Siddhnath Sudhanshu1, Pramod Upadhyay2, Monashish Sahu3, Vinita Rawat4, Vijayalakshmi Bhatia1. 1. 1Department of Endocrinology,Sanjay Gandhi Postgraduate Institute of Medical Sciences,Lucknow 226014,Uttar Pradesh,India. 2. 2National Institute of Immunology,New Delhi,India. 3. 3Max Hospital,New Delhi,India. 4. 4Department of Microbiology,Government Medical College,Haldwani,Uttarakhand,India.
Abstract
OBJECTIVE: To document the effect of season and environmental pollution on UVB irradiance; and to estimate cutaneous vitamin D synthesis in village women in different seasons. DESIGN: Radiant UVB energy was measured by a spectroradiometer in different seasons and, in April and May, on successive days in open areas at the city outskirts, at a crowded inner-city area and the villages of our participants. Clothing, outdoor activity pattern and serum 25-hydroxycholecalciferol (25(OH)D) levels were documented. SETTING: Rural north India, latitude 26·8°N. SUBJECTS: Pregnant women (n 139, aged 20-40 years). RESULTS: UVB irradiance ranged from 56 µW/cm2 in January to 470 µW/cm2 in June. Proportion of skin exposed was 18·5 % in summer and 9·5 % in winter. Mean (sd) daily duration of sun exposure was 3·2 (0·2) h during winter and 2·1 (0·4) h during summer. Cutaneous vitamin D synthesis was estimated to be 19·25 µg (770 IU) during winter and 37·25 µg (1490 IU) during summer. Mean (sd) serum 25(OH)D was 28 (15) nmol/l during winter (92 % of participants with 50 nmol/l). Mean (sd) UVB irradiance at peak summer was significantly higher at the open areas and in the villages than at the inner-city location (340 (45) and 310 (60) v. 250 (50) µW/cm2, P=0·03). CONCLUSIONS: In our population, at latitude 26·8°N, poor skin exposure is a limiting factor in all seasons. During winter, low UVB radiation energy also contributes. Particulate pollution limits UVB irradiance. Vitamin D supplementation during winter may be necessary.
OBJECTIVE: To document the effect of season and environmental pollution on UVB irradiance; and to estimate cutaneous vitamin D synthesis in village women in different seasons. DESIGN: Radiant UVB energy was measured by a spectroradiometer in different seasons and, in April and May, on successive days in open areas at the city outskirts, at a crowded inner-city area and the villages of our participants. Clothing, outdoor activity pattern and serum 25-hydroxycholecalciferol (25(OH)D) levels were documented. SETTING: Rural north India, latitude 26·8°N. SUBJECTS: Pregnant women (n 139, aged 20-40 years). RESULTS: UVB irradiance ranged from 56 µW/cm2 in January to 470 µW/cm2 in June. Proportion of skin exposed was 18·5 % in summer and 9·5 % in winter. Mean (sd) daily duration of sun exposure was 3·2 (0·2) h during winter and 2·1 (0·4) h during summer. Cutaneous vitamin D synthesis was estimated to be 19·25 µg (770 IU) during winter and 37·25 µg (1490 IU) during summer. Mean (sd) serum 25(OH)D was 28 (15) nmol/l during winter (92 % of participants with 50 nmol/l). Mean (sd) UVB irradiance at peak summer was significantly higher at the open areas and in the villages than at the inner-city location (340 (45) and 310 (60) v. 250 (50) µW/cm2, P=0·03). CONCLUSIONS: In our population, at latitude 26·8°N, poor skin exposure is a limiting factor in all seasons. During winter, low UVB radiation energy also contributes. Particulate pollution limits UVB irradiance. Vitamin D supplementation during winter may be necessary.
Entities:
Keywords:
Pollution; Season; Standard erythemal dose; UV radiation energy