Low Vitamin D Levels Are Associated with Elevated Cardiovascular Responses after a Controlled Diesel Exhaust Exposure in Healthy Human Subjects

Cardiovascular disease accounts for over 17 million deaths per year. There is a large body of evidence suggesting that vitamin D deficiency is associated with cardiovascular disease and disease risk factors. In addition, researchers have found that exposures to ambient air pollution – particularly particulate matter (PM) – represent an added and independent risk factor for cardiovascular morbidity and mortality. Therefore, we wanted to assess whether vitamin D levels are associated with a heightened adverse cardiovascular response to diesel exhaust in healthy human subjects. Using a randomized, crossover study design, 13 healthy, young adults were exposed on two separate occasions to 300 µg/m3 diesel exhaust and filtered air under controlled conditions. Before, after, and 18 hrs following each exposure, blood samples were collected. The average vitamin D concentration before clean air exposures was 22.3 ng/mL, and the average vitamin D concentration before diesel exposures was 23.4 ng/mL (paired t-test; p = 0.44). Four participants were considered vitamin D deficient (vitamin D < 20 ng/mL), 7 participants had inadequate vitamin D levels (vitamin D between 21-29 ng/mL), and 2 were vitamin D sufficient (vitamin D > 30 ng/mL). Positive and significant associations were observed between baseline vitamin D concentrations and tPA (β = 6.93, 95% CI = -0.30, 13.57), while a negative and significant association was found with plasminogen (β = -2.84, 95% CI = -5.07, 0.61). At 0 hrs post exposure, there were significant negative associations between baseline vitamin D concentrations and D-dimer (β = 0.02, 95% CI = -0.04, 0.00) and IL-8 (β = -0.03, 95% CI = -0.06, 0.00). Additionally, at 18 hrs post exposure negative associations were found between baseline vitamin D concentrations and PAI-1 (β = -0.03, 95% CI = -0.07, 0.01) and TNF-α (β = -0.03, 95% CI = -0.06, 0.00). This suggests vitamin D deficiency might be associated with elevated cardiovascular responses.