Minimum Exposure Limits and Measured Relationships Between the Vitamin D, Erythema and International Commission on Non-Ionizing Radiation Protection Solar Ultraviolet

Low dose ultraviolet B irradiation at 308 nm with light-emitting diode device effectively increases serum levels of 25(OH)D

This animal study aimed to elucidate the relationship of low-dose, narrow-band UVB at 308 nm with vitamin D synthesis. C57BL/6 female mice, at 3 weeks-of-age, were randomly divided into the following six groups (n = 6 at each time point of vitamin D measurement), which were: (1) normal diet without UVB irradiation; (2) VDd diet without UVB irradiation; and (3)-(6) VDd diet with 308 nm-UVB irradiation of 12.5, 25, 50, and 100 μω/cm2, respectively. All of the groups needing UVB irradiation received an exposure of 10 min per day, five days per week, and a duration of 3-5 weeks. The mice recovering from severe VDd (plasma total 25-hydroxyvitamin D level increasing from approximately 3 to over 30 ng/mL) only occurred in groups with a UVB irradiation dosage of either 50 or 100 μω/cm2. The optimal, estimated dosage for mice to recover from severe VDd was 355 mJ/cm2 within 3 weeks. Low-dose, narrow-band UVB irradiation at 308 nm is effective in improving VDd in mice. The results obtained, in addition to the especially small side effects of the above UVB irradiation formula, could be further translated to treating VDd-related disorders.

Solar Ultraviolet Radiation Exposure among Outdoor Workers in Three Canadian Provinces

Introduction

Solar ultraviolet radiation (UVR) exposure places outdoor workers at risk of skin cancer and exposure is difficult to control. In response, the Sun Safety at Work Canada (SSAWC) project was undertaken (2014–2016). The purpose of this substudy was to characterize the UVR exposure levels of outdoor workers in the SSAWC project.

Methods

Thirteen workplaces in the provinces of British Columbia, Ontario, and Nova Scotia participated in an exposure monitoring campaign (late summer/early fall 2016). Study participants were workers from power utilities and municipalities. Participants wore a UVR measurement badge (light-sensitive polysulfone plastic) on their wrist, shoulder, or hardhat. Badge calibration and absorbance measurements were performed in the AusSun Research Lab. Personal UVR doses are presented as standard erythemal doses (SED) and compared with the internationally recommended exposure limit (1.3 SED), as well as to the total available UVR by date. Generalized linear models were used to examine determinants of solar UVR for personal UVR dose (for both SED and percent of ambient UVR). Models considered badge placement, date, province, industry, main job task, and the hours spent outdoors.

Results

Mean personal UVR dose of participating workers was 6.1 SED (nearly 5× the recommended limit). Just 14% of workers experienced ‘acceptable’ levels of solar radiation; 10% were exposed at >10 times the limit. In univariate analyses, workers in Ontario had the highest levels (mean 7.3 SED), but even in the lowest exposed province (British Columbia), the mean personal UVR dose was 4.5 SED. Utility workers had double the exposure of municipal workers (10.4 and 5.5 SED, respectively). In the determinants of exposure models, the differences by province were muted, but utility line workers and those in general maintenance had higher predicted exposures. Those who wore their badge on their hardhat also had higher values of SED in the fully adjusted determinants models.

Conclusions

Solar ultraviolet overexposure among outdoor workers is a concern, even in a country like Canada with relatively low ambient UVR. Implementation of sun safety programs should be supported in an effort to reduce exposure in this vulnerable group of workers.