Peter William Schouten

Evaluation of a high exposure solar UV dosimeter for underwater use

Solar ultraviolet radiation (UV) is known to have a significant effect upon the marine ecosystem. This has been documented by many previous studies using a variety of measurement methods in aquatic environments such as oceans, streams and lakes. Evidence gathered from these investigations has shown that UVB radiation (280–320 nm) can negatively affect numerous aquatic life forms, while UVA radiation (320–400 nm) can both damage and possibly even repair certain types of underwater life. Chemical dosimeters such as polysulphone have been tested to record underwater UV exposures and in turn quantify the relationship between water column depth and dissolved organic carbon levels to the distribution of biologically damaging UV underwater. However, these studies have only been able to intercept UV exposures over relatively short time intervals. This paper reports on the evaluation of a high exposure UV dosimeter for underwater use. The UV dosimeter was fabricated from poly 2,6‐dimethyl‐1,4‐phenylene oxide (PPO) film. This paper presents the dose response, cosine response, exposure additivity and watermarking effect relating to the PPO dosimeter as measured in a controlled underwater environment and will also detail the overnight dark reaction and UVA and visible radiation response of the PPO dosimeter, which can be used for error correction to improve the reliability of the UV data measured by the PPO dosimeters. These results show that this dosimeter has the potential for long‐term underwater UV exposure measurements.

Field calibrations of a long-term UV dosimeter for aquatic UVB exposures

Various methodologies using a wide range of measurement systems have been employed previously in order to determine the amount of UV that could be incident upon various aquatic organisms in a number of different aquatic locales. Broadband meters and spectroradiometers have been employed extensively to take underwater measurements. However, these measurement campaigns are limited by the fact that radiometric equipment requires a human controller, constant power supply and regular calibrations and corrections in order to function properly. Dosimetric measurements have also been made underwater using two distinct types of dosimeter. The first type based on a synthetic chemical, like polysulphone, and the second type based on a biological matter, such as a DNA sample. The studies made using biological dosimeters have displayed very good results, however the time and skill necessary to make these types of dosimeters can outweigh their usefulness. The chemical dosimeters are easier to make and have also provided useable data, but only for short periods of exposure, usually no more than a day. Previous research has shown that Poly (2,6-dimethyl-1,4-phenylene oxide) (PPO) has excellent potential for use as a long-term underwater solar UVB dosimeter. However, there is no documented methodology on how to properly calibrate the PPO dosimeter for water-based measurements and it has yet to be trialled in an outdoors marine environment, either real or simulated. This manuscript shows that calibrations obtained in air can not be transferred to calibrations made in water, calibrations made in one type of water can be employed for another type of water, but only within a certain range of spectral transmission and calibrations made at different depths in the same water type are interchangeable. It was also discovered that changing solar zenith angle had an effect upon calibration data. This research addressed these issues by formulating and developing a calibration methodology required for accurate underwater long-term UVB measurements in the field using the PPO film dosimeter.

Usage of the polyphenylene oxide dosimeter to measure annual solar erythemal exposures

Poly (2, 6‐dimethyl‐1, 4‐phenylene oxide) (PPO) film is a useful dosimetric tool for measuring solar UV in underwater and terrestrial environments. However, little is known about how the response of PPO changes with fluctuations in atmospheric ozone and also to seasonal variations. To resolve this issue this article presents a series of long‐term in‐air solar erythemal response measurements made over a year from 2007 to 2008 with PPO. This data showed that the PPO dose response varies with modulations of the solar spectrum resulting from changes in season and atmospheric ozone. From this, it was recommended that PPO only be calibrated in the season in which it is to be used at the same time as measurements were being made in the field. Extended solar UV measurements made by PPO with a neutral density filter (NDF) based on polyethylene are also detailed. These measurements showed that the lifetime of PPO could be extended by 5 days before saturation. As the dynamic range for PPO is known to be 5 days during summer at a sub‐tropical location, the advantage of using the NDF is that half the number of dosimeters is needed to be fabricated and measured before and after exposure.

Basal and squamous cell carcinoma risks for golfers: an assessment of the influence of tee time for latitudes in the northern and southern hemispheres

This study investigates the influence of tee time to determine the relative basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) risk for weekly single round competition golfers located in the Northern and Southern latitude ranges between 25°, 35°, 45° and 55°. A comparative risk methodology, employing annual erythemally effective ultraviolet (UVE) exposure calculations was used to determine BCC and SCC risk factors for golfers using a regular weekly tee time. Relative risk was found to be proportional to golf tee time with mid morning tee times generally presenting the greatest risk in each latitude range. The greatest contribution toward the risk of developing basal and squamous cell carcinoma was found to occur for golfers beginning weekly rounds mid to late morning, with specific risk factors of 1.47 (BCC) and 1.98 (SCC) in the Northern hemisphere compared with similar maximum risk factors of 1.51 (BCC) and 2.08 (SCC) in the Southern hemisphere occurring at comparable morning tee times. Differences in annual UVE exposure between the golfer and non-golfer were the largest determinant of BCC and SCC risk. Generally, these risks were found to decrease with lower latitude although contribution toward overall risk was influenced strongly by the global time zone of each studied golf course site.

