| PrefaceSolar ultraviolet (UV) radiation is an important environmental factor that affects human health. Moderate UV radiation triggers vitamin D synthesis in the skin, contributes to protection against breast cancer, prostrate cancer and non Hodgkin's lymphoma et al. However, excessive solar UV radiation has various direct and indirect effects on human health, which may lead to skin cancer, cataract, immune suppression, photoaging, and other ailments. Based on data from 2006, the World Health Organization reported that globally around 1.5 million Disability Adjusted Life Years (0.1% of the total global burden of diseases) are lost every year due to excessive UV exposure. Skin cancer and cataract are among the primary public health problems and are consequently of special concern.The diurnal variation of solar UV radiation on a horizontal surface is well understood, but little attention has been paid to the study of this variation at anatomical sites of interest. The understanding of diurnal variations of UV radiation at anatomical sites may be more helpful in developing ways to protect humans from the harmful effects of UV radiation. Due to the depletion of ozone, the increasing life expectancy and the changing modern life style, it is likely that our lifetime exposure to UV radiation is greater than that of previous generations which may further increase UV-related disease burden. These situations put forward higher requirements for the quantification and protection of the individual UV exposure. Therefore, to characterize the diurnal variations, the UV exposure values are measured at 15min intervals using Solar-UV Sensors and a rotating manikin in Shenyang (41°51'N,123°27'E) and Sanya (18°19'N,109°42'E), P R. China for each seasons. The diurnal variations in solar UV radiation at the shoulder, the forehead, and the chest were analyzed. An improved understanding of solar UV exposure variation will be helpful in deriving recommendations for how to avoid excessive exposure to certain parts of the body.Public health authorities have made extensive efforts to educate the public about the risks of excessive solar UV exposure over the past several decades. Recognition of the regional, seasonal and individual messages, a more targeted policy for solar-UV health communications needs to be developed. In order to explore a simple and effective protective measures, the orientable manikin is programmed manually to scan 12 positions with horizontal orientation and 30°steps of azimuth angle (0,360°] which started form the position of oriented towards the sun at each time. By clarify the specific role of the orientation to the UV exposure of anatomic sites, it will enhance the public awareness of protection for the shadow, change the public's behavior of neglecting to avoid excessive exposure in outdoor activities of the past, and advocate the public to avoid direct sunlight as well as correct use of sun protection measures actively. These can effectively prevent UV damage.This study also suggested that quantifying individual UV exposure by the exposure ratio of different seasons, different times during the day, its assessment may be more focused and more detailed, especially for the special groups of outdoor activities in the morning and evening hours. Furthermore, by quantifying the exposure doses at different anatomical sites, including the eyes, the dose-effect relationship between UV exposure dose and disease profile can be better understood.Materials and Methods1. Rotating manikinThe rotating manikin consists of two parts. The upper part is the manikin and the lower part is a powered stage. The UV dose was measured using a set of Solar-UV Sensors attached to anatomical sites of interest on the manikin, included the forehead, the right eye, the left cheek, the shoulders, and the chest.The lower part supports and automatically rotates the manikin at a uniform rate. When the power is turned on, the rotational speed of the manikin was one rotation every six seconds for this study. When the power is turned off, the manikin could rotated manually.2. UV exposure measurementThe dose measurement data in Shenyang, Liaoning (41°51'N,123°27'E, mean altitude of 50m) was collected during one week around the equinoxes and solstices and the data in Sanya, Hainan (18°19'N,109°42'E, mean altitude of 3.55-4.5m) was collected in mid and late May as well as around the winter solstice. The data was recorded at 15 min intervals. All of the measurements were acquired on sunny days with clear skies or minimal cloud cover. Two UV sensors was also placed horizontal or vertical in an exposed, unobstructed area near the rotating manikin. These two sensors were activated over the same experimental period in order to measure the ambient solar UV dose (the horizontal one) and the UV exposure on the vertical plane (the vertical one) in the locality of the manikin as control measurement. The cumulative solar UV at typical anatomical sites were measured for 112 days in total, and the measurement of UV exposure at different orientations was conducted for 12 days in total. In addition, to