Causal inference methods in environmental epidemiology: different approaches to evaluate the health effects of industrial air pollution.

This study aims at implementing different causal inference approaches for the first time in a longitudinal cohort analysis with a continuous exposure, to assess the causal effect of industrial air pollution on health. A first review of the literature on the addressed causal inference methods is conducted, focusing on the main assumptions and suggested applications. Then the main longitudinal study, from which the causal inference methods originate, is described. A standard time-to-event analysis is performed to assess the relationship between exposure to air pollution (PM10 and SO2 from industrial origin) and mortality, as well as morbidity, in the cohort of residents around a large steel plant in the Taranto area (Apulia region, Italy). The Difference-in difference (DID) approach as well as three methods using the generalized propensity score (Propensity Function-PF of Imai and van Dyk, the Dose-response Function DRF by Hirano and Imbens, and the Robins’ Importance sampling-RIS using the GPS) were implemented in a Cox Proportional Hazard model for mortality. The main study demonstrated a negative effect of exposure to industrial air pollution on mortality and morbidity, after controlling for occupation, age, time period, and socioeconomic position index. The health effects were confirmed in all the causal approaches applied to the cohort, and the concentration-response curves showed increasing risk of natural and cause-specific mortality for higher levels of PM10 and SO2. We conclude that the health effects estimated are causal and that the adjustment for socioeconomic index already takes into account other, not measured, individual factors

Inquinamento atmosferico e ricoveri ospedalieri urgenti in 25 citt? italiane: risultati del progetto EpiAir2 Air pollution and urgent hospital admissions in 25 Italian cities: results from the EpiAir2 project

OBJECTIVE: to evaluate the relationship between air pollution and hospital admissions in 25 Italian cities that took part in the EpiAir (Epidemiological surveillance of air pollution effects among Italian cities) project. DESIGN: study of time series with case-crossover methodology, with adjustment for meteorological and time-dependent variables. The association air pollution hospitalisation was analyzed in each of the 25 cities involved in the study; the overall estimates of effect were obtained subsequently by means of a meta-analysis. The pollutants considered were PM10, PM2.5 (in 13 cities only), NO2 and ozone (O3); this last pollutant restricted to the summer season (April-September). SETTING AND PARTICIPANTS: the study has analyzed 2,246,448 urgent hospital admissions for non-accidental diseases in 25 Italian cities during the period 2006- 2010; 10 out of 25 cities took part also in the first phase of the project (2001-2005). MAIN OUTCOME MEASURES: urgent hospital admissions for cardiac, cerebrovascular and respiratory diseases, for all age groups, were considered. The respiratory hospital admissions were analysed also for the 0-14-year subgroup. Percentage increases risk of hospitalization associated with increments of 10 μg/m3 and interquartile range (IQR) of the concentration of each pollutant were calculated. RESULTS: reported results were related to an increment of 10 μg/m3 of air pollutant. The percent increase for PM10 for cardiac causes was 0.34% at lag 0 (95%CI 0.04-0.63), for respiratory causes 0.75%at lag 0-5 (95%CI 0.25-1.25). For PM2.5, the percent increase for respiratory causes was 1.23% at lag 0- 5 (95%CI 0.58-1.88). For NO2, the percent increase for cardiac causes was 0.57%at lag 0 (95%CI 0.13-1.02); 1.29% at lag 0-5 (95%CI 0.52-2.06) for respiratory causes. Ozone (O3) did not turned out to be positively associated neither with cardiac nor with respiratory causes as noted in the previous period (2001-2005). CONCLUSION: the results of the study confirm an association between PM10, PM2.5, and NO2 on hospital admissions among 25 Italian cities. No positive associations for ozone was noted in this period.OBIETTIVO: valutare la relazione tra inquinamento atmosferico e ricoveri ospedalieri nelle citt? italiane partecipanti alla seconda fase del progetto EpiAir (Sorveglianza epidemiologica dell\u27inquinamento atmosferico: valutazione dei rischi e degli impatti nelle citt? italiane). DISEGNO: studio di serie temporali con metodologia case-crossover, con aggiustamento per i fattori temporali e meteorologici rilevanti. L\u27associazione inquinamento atmosferico- ospedalizzazioni ? stata analizzata in ciascuna delle 25 citt? in studio, le stime complessive di effetto sono state ottenute successivamente mediante una metanalisi. Gli inquinanti considerati sono stati il particolato (PM10), il biossido di azoto (NO2) e l\u27ozono (O3), quest\u27ultimo limitatamente al semestre estivo (da aprile a settembre). In 13 citt? in cui i dati erano disponibili ? stata analizzata anche la frazione fine del particolato (PM2.5). SETTING E PARTECIPANTI: lo studio ha esaminato 2.246.448 ricoveri ospedalieri urgenti per cause naturali di pazienti residenti e ricoverati, nel periodo 2006-2010, in 25 citt? italiane, di cui 10 gi? partecipanti alla prima fase del progetto EpiAir (2001-2005). PRINCIPALIMISURE DI OUTCOME: sono stati considerati i ricoveri ospedalieri urgenti per malattie cardiache, cerebrovascolari e respiratorie per tutte le fasce di et?. I ricoveri per cause respiratorie sono stati analizzati separatamente anche per la fascia di et? 0-14 anni. L\u27esposizione ? stata valutata per incremento sia di 10 μg/m3 sia pari all\u27intervallo interquartile (IQR) della concentrazione di ciascun inquinante. RISULTATI: considerando un incremento di 10 μg/m3 per inquinante, per il PM10 ? stato osservato un incremento percentuale di rischio per patologie cardiache dello 0,34%a lag 0 (IC95% 0,04-0,63), e per patologie respiratorie dello 0,75% a lag 0-5 (IC95% 0,25-1,25). Per il PM2.5 l\u27incremento percentuale di rischio per patologie respiratorie ? risultato dell\u271,23%a lag 0-5 (IC95%0,58-1,88). Per l\u27NO2 la stima di effetto per patologie cardiache ? risultata dello 0,57% a lag 0 (IC95% 0,13-1,02), e per patologie respiratorie dell\u271,29% a lag 0-5 (IC95% 0,52-2,06). L\u27ozono non ? risultato positivamente associato n? alle patologie cardiache n? a quelle respiratorie (a differenza del periodo 2001-2005). CONCLUSIONE: i risultati dello studio confermano l\u27effetto a breve termine dell\u27inquinamento atmosferico da PM10, PM2.5 e NO2 sulla morbosit?, in particolare respiratoria, nelle citt? italiane. Non sono state rilevate associazioni positive per l\u27O3

