Air pollution and venous thrombosis: a meta-analysis

Exposure to air pollution has been linked to cardiovascular and respiratory disorders. However, the effect of air pollution on venous thrombotic disorders is uncertain. We performed a meta-analysis to assess the association between air pollution and venous thrombosis. PubMed, Embase, EBM Reviews, Healthstar, Global Health, Nursing Database, and Web of Science were searched for citations on air pollutants (carbon monoxide, sulfur dioxide, nitrogen dioxide, ozone, and particulate matters) and venous thrombosis. Using a random-effects model, overall risk estimates were derived for each increment of 10 μg/m(3) of pollutant concentration. Of the 485 in-depth reviewed studies, 8 citations, involving approximately 700,000 events, fulfilled the inclusion criteria. All the main air pollutants analyzed were not associated with an increased risk of venous thrombosis (OR = 1.005, 95% CI = 0.998-1.012 for PM2.5; OR = 0.995, 95% CI = 0.984-1.007 for PM10; OR = 1.006, 95% CI = 0.994-1.019 for NO2). Based on exposure period and thrombosis location, additional subgroup analyses provided results comparable with those of the overall analyses. There was no evidence of publication bias. Therefore, this meta analysis does not suggest the possible role of air pollution as risk factor for venous thrombosis in general population.