A leading factor influencing the extent of solar UVB reaching the Earth’s surface is considered as Air pollution. Observational and prospective studies in different geographic latitudes with different populations proved that atmospheric pollution may play a vital independent role in the growth of Vitamin D Deficiency. Absorption of UVB radiation and the decrease in the amount of photons reaching ground level can efficiently be a result of tropospheric ozone. The extent of solar UVB that reached Earth’s surface is inversely related to the level of pollution, and this theory was proved. The frequency of D hypovitaminosis among urban inhabitants can be more than twice higher as compared to the rural inhabitants, because industrial areas are those of the highest concentration of air pollution.
A recent study that ties Vitamin D with high BP has severe implications for India, where every fifth grown-up has hypertension. Besides modern lifestyles that cause children and adults to spend most of their time indoors, doctors say the quality of sunlight in smog-hit cities may also play a role in causing the deficiency.
According to a report featured in the Times of India, researcher VimalKarani of University College, London, went through 35 studies which spanned over 1.5 lakh people across North America and Europe, and found that for every 10% increase in 25(OH) D concentrations, the risk of developing hypertension decreased by 8.1%. A prehormone, 25-hydroxyvitamin D (25(OH) D or calcidiol, is produced in the liver when Vitamin D3 is synthesized (a blood test to determine its levels is also an indicator of Vit D levels).
According to a study titled, The impact of atmospheric pollution on vitamin D status of infants and toddlers in Delhi, India by Agarwal KS and others in 2002, compared to those living in the less polluted areas, children living in the highly polluted parts of Delhi, with higher levels of ambient air pollution have been shown to be at a higher risk of developing Vitamin D-dependent rickets. Under the same study, despite similar types of housing, the mean serum concentration of 25 (OH) D3 compared to those living in the less polluted areas of the city was significantly lower. The amount of UVB light reaching the ground level was correlated with the intensity of air pollution that in turn correlated to the frequency of Vitamin D Deficiency. The differences in the Vitamin D status of the children cannot be explained by their different dietary habits, because none of the children included in the study used any Vitamin D supplementation or ate Vitamin D stimulated food. However, the time which each individual spent on exposition to sunlight, that seems to be a chief limitation of this work, was not collected by the authors.
For many years the problem of Vitamin D insufficiency has been underestimated, associated only with calcium/phosphorus metabolism and regarded as an area of interest reserved only for pediatricians or orthopedists. However, the last years brought a number of epidemiological studies revealing the unexpected connection between the Vitamin D hypovitaminosis and prevalence of several diseases that have forced the scientist to revise their opinions on the mechanism of Vitamin D action and its role in the maintenance of body homeostasis.