Measuring the influence of UV reflection from vertical metal surfaces on humans

Abstract

Erythemal UV exposure for individuals involved in outside activities are affected according to surrounding structures in an urban environment. Occupational UV exposure is likely to increase by the effects of surrounding structures. UV reflections from surrounding structures, in this case vertical metal walls, were investigated for their influence on erythemal UV exposure in the southern hemisphere. Multiple dosimeters were placed at specific features on head forms, for three different vertical wall conditions, measured at hourly intervals, providing a more detailed representation of the effect of nearby (north facing) reflective wall, non-reflective wall and no wall on UV exposure for a construction worker facing the wall direction. Two types of metal sheeting walls were investigated, with the first type (shiny and smooth in appearance) showing results that indicate the UV reflectance from this surface can increase the average erythemal UV exposure by at least 20% and up to an average of 50% for certain facial positions, compared to no wall and up to 300% compared to a non reflective wall. A second metal sheeting type coated with colour, does not show as much influence on UV exposure for larger solar zenith angles compared to the first type of metal sheeting, but for smaller solar zenith angles provides an influence that approaches similar erythemal UV exposure to that when no wall is present. The time to reach the exposure limits defined by regulatory bodies for occupational UV exposure can be decreased if the first type of metal sheeting is in proximity to an outdoor worker. The experimental method of this study leads to discussion of how metal surfaces used in the construction industry physically reflect UV radiation. The conclusion is that albedo, which is traditionally used to measure UV reflection, is not an appropriate quantity to explore UV reflection from vertical metal surfaces. This may be due to the reason that metal surfaces seem to involve specular reflection as well as diffuse reflection.

Influence of reflected UV irradiance on occupational exposure from combinations of reflective wall surfaces

“…Previous published studies have shown that time of day and season are important to the reflective capacity of the surface types investigated. 22,23 The atmospheric conditions for the wall data as reported in Turner and Parisi 21 was clear with low to no clouds. The ozone was 255-259 DU (zinc aluminium) and 252-275 DU ( pale green) as provided by the U.S. National Aeronautics and Space Administration's Ozone Monitoring Instrument.…”

“…Data were obtained by constructing "walls" and "corners" combined with the use of polysulphone dosimetry and manikin head forms. Data for the walls from a previous study 21 obtained in May 2008 in Autumn, were compared to data for the corners which were collected during Autumn 2009 (over five days in March and April for both surface corner types). Details of the constructed walls are found elsewhere.…”

“…Details of the constructed walls are found elsewhere. 21 The corners were constructed using the same materials as the walls, using two types of standard building materials (in Australia): zinc aluminium coated steel and pale green painted coated steel with a trapezoidal profile. Corners were made with two sheets of each metal type of size 90 cm × 100 cm at right angles to each other (Fig.…”

“…This was the same strategy used in the wall study. 21 Each manikin head form had thirteen polysulphone dosimeters attached in the same position on each manikin. These positions were vertex, forehead, nose, chin, chest, both cheeks, both ears, back of head, back of neck, and both shoulders (Fig.…”

“…13 Increased UV exposure to the body has been shown to occur for specific types of man-made surfaces in urban settings. 21 However the urban setting is not just made of single walls, but combinations of walls (for example, corners). This study will determine if a worker located within a combination of two walls (a "corner") with full solar UV exposure will be exposed in different quantities than a worker located near an unbroken flat wall of the same material, and if so, what that impact will mean to the worker's UV exposure.…”