The effects of body size and orientation on ultraviolet radiation exposure

Determinants of Sunburn and Sun Protection of Agricultural Workers During Occupational and Recreational Activities

OBJECTIVE

The aim of this study was to identify determinants of occupational sunburn in agricultural workers and assess their occupational and recreational sun protection habits.

METHODS

Specific surveys of agricultural workers in Switzerland and France were conducted (N = 1538). Multivariate logistic regressions identified occupational sunburn determinants. Occupational and recreational sun protection habits were estimated and correlated.

RESULTS

One-year occupational and recreational sunburn prevalences were 19.8% and 11.5%, respectively. Occupational sunburn increased with having a recent recreational sunburn, highly sensitive skin, young age, high perceived skin cancer risk, using sunscreen, and not wearing a hat. Correlation between protection habits during work and leisure was substantial (rs 0.5 to 0.7). Skin health knowledge was high and pro-tanning attitude moderate.

CONCLUSION

Potentially modifiable sunburn determinants and suboptimal recreational and occupational sun protection practices were identified in agricultural workers. Refining and tailoring sun protection messages targeting the agricultural sector are needed.

Reduction of Solar UV Radiation Due to Urban High-Rise Buildings--A Coupled Modelling Study

Solar UV radiation has both adverse and beneficial effects to human health. Using models (a radiative transfer model coupled to a building shading model), together with satellite and surface measurements, we studied the un-obstructed and obstructed UV environments in a sub-tropical urban environment featured with relatively high pollution (aerosol) loadings and high-rise buildings. Seasonal patterns of the erythemal UV exposure rates were governed by solar zenith angles, seasonal variations of aerosol loadings and cloud effects. The radiative transfer modelling results agreed with measurements of erythemal UV exposure rates and spectral irradiances in UVA and UVB ranges. High-rise buildings and narrow road width (height to width, H/W, ratios up to 15) reduced the modelled total UV (UVA+UVB) radiation and leave 10% of the un-obstructed exposure rate at ground-level at noon. No more than 80% of the un-obstructed exposure rate was received in the open area surrounded by 20-storey buildings. Our modelled reduction of UVB radiation in the urban environment was consistent with similar measurements obtained for Australia. However, our results in more extreme environments (higher H/W ratios) were for the first time reported, with 18% of the un-obstructed exposure rate remained at the ground-level center of the street canyon.

A general model to predict individual exposure to solar UV by using ambient irradiance data

Excessive exposure to solar ultraviolet (UV) is the main cause of skin cancer. Specific prevention should be further developed to target overexposed or highly vulnerable populations. A better characterisation of anatomical UV exposure patterns is however needed for specific prevention. To develop a regression model for predicting the UV exposure ratio (ER, ratio between the anatomical dose and the corresponding ground level dose) for each body site without requiring individual measurements. A 3D numeric model (SimUVEx) was used to compute ER for various body sites and postures. A multiple fractional polynomial regression analysis was performed to identify predictors of ER. The regression model used simulation data and its performance was tested on an independent data set. Two input variables were sufficient to explain ER: the cosine of the maximal daily solar zenith angle and the fraction of the sky visible from the body site. The regression model was in good agreement with the simulated data ER (R(2)=0.988). Relative errors up to +20% and -10% were found in daily doses predictions, whereas an average relative error of only 2.4% (-0.03% to 5.4%) was found in yearly dose predictions. The regression model predicts accurately ER and UV doses on the basis of readily available data such as global UV erythemal irradiance measured at ground surface stations or inferred from satellite information. It renders the development of exposure data on a wide temporal and geographical scale possible and opens broad perspectives for epidemiological studies and skin cancer prevention.

A numeric model to simulate solar individual ultraviolet exposure

Exposure to solar ultraviolet (UV) light is the main causative factor for skin cancer. UV exposure depends on environmental and individual factors. Individual exposure data remain scarce and development of alternative assessment methods is greatly needed. We developed a model simulating human exposure to solar UV. The model predicts the dose and distribution of UV exposure received on the basis of ground irradiation and morphological data. Standard 3D computer graphics techniques were adapted to develop a rendering engine that estimates the solar exposure of a virtual manikin depicted as a triangle mesh surface. The amount of solar energy received by each triangle was calculated, taking into account reflected, direct and diffuse radiation, and shading from other body parts. Dosimetric measurements (n = 54) were conducted in field conditions using a foam manikin as surrogate for an exposed individual. Dosimetric results were compared to the model predictions. The model predicted exposure to solar UV adequately. The symmetric mean absolute percentage error was 13%. Half of the predictions were within 17% range of the measurements. This model provides a tool to assess outdoor occupational and recreational UV exposures, without necessitating time-consuming individual dosimetry, with numerous potential uses in skin cancer prevention and research.

