Relationship between Air Pollution and Serum Vitamin D Levels: A Systematic Review and Meta‑Analysis

Background: Elevated levels of atmospheric pollutants might disrupt the metabolism of vitamin D in the skin. Studies showed inconsistent results about the impact of air pollution on the serum vitamin D level. This study aims to systematically review the influence of air pollution on vitamin D levels. Materials and Methods: The Medline database (PubMed), Web of Science, Scopus, and Google Scholar were systematically searched up to the end of July 2020. All observational, English‑language, and human studies that assessed the effect of air pollution on vitamin D levels were included. Results: Among 432 studies, 26 papers were included in the systematic review and five studies in the meta‑analysis. Exposure to air pollution was associated with lower vitamin D levels (pooled mean difference (MD) = −8.04, 95% confidence interval (CI): −10.34, −5.75). There was some evidence of heterogeneity between studies (I² = 91.39%). Conclusion: The findings revealed a reverse correlation between vitamin D levels and air pollution. Air pollutants have an impact on the penetration of solar ultraviolet B (UVB) to the Earth’s surface. Consequently, the occurrence of vitamin D deficiency could be linked to air pollution.