Applicability of the polyphenylene oxide film dosimeter to high UV exposures in aquatic environments

Previous research has proven that the Poly (2,6-dimethyl-1, 4-phenylene oxide) (PPO) dosimeter is capable of receiving both in-air and underwater UV exposures that are significantly greater than those of the more commonly used polysulphone dosimeter, within a range of accuracy close to what would be expected of dosimetric measurements made in-air provided that the necessary calibrations are completed correctly by factoring in different atmospheric column ozone levels, SZA ranges, varying water turbidity and DOM levels. However, there is yet to be an investigation detailing the performance of the PPO dosimeter and its ability to measure UV in an actual field environment over an extended period of time. This research aims to bridge this gap in the knowledge by presenting a measurement campaign carried out in two real world aquatic environments and a simulated sea water environment using a batch of PPO dosimeters set at different depths and aligned to a range of different angles and geographical directions by means of attachment to a custom built dosimeter submersible float (DSF) unit over the space of a year at a sub-tropical location. Results obtained from this measurement campaign were used to compute a K(d) value for the sea water in each particular season. These K(d) values where found to be in close agreement to standalone K(d) values derived from results taken using a standard calibrated spectrometer in the same sea water.

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.

Solar Ultraviolet Protection Provided by Human Head Hair

The solar erythemal UV irradiances through human hair and the protection from UV provided by human head hair have been investigated for a solar zenith angle (SZA) range of 17–51° for the conditions of a head upright in full sun, a head upright in shade and a head in full sun tilted toward the sun. The two hair lengths investigated were 49.1 ± 7.1 mm for the short type and 109.5 ± 5.5 mm for the long type. For the head upright in full sun, the irradiances through the hair ranged from 0.75 to 1.4 SED h−1 for SZA <25° and <0.6 SED h−1 in shade. The ultraviolet protection factor (UPF) ranged from approximately 5 to 17 in full sun, with the UPF increasing with higher SZA. The longer hair provided a lower UPF than the shorter hair and for the head oriented toward the sun, there was a marginally lower UPF than for the upright head. This research shows that the UV exposure limits to the scalp through hair can be exceeded within short timeframes and provides important information to assist employers to comply with Workplace Health and Safety legislation.

Direct comparison between the angular distributions of the erythemal and eye-damaging UV irradiances: A pilot study

Several broadband ultraviolet (UV) radiation angular distribution investigations have been previously presented. As the biologically damaging effectiveness of UV radiation is known to be wavelength dependent, it is necessary to expand this research into the distribution of the spectral UV. UV radiation is also susceptible to Rayleigh and Mie scattering processes, both of which are completely wavelength dependent. Additionally, the majority of previous measurements detailing the biologically damaging effect of spectral UV radiation have been oriented with respect to the horizontal plane or in a plane directed towards the sun (sun-normal), with the irradiance weighted against action spectra formulated specifically for human skin and tissue. However, the human body consists of very few horizontal or sun-normal surfaces. Extending the previous research by measuring the distribution of the spectral irradiance across the sky for the complete terrestrial solar UV waveband and weighting it against erythemal, photoconjunctivital and photokeratital action spectra allowed for the analysis of the differences between the biologically effective irradiance (UV(BE)) values intercepted at different orientations and the effect of scattering processes upon the homogeneity of these UV(BE) distributions. It was established that under the local atmospheric environment, the distribution profile of the UV(BE) for each biological response was anisotropic, with the highest intensities generally intercepted at inclination angles situated between the horizontal and vertical planes along orientations closely coinciding with the sun-normal. A finding from this was that the angular distributions of the erythemal UV(BE) and the photoconjunctivital UV(BE) were different, due to the differential scattering between the shorter and longer UV wavelengths within the atmosphere.

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.

Characterisation and evaluation of a miniaturised polyphenylene oxide dosimeter for ultraviolet exposures

Dosimeters are used in measuring received ultraviolet (UV) radiation by humans and plants. Previously dosimeters 3.0cm×3.0cm weighing 0.6g, using poly(2,6-dimethyl-1,4-phenylene oxide) (PPO)(1) as the photoactive material have been used. A smaller 1.0cm×1.5cm flexible PPO dosimeter weighing 0.05g has been developed and characterised in this research. Laboratory and field studies show that the miniaturised dosimeter measures comparative results to the larger dosimeters for cosine response, dark reaction and dose response. The smaller, flexible dosimeters are also more applicable for use on curved surfaces and have less impact on the orientation of plant leaves due to their decreased mass. This research has also shown that miniaturised PPO dosimeters can be successfully employed on plant and human subjects to accurately determine biologically active UV distributions. The miniaturised PPO dosimeters allow for more measurements over an exposed area and the PPO film allows for measurements to be made for periods longer than 1day. The combination of smaller size and longevity of the photoactive material allows for more flexibility in future UV field research resulting in an increase in the potential number of environments where UV dosimeters can be deployed.