use of smartphone image sensors to detect UV radiation. The latter method has been a growing area of research over the last decade. Built-in smartphone image sensors have been investigated for UV radiation detection and the quantification of related atmospheric factors (including aerosols, ozone, clouds and volcanic plumes). The overall practicalities, limitations and challenges are reviewed, specifically in regard to public education. The ubiquitous nature of smartphones can provide an interactive tool when considering public education on the effects and individual monitoring of UV radiation exposure, although social and geographic areas with low socio-economic factors could challenge the usefulness of smartphones. Overall, the review shows that smartphones provide multiple opportunities in different forms to educate users on personal health with respect to UV radiation

Satellite monitoring of environmental solar ultraviolet A (UVA) exposure and irradiance: a review of OMI and GOME-2

Excessive exposure to solar ultraviolet (UV) radiation has damaging effects on life on Earth. High-energy short-wavelength ultraviolet B (UVB) is biologically effective, influencing a range of dermal processes, including the potentially beneficial production of vitamin D. In addition to the damaging effects of UVB, the longer wavelength and more abundant ultraviolet A (UVA) has been shown to be linked to an increased risk of skin cancer. To evaluate this risk requires the monitoring of the solar UVA globally on a time repetitive basis in order to provide an understanding of the environmental solar UVA irradiance and resulting exposures that humans may receive during their normal daily activities. Satellite-based platforms, with the appropriate validation against ground-based instrumentation, can provide global monitoring of the solar UVA environment. Two satellite platforms that currently provide data on the terrestrial UVA environment are the ozone monitoring instrument (OMI) and the global ozone monitoring experiment (GOME-2). The objectives of this review are to provide a summary of the OMI and GOME-2 satellite-based platforms for monitoring the terrestrial UVA environment and to compare the remotely sensed UVA data from these platforms to that from ground-based instrumentation

Spectral response of solvent-cast polyvinyl chloride (PVC) thin film used as a long-term UV dosimeter

The spectral response of solvent-cast polyvinyl chloride (PVC) thin film suitable for use as a long-term UV dosimeter has been determined by measuring the UV induced change in the 1064 cm-1 peak intensity of the PVC's infrared (IR) spectra as a function of the wavelength of the incident radiation. Measurements using cut-off filters, narrow band-pass filters and monochromatic radiation showed that the 16 μm PVC film responds mainly to the UVB band. The maximum response was at 290 nm and decreasing exponentially with wavelength up to about 340 nm independent of temperature and exposure dose. The most suitable concentration (W/V%) of PVC/Tetrahydrofuran solution was found to be 10% and the best thickness for the dosimeter was determined as 16 μm

Optical properties of a long dynamic range chemical UV dosimeter based on solvent cast polyvinyl chloride (PVC)

The dosimetric properties of the recently introduced UV dosimeter based on 16.μm PVC film have been fully characterised. Drying the thin film in air at 50C for at least 28 days was found to be necessary to minimise the temperature effects on the dosimeter response. This research has found that the dosimeter response, previously reported to be mainly to UVB, has no significant dependence on either exposure temperature or dose rate. The dosimeter has negligible dark reaction and responds to the UV radiation with high reproducibility. The dosimeter angular response was found to have a similar pattern as the cosine function but deviates considerably at angles larger than 70 degrees. Dose response curves exhibit monotonically increasing shape and the dosimeter can measure more than 900 SED. This is about 3 weeks of continuous exposure during summer at subtropical sites. Exposures measured by the PVC dosimeter for some anatomical sites exposed to solar radiation for twelve consecutive days were comparable with those concurrently measured by a series of PPO dosimeters and were in line with earlier results reported in similar studies