Farhad Hosseinpanah, Sima Hashemi pour, Motahare Heibatollahi, Nilufar Moghbel, Saeed Asef zade and Fereidoun Azizi
BMC Public Health 2010, 10:519doi:10.1186/1471-2458-10-519
Published: 29 August 2010
Background Inadequate radiation or insufficient cutaneous absorption of UVB is one of the cardinal causes of vitamin D deficiency. The aim of this study is to determine whether air pollution and low ground level of ultra-violet B light (UVB; 290-315) can deteriorate the body vitamin D status in healthy women.
Methods In this cross sectional study 200, free-living, housewives, aged between 20 to 55 years, from Tehran (high polluted area) and Ghazvin (low polluted area) were included. The Tehranian women were selected randomly from participants of the Tehran Lipid and Glucose Study (TLGS) and the Ghazvinian females from patients who came to public health centers. Participants were excluded for disease and drugs which affect vitamin D status and also if they were pregnant or breast feeding. We measured the ground level of UVB using a Haze meter as a surrogate of air pollution. In order to calculate the adjusted mean difference of 25-OH-D, ANCOVA analysis was used. Moreover, Binary logistic regression model was developed to determine the odds of living in Tehran for having serum 25-OH-D less than 20 ng/ml.
Results The mean+/- SD of serum 25-OH-D was significantly higher in Ghazvinian women (18+/-11 vs. 13+/-7), P-value < 001). The prevalence of 25-OH-D less than 10 ng/ml, and 25-OH-D between 10 and 20 ng/ml were higher in Tehranian group (36% and 54% vs. 31% and 32 % in respectively). Secondary hyperparathyroidism was also significantly higher in Tehranian women (47% vs. 32%). In ANCOVA analysis, after adjustment, the mean of 25-OH-D in the Ghazvinian group was still statistically significantly higher than Tehranians (13 vs. 17 ng/ml P-value = 0.04). In addition, in binary logistic model, the odd of living in Tehran for having serum 25-OH-D less than 20 ng/ml was 5.22 (95% confidence interval 2.2-12.2, P-value < 0.001).
Conclusion We found that living in a polluted area plays a significant independent role in vitamin D deficiency and hence, residence can be one of the main reasons of vitamin D status of the women.
This study has limitations that are mainly due to problems related to our equipment.
- First, our hypothesis was that the lower ground levels of UVB in more polluted area are mainly due to atmospherics' pollutant aerosols but some other parameters may also contribute in it. *Second, it was impossible for us to determine the main chemical particles that absorb and decrease UVB radiations.
- Third, because of limited number of centers that measured ground levels of UVB, we were unable to analysis the magnitude of UVB as a parameter and just defined the city of living as a surrogate of the ground level of UVB.
- Fourth, we did not calculate sun exposure index. But, it seems that due to the facts that Iranian women clothing styles have no significant variations and all of the women in this study were housewives, there is no significant differences between these two place sun exposure indexes. We defined simple questions for housing status, time spent outdoor, and the usage pattern of sunscreen instead of sun exposure index.
- Fifths, it was impossible to measure the blood levels of specific bone markers.
- Last but not least, it is important to mention that there is an increase in solar UVB doses from a difference in surface elevation above the sea level. The amount seems to be between 20% per 1000 m at the elevation of the two cities . The elevation difference between the two cities is 640 m, implying a difference of 12%. This difference contributes, in part to differences in serum 25-OH-D levels (about 30% percent of mentioned differences between Tehran and Ghazvin 25-OH-D may be due to surface elevation differences).
It would also affect the fraction of the populations below specified 25-OH-D levels. However, ground level of UVB was significantly higher in Ghazvin as compared with Tehran (mean (SE), 0.31(0.07) and 0.16(0.03) W/m 2 respectively, P-value = 0.003).
_This means that at least 70% percent of serum vitamin D difference is due to air pollution.__ Despite these limitations, our study does have advantages over previous studies. Our strengths are: to define objectively the amount of air pollution, we measured the magnitude of UVB that reached the earth surface by the Haze meter instrument. In addition, daily information on dietary intake of vitamin D and duration of sun exposure, as two main determinant of vitamin D storage, were also considered. Besides these advantages, we recruited our samples from participants of a large population based study in Tehran and from public health centers in Ghazvin.
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The article does not mention burka - wonder if they are worn more by women in urban than rural areas
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