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 to 51 degrees for the conditions of a head upright in full sun, a head upright in shade and a head in full sun tilted towards 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 for SZA less than 25 degrees and less than 0.6 SED/h 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 towards 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 (UVBE) values intercepted at different orientations and the effect of scattering processes upon the homogeneity of these UVBE distributions. It was established that under the local atmospheric environment, the distribution profile of the UVBE 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 UVBE and the photoconjunctivital UVBE were different, due to the differential scattering between the shorter and longer UV wavelengths within the atmosphere

Quantitative evaluation of the personal erythemal ultraviolet exposure in a car

The erythemal ultraviolet (UV) exposures to the right hand, mid-arm, shoulder, chin, nose and left and right sides of the face have been evaluated in a car from the large family class and a car from the small car class. In the small car, the highest exposure site received 2.2 times more exposure than the highest exposure site in the larger car. In both cars, the highest erythemal exposures to the body sites are to the body region of the right shoulder, arm and hand. Over a six hour period, the erythemal exposure to the right shoulder of a person in the driver’s seat of the small car was 3.1 mJ cm-2

Comparison of biologically damaging spectral solar ultraviolet radiation at a southern hemisphere sub-tropical site

The first data set of a complete year of biologically damaging spectral UV at a sub-tropical latitude in the SH has been presented. The new data provides a baseline data set against which comparisons can be made in the future to establish if there have been any long term trends in the biologically damaging UV. The general shape of the variation of the daily biologically damaging exposures through the year depends on the relative response of the various action spectra at the different wavelengths. The ratio of the daily erythemal to actinic exposures drops by approximately 20 to 25% from winter to summer. The ratio of the erythemal to DNA exposures drops by approximately 50% over the same period. In contrast, the ratio of the erythemal to plant damage exposures is higher in summer compared to winter. This is due to the changes in the relative proportion of UVA to UVB wavebands and relative responses of the different action spectra. The relative changes for the different action spectra show that the erythemal action spectrum cannot be used as a proxy for other biologically damaging responses

The erythemal ultraviolet exposure for humans in greenhouses

A spectrum evaluator has been employed to evaluate the erythemal exposure in late spring and late summer at three sites and five orientations at each site inside a glass greenhouse with black shadecloth over the glass roof. The maximum in the erythemal irradiance in the greenhouse is not necessarily at noon. Over a day, the maximum erythemal exposure occurred on the eastern side of the greenhouse in the morning and on the western side in the afternoon. The erythemal irradiance on the eastern side in the morning was higher by 26% and 50% for horizontal and vertical surfaces respectively compared to the same site at noon. On the western side the irradiance was higher by 45% and 78% for the horizontal and vertical surfaces respectively compared to the same site at noon. The erythemal irradiance inside the greenhouse does not vary as much during the day as it does outside, for example, for horizontal surfaces, the ratio of the erythemal irradiance outside to the average inside the greenhouse varies from 66 to 112 to 74 for the morning, noon and afternoon periods respectively. Over a six hour period, the erythemal exposure to the shoulder for a standing posture in the greenhouse was 5mJ cm-2