Expusure to air pollutants during pregnancy and outcome at birth. An epidemiological study in Lombardy 2004-2008.

Our study is the first epidemiological research that investigates the effect of ambient air pollution in Italy or in other Southern European countries. We used existing air pollution and birth records data. This allowed us for a very large, population based study, not subject to selection bias, and conducted for a long period of time (5 years) in one of the most polluted European Region. We observed only a mild effect of PM10 measured during the entire pregnancy period on birthweight (-5 grams for a 10 ??/m3 increase). The negative effect on bithweight was not concentrated in one specific trimester (although more pronounced during the last three months). The clinical relevance of the observed effect is doubtful and is also curbed by the fact that we did not observe any PM10 exposure- related increased risk in SGA incidence. Our results, as the ones of the most of the recent published study all around the world, seems to rule out a more than moderate effect of air pollution on baby growth and gestational duration, but we confirm the evidence of a small adverse effect of PM on birthweight. As described in details in the systematic review, environmental studies based on monitoring station data and on routinely collected birth records although very efficient in collecting large birth cohorts, have shown important limits, and is not possible to dodge a residual misclassification of exposure and inadequate collection of maternal characteristics. Therefore it is not easy to understand if the small size of the observed effect is a consequence of these important limitations which most likely led to an attenuated estimate of the true effect of air pollution. However, given the number of exposed people, if these small effects are indeed causal, the public health impact could be considerable. Additional studies in that field would thus be warranted, but there is a strong need of innovative approach that combine different exposure estimates methods (possibly using also personal monitoring), and that move forward in determining different components of air pollution and possible biomarkers of exposure to delineate the biological mechanism of such an effect.