title: Sun exposure, UV irradiance and serum 25-hydroxycholecalciferol in pregnant women in rural north 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.
  
  
  METHODS
  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.
  
  
  METHODS
  Rural north India, latitude 26·8°N.
  
  
  METHODS
  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.
authors.affiliation: 1Department of Endocrinology,Sanjay Gandhi Postgraduate Institute of Medical Sciences,Lucknow 226014,Uttar Pradesh,India.
authors.forename: Siddhnath
authors.initials: S
authors.lastname: Sudhanshu
authors.affiliation: 2National Institute of Immunology,New Delhi,India.
authors.forename: Pramod
authors.initials: P
authors.lastname: Upadhyay
authors.affiliation: 3Max Hospital,New Delhi,India.
authors.forename: Monashish
authors.initials: M
authors.lastname: Sahu
authors.affiliation: 4Department of Microbiology,Government Medical College,Haldwani,Uttarakhand,India.
authors.forename: Vinita
authors.initials: V
authors.lastname: Rawat
authors.affiliation: 1Department of Endocrinology,Sanjay Gandhi Postgraduate Institute of Medical Sciences,Lucknow 226014,Uttar Pradesh,India.
authors.forename: Vijayalakshmi
authors.initials: V
authors.lastname: Bhatia
mesh_terms: D015652:25-Hydroxyvitamin D 2 / Q000097:blood*; D000328:Adult; D004787:Environmental Pollution / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D007194:India; D011247:Pregnancy; D012424:Rural Population / Q000706:statistics & numerical data*; D012621:Seasons; D013472:Sunlight; D014466:Ultraviolet Rays; D055815:Young Adult
chemical_list: D015652:25-Hydroxyvitamin D 2
keywords: Pollution; Season; Standard erythemal dose; UV radiation energy