compare the fitting calculation results to the measurements data, the UV exposure to the manikin in Shaoxing, Zhejiang (30°1'N,120°58', mean altitude of 5-6m) was measured during about one week around the autumnal equinox in 2009, and the field monitoring was conducted as that above-mentioned methods in Shenyang and Sanya regions.3. Data analysisThe unscrambling, recording, checking and analysis of all data were executed by the software of Microsoft Excel 2003 and SPSS13.0.Results1. The diurnal variations in solar UV radiation at the forehead and the shoulder were similar to those associated with a horizontal control measurement, which reached a single UV peak exposure dose during the measurement made at around solar noon.2. The diurnal variations at the eye and the cheek exhibited bimodal distributions, with two peaks or platform distributions in all the seasons in Shenyang and Sanya except in winter in Shenyang, which were much similar to those associated with the vertical plane. In winter in Shenyang, the diurnal variations at the eye and the cheek were both unimodal distributions as the horizontal plane.3. The diurnal variations in solar UV radiation at the chest were similar to those associated with a horizontal measurement except in May in Sanya. In May in Sanya, the diurnal variations at the chest exhibited bimodal distributions, with two peaks significantly.4. In the whole solar elevation angle range, the increase in UV exposure at the forehead and the shoulder were following the rise of the angles. The UV exposure peaks at the eye, the cheek and the chest were measured at solar elevation angle about 30°,40°and 60°, respectively.5. The solar UV exposure at the forehead, shoulder and on the horizontal plane was strongest in the 4h midday period. During this period, they all received more than 54.79% of the total 8h UV exposure. While the solar UV exposure at the eye and the cheek were relatively high during the period of in the early morning and late afternoon.6. The five anatomical sites can be ordered by increasing daily UV exposure on the selected measurement days as follows:eye, cheek, chest, forehead, and shoulder. However, the dose at the forehead was slightly higher than at the shoulder in winter in Shenyang. when the sorting criterion was changed to the ratio between the UV exposure of a particular anatomical site, the order for these sites remained unchanged.7. The seasons can be ordered by increasing UV exposure ratios in Shenyang, it was as follows:winer>spring and fall>summer. In Sanya, it was winter (in Jannary) >summer (in May). There was a significant seasonal difference in the exposure ratios, the maximum was in winter and the minimum was in summer. The assessment of individual UV exposure should adopt in different exposure ratios of seasons. 8. In the front of the sun towards a certain orentation of view, the eye reach the peak in the sun elevation angle of about 30°during the day. While in the back towards a certain orentation of the sun, the UV exposure of the eye rise with the solar elevation angle increased in the whole range of solar elevation angle.9. The orientation impact the UV exposure of different anatomical parts significantly. For the eyes, the orientation of straied from the sun about 30°will effectively reduce UV exposure.Conclusions1. The diurnal variations in solar UV radiation at the forehead and the shoulder were similar to those associated with a horizontal control measurement, which were exhibited unimodal distributions; the diurnal variations at the chest exhibited unimodal distribution in all the seasons except in summer in Sanya that it was bimodal distributions; while The diurnal variations at the eye and the cheek were much similar to those associated with the vertical plane, which exhibited bimodal distributions, with two peaks in all the seasons except in winter in Shenyang that it was unimodal distribution.2. The UV exposure doses at the forehead and shoulder sites increased with increasing solar elevation angle. The UV exposure peaks at the chest was measured at solar elevation angle about 60°. The UV exposure peaks at the eye, the cheek were measured at solar elevation angle about 30°and 40°, respectively.3. The daily exposure ratios were different between the seasons. While the daily UV exposure ratios in the summer were the lowest, the daily ratios in the winter were the highest across the various anatomical sites. It's reasonable that quantifying individual UV exposure by the exposure ratio of different seasons.4. The orientation impact the UV exposure of different anatomical parts significantly. For the eyes, the orientation of straied from the sun about 30°will effectively reduce UV exposure.5. Geographical location, seasonal and other factors determine the scope of the local solar elevation angle, and then influence seasonal diurnal distribution of the UV exposure at various anatomical sites of the individual. Bsed on the actual situation, corresponding more targeted solar ultraviolet health guidelines needs to be developed. |
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