Access rate to the emergency department for venous thromboembolism in relationship with coarse and fine particulate matter air pollution

Abstract

Particulate matter (PM) air pollution has been associated with cardiovascular and respiratory disease. Recent studies have proposed also a link with venous thromboembolism (VTE) risk. This study was aimed to evaluate the possible influence of air pollution-related changes on the daily flux of patients referring to the Emergency Department (ED) for VTE, dissecting the different effects of coarse and fine PM. From July 1(st), 2007, to June 30(th), 2009, data about ED accesses for VTE and about daily concentrations of PM air pollution in Verona district (Italy) were collected. Coarse PM (PM(10-2.5)) was calculated by subtracting the finest PM(2.5) from the whole PM(10). During the index period a total of 302 accesses for VTE were observed (135 males and 167 females; mean age 68.3 ± 16.7 years). In multiple regression models adjusted for other atmospheric parameters PM(10-2.5), but not PM(2.5), concentrations were positively correlated with VTE (beta-coefficient = 0.237; P = 0.020). During the days with high levels of PM(10-2.5) (≥ 75(th) percentile) there was an increased risk of ED accesses for VTE (OR 1.69 with 95%CI 1.13-2.53). By analysing days of exposure using distributed lag non-linear models, the increase of VTE risk was limited to PM(10-2.5) peaks in the short-term period. Consistently with these results, in another cohort of subjects without active thrombosis (n = 102) an inverse correlation between PM(10-2.5) and prothrombin time was found (R = -0.247; P = 0.012). Our results suggest that short-time exposure to high concentrations of PM(10-2.5) may favour an increased rate of ED accesses for VTE through the induction of a prothrombotic state.

Figure 1. Seasonal trend of total, fine, and coarse particulate matter (PM₁₀, PM_2.5, and PM_10-2.5) concentrations during the study period.

In Figure 1A, PM₁₀ levels are represented by the orange line and the area under the curve is divided in the 2 components, PM_2.5 represented by the green area and PM_10-2.5 represented by the ochre yellow area. In Figure 1B, the seasonal trend of PM_10-2.5 concentrations is separately represented and related with data of daily admissions for venous thromboembolism (VTE). The dashed line represents the PM_10-2.5 75^th percentile, at 19 µg/m³.

Figure 2. Coarse particulate matter (PM_10-2.5) and daily admissions to the Emergency Department for venous thromboembolism (VTE).

Data are presented as mean level of PM_10-2.5 concentration (Figure 2A) and prevalence of days with high PM_10-2.5 concentration, defined as higher than the 75^th percentile – 19 mcg/m³ (Figure 2B), according to the number of daily admissions to the Emergency Department for VTE.

Figure 3. Association between daily hospital referral for venous thromboembolism (VTE) and coarse particulate matter (PM_10-2.5) concentration at different time-lags.

The association was estimated by using distributed lag non-linear models with VTE risk as outcome and time-lags expressed as the number of previous days. Only the current-day (lag 0) PM_2.5-10 levels presented a significant association with VTE risk.