Ambient Air Pollution and Vitamin D Deficiency in Germany: A Model-Based Evidence Synthesis Linking PM₂.₅, Ultraviolet Attenuation, and Deficiency Prevalence

Vitamin D deficiency affects nearly one-third of German adults and worsens dramatically in winter. A key but underexplored driver may be ambient air pollution: fine particulate matter (PM₂. ₅) scatters and absorbs solar UV radiation, reducing the biologically effective dose that reaches the skin and triggers vitamin D synthesis. This preprint presents the first Germany-specific model-based evidence synthesis quantifying this pathway at the federal state (Bundesland) level. Using satellite-derived, cloud-corrected vitamin D–weighted UV data (TEMIS), PM₂. ₅ exposure (APExposeDE v6), and nationally representative vitamin D distributions (RKI/DEGS1, n = 6, 995), we construct a mechanistic framework grounded in the in vivo dose-response equations of Young et al. (2021) — the most rigorous human UV-to-vitamin D calibration available. The model estimates pollution-attributable shifts in population 25 (OH) D and deficiency prevalence across 16 German states (2018–2022), validated against a cross-validation target of −9. 11 nmol/L per 10 μg/m³ PM₂. ₅ from the UK Biobank (n = 448, 337). Results are hypothesis-generating and motivate future individual-level studies linking measured 25 (OH) D to georeferenced pollution and UV exposure in Germany.