Could pulmonary thromboembolism be associated with air pollution ?

Pulmonary thromboembolism (PTE) develops in patients with and without clear predisposing factors and sometimes tends to occur more frequently at certain time periods. This temporal clustering may be related to air pollution, particularly in individuals without any known risk factors. There are contradictory reports of possible associations of PTE with increased exposure to certain pollutants, which lead to pulmonary and systemic inflammation. This study aimed to determine whether exposure to air pollution could be associated with the development of PTE. All PTE patients diagnosed at a single tertiary care center for a two-year period were retrospectively examined. Data from the website of the national agency for air quality were retrieved for the day and the four-week period prior to the diagnosis of PTE for the related locations. These included levels of PM10, SO2, NO2 and CO. Demographic data, predisposing factors, comorbidities, severity of the embolism and clinical outcomes were noted. A total of 195 consecutive patients (56.4% female, mean age 65.9±17.2 y) were included in the study. Of these, 72.3% had predisposing factors, 27.2% had subsegmental, 56.5% segmental and/or lobar, 16.3% massive or submassive emboli. There was no relationship between the PTE severity and the levels of the air pollutants during the preceding day or four weeks. There was also no association between the presence/absence of a predisposing factor and pollutant levels except that the mean CO levels were higher during the preceding day in patients with unprovoked PTE (734 vs 475 µg/m³, p=0.005). PTE does not seem to be related to air pollution. The association of increased CO levels with unprovoked PTE may deserve further research.