Estimating natural UV personal exposure with radiative transfer calculations

The following study has investigated whether straightforward radiative transfer calculations can be used to adequately document natural UV personal exposure. The method was evaluated by comparing the results with erythemal doses accumulated by polysulphone films positioned on mannequins. The calculations succeeded in reproducing the variability associated with changing solar zenith angle and atmospheric conditions. A possible use of the model has been illustrated by estimating the daily exposure during 1 y of a hypothetical office worker, according to a simple occupational schedule. The calculated daily exposures indicated the importance of holiday periods in the risk of acute overexposure and in the total yearly dose.

Effective exposure to solar UV in building workers: influence of local and individual factors

Excessive exposure to solar UV light is the main cause of skin cancers in humans. UV exposure depends on environmental as well as individual factors related to activity. Although outdoor occupational activities contribute significantly to the individual dose received, data on effective exposure are scarce and limited to a few occupations. A study was undertaken in order to assess effective short-term exposure among building workers and characterize the influence of individual and local factors on exposure. The effective exposure of construction workers in a mountainous area in the southern part of Switzerland was investigated through short-term dosimetry (97 dosimeters). Three altitudes, of about 500, 1500 and 2500 m were considered. Individual measurements over 20 working periods were performed using Spore film dosimeters on five body locations. The postural activity of workers was concomitantly recorded and static UV measurements were also performed. Effective exposure among building workers was high and exceeded occupational recommendations, for all individuals for at least one body location. The mean daily UV dose in plain was 11.9 SED (0.0-31.3 SED), in middle mountain 21.4 SED (6.6-46.8 SED) and in high mountain 28.6 SED (0.0-91.1 SED). Measured doses between workers and anatomical locations exhibited a high variability, stressing the role of local exposure conditions and individual factors. Short-term effective exposure ranged between 0 and 200% of ambient irradiation, indicating the occurrence of intense, subacute exposures. A predictive irradiation model was developed to investigate the role of individual factors. Posture and orientation were found to account for at least 38% of the total variance of relative individual exposure, and were also found to account more than altitude on the total variance of effective daily exposures. Targeted sensitization actions through professional information channels and specific prevention messages are recommended. Altitude outdoor workers should also benefit from preventive medical examination.

Facultative skin pigmentation in caucasians: an objective biological indicator of lifetime exposure to ultraviolet radiation?

To investigate age and gender trends in facultative and constitutive skin pigmentation we measured skin pigmentation non-invasively and objectively by skin reflectance spectroscopy in 653 caucasians (336 females and 317 males; mean age 38 years, range 0-85) who were not using artificial tanning devices. In all subjects, measurements were performed in the late winter and pre-spring period at five sites exposed to ultraviolet (UV) radiation: the forehead, the upper chest, the upper back and the lateral and medial aspects of the upper arm, and in UV-unexposed buttock skin. Constitutive pigmentation at the buttocks was highest in the first years of life and then decreased substantially during the first two decades of life (P < 0.01). After the age of 25 years, buttock pigmentation remained at a constant level (P = 0.20). There was no gender difference in constitutive pigmentation. Facultative skin pigmentation increased with age for all the measured sites with the highest levels found at the lateral aspect of the upper arm. Based on observations in this study we propose the idea of a 'sun exposure index' (SEI) for individuals, based on objective measurements of skin pigmentation. The SEI is calculated as the increase in facultative pigmentation above the constitutive level and is expressed as a percentage of the constitutive level. The SEI appeared to be related to cumulative lifetime UV exposure and may be used in epidemiological research as an objective estimate of UV exposure at different body sites in caucasians.

The facial distribution of erythemal ultraviolet exposure in south-east Queensland

This paper presents a method for the evaluation of the distribution of the facial erythemal UV exposure and the erythemal UV exposure per unit area of the face using only eight dosimeters located on the vertex of the head, forehead, nose, chin, left and right ears and left and right cheeks. An overall picture of the parts of the face receiving high UV exposures is provided. The distribution of the erythemal UV exposure to the human face at a subtropical latitude was shown to change with time of year and with cloud cover. On two days with similar solar zenith angles, the ratio of the erythemal UV exposure to the nose compared with that on a horizontal plane changed from 0.47 to 0.84 with increased cloud cover. At the same time, the total erythemal exposure per unit area of the face dropped from 122 to 56 ml cm-2. Although the absolute exposures decreased, the nose received a relatively high exposure.