Ozone decreases Vitamin D: 1) Decreases time outdoors, 2) Decreases UVB
Claude AI April 2026
Ground-level ozone absorbs UVB by the same Hartley/Huggins-band physics that makes the stratospheric layer protective — tropospheric O₃ is just a smaller column in the same path. So ozone pollution hits vitamin D synthesis twice: avoidance behavior and reduced surface UVB for anyone who does go outside.
Magnitudes from the literature:
Near urban emission sources, surface UV irradiance is attenuated by up to ~20% by O₃, NO₂, and SO₂ in the lower troposphere.
NO₂ alone accounts for ~2–3% average UV-B attenuation, up to 6% routinely, and 11–14% during extreme pollution episodes (e.g., 2002 Moscow fires) — so in smoggy/ozone-heavy days the co-pollutants compound the effect.
Ozone column at a given location can swing ~20% day-to-day depending on pollution and wind, which means surface UVB is meaningfully variable even before cloud cover is considered.
The Montreal Protocol assessments explicitly note that the small observed UV changes over recent decades at mid-latitudes were driven substantially by aerosols and tropospheric pollution controls, not just stratospheric ozone recovery.
Coal plants also emit SO2, particulates, and mercury, but those are separate issues from ozone.
- Ozone formation is downwind and delayed — plumes can generate peak ozone 50–200+ miles from the stack, hours later.
- This is why EPA's Cross-State Air Pollution Rule and NOx Budget Trading Programs specifically target power-plant NOx during the ozone season (May–September).
- Note 25% of Native Americans live within 50 miles of a coal-burning power plant.
Hyperlinked references are online
Urban Tropospheric Ozone Increases the Prevalence of Vitamin D Deficiency among Belgian Postmenopausal Women with Outdoor Activities during Summer - 2008
The Journal of Clinical Endocrinology & Metabolism Vol. 93, No. 10 3893-3899
Daniel-Henri Manicourt and Jean-Pierre Devogelaer
Context: By absorbing sunlight UVB and thereby reducing cutaneous vitamin D photosynthesis, ozone, a common urban pollutant, could cause hypovitaminosis D.
Objectives: The objective of the study was to establish the characteristics and percentage of subjects with serum 25-hydroxyvitamin D [25(OH)D] less than 75 nmol/liter among postmenopausal women engaging in outdoor activities in either Brussels or the countryside.
Design/Setting: This was a cross-sectional study conducted in a university research hospital.
Patients/Methods: Among 249 women consulting for either shoulder tendonitis or lumbar spine osteoarthritis , 121 free of conditions and drugs affecting bone and calcium metabolism completed two food-frequency questionnaires within 15 d and we selected the 85 subjects with retest scores within the ± 15% of test scores. Other parameters included sun exposure index (SEI) , PTH levels, and femoral neck T-score.
Results: Urban residents (n = 38) and rural residents (n = 47) did not differ in mean ages, body mass indices, and vitamin D intakes. When compared with rural inhabitants, urban inhabitants were exposed to ozone levels 3 times higher , and despite a higher mean SEI (113 vs. 87; P < 0.001), they had a higher prevalence of 25(OH)D less than 75 nmol/liter (84 vs. 38%). After adjusting for SEI, 25(OH)D was 2-fold higher in rural residents, and after adjusting for 25(OH)D, SEI was 3-fold higher in urban residents . Femoral neck T-scores correlated positively with 25(OH)D and negatively with PTH levels.
Conclusions: Air pollution may be a neglected risk factor for hypovitaminosis D, which is known to compromise several health outcomes. As long as 25(OH)D is greater than 75 nmol/liter, calcium intakes greater than 17.5 mmol/d are unnecessary to prevent elevations in PTH levels.
There could be other factors at work, such as more stress in the city, more surgery in the city, etc.
Summary: Urban patients had 3X more ozone and had a higher level of sun exposure than rural.
Yet 83% of the urban patients had vitamin D levels less than 30 ng, vs 38% of the rural patients.
More urban pollution ==> more ozone ==> less UVB reaching ground level ==> lower vitamin D production in skin.
Study had been cited 150 times as of April 2019