Seasonal variations in vitamin D status in Bangladesh: a preliminary look at the potential role of aerosol pollution

Abstract

Vitamin D deficiency is common in South Asia, but the causes are unclear. Particulate air pollution interferes with ultraviolet (UV) irradiation of the earth surface, but the effect of UV‐absorbing aerosols on vitamin D status is unknown. Associations among vitamin D status (serum 25‐hydroxyvitamin D, [25(OH)D]), UV radiation exposure and UV‐absorbing aerosols in Dhaka were explored based on observations of 34 non‐pregnant and 13 pregnant women in July‐Oct 2009, and 28 pregnant women in Feb 2010 (N=75). Average [25(OH)D] was lower in winter vs. summer/fall; among the pregnant women, mean [25(OH)D] was 12 nmol/L lower in Feb vs. Aug‐Oct (95% CI, 1 – 22 nmol/L). Seasonal differences in [25(OH)D] could be largely explained by variations in personal UV exposure estimated using polysulphone (PS) badges worn on the shoulder, averaged over 2–3 days within ~2 months of [25(OH)D] assessment (N=72). UV exposure by PS dosimetry and [25(OH)D] were both inversely associated with the estimated UV aerosol index (UVAI) for Dhaka, based on satellite‐generated data downloaded from an on‐line NASA database (OMI/Aura). The UVAI peaked in early spring (before the monsoon season), when average UV exposures by PS dosimetry were lowest. These preliminary observations suggest that UV‐absorbing aerosols may have important effects on UV‐induced cutaneous vitamin D synthesis in South Asia and merit further research.Grant Funding Source: Center for Global Health, Johns Hopkins University; Department of International Health, Johns Hopkins Bloomberg School of Public Health