Saharan dust and the association between particulate matter and daily hospitalisations in Rome, Italy

Introduction Outbreaks of Saharan dust have been shown to exacerbate the effect of particulate matter (PM) on mortality. Their role on PM-morbidity association is less clear. This study aims to evaluate the effect of Saharan dust on the PM-hospitalisations association in Rome, Italy. Methods We studied residents hospitalised in Rome between 2001 and 2004 and performed a time-series analysis to explore the effects of PM2.5, PM2.5-10 and PM10 on cardiac, cerebrovascular and respiratory emergency hospitalisations, respectively. Saharan dust days were identified by combining Light Detection and Ranging observations and analyses from operational models. We tested a dust-PM interaction to evaluate the hypothesis that the PM effect on hospitalisations would be enhanced on dust days. Results We studied 77 354, 26 557 and 31 620 hospitalisations for cardiac, cerebrovascular and respiratory diseases, respectively, providing effect estimates per IQR. PM2.5-10 was associated with cardiac diseases (3.93%; 95% CI 1.58 to 6.34). PM 10 was associated with cardiac (3.37%; 95% CI 1.11 to 5.68), cerebrovascular (2.64%; 95% CI 0.06 to 5.29) and respiratory diseases (3.59%: 95% CI 0.18 to 7.12). No effect of PM2.5 was detected. Saharan dust modified the effect of the PM2.5-10 on respiratory hospitalisations, higher during dust days compared with dust-free days (14.63% vs -0.32%; p value of interaction=0.006). Saharan dust also increased the effect of PM10 on cerebrovascular diseases (5.04% vs 0.90%, p value of interaction=0.143). Discussion A clear enhanced effect of PM2.5-10 on respiratory diseases and of PM10 on cerebrovascular diseases emerged during Saharan dust outbreaks

Does chronic exposure to high levels of nitrogen dioxide exacerbate the short-term effects of airborne particles?

The short-term effects of PM10 on mortality and whether long-term exposure to NO2 modifies this association were investigated among 124,432 35+ year-old participants who died in Rome between 2001 and 2010 and maintained the same address for at least 5 years before death. Modification of PM10-related mortality by long-term NO2 exposure was determined by two-way interaction, while a three-way interaction was employed to assess effect modification of high NO2 levels in population groups defined by socio-demographic position and pre-existing diseases. An overall increase in mortality for each 10 \uce\ubcg/cu m increase in PM10 was observed. Short-term PM10-related mortality increased among people exposed to both high and low NO10 levels, but a clear effect modification was not detected. However, effect modifications of short-term PM10-related mortality were observed among those exposed to long-term NO2 for people over the age of 85-years, for those with pre-existing arrhythmias, and for those with pre-existing chronic obstructive pulmonary disease

Association between short-term exposure to PM2.5 and PM10 and mortality in susceptible subgroups: A multisite case-crossover analysis of individual effect modifiers

We performed a multisite study to evaluate demographic and clinical conditions as potential modifiers of the particulate matter (PM).mortality association. We selected 228,619 natural deaths of elderly persons (ages .65 years) that occurred in 12 Italian cities during the period 2006.2010. Individual data on causes of death, age, sex, location of death, and preexisting chronic and acute conditions from the previous 5 years' hospitalizations were collected. City-specific conditional logistic regression models were applied within the case-crossover "timestratified" framework, followed by random-effects meta-analysis. Particulate matter less than or equal to 2.5 \uce\ubcm in aerodynamic diameter (PM2.5) and particulate matter less than or equal to 10 \uce\ubcm in aerodynamic diameter (PM10) were positively associated with natural mortality (1.05% and 0.74% increases in mortality risk for increments of 10 \uce\ubcg/m3 and 14.4 \uce\ubcg/m3, respectively), with greater effects being seen among older people, those dying out-of-hospital or during the warm season, and those affected by 2 or more chronic diseases. Limited associations were found among persons with no previous hospital admissions. Diabetes (1.98%, 95% confidence interval (CI): 0.54, 3.44) and cardiac arrhythmia (1.65%, 95% CI: 0.37, 2.95) increased risk of PM2.5- related mortality, while heart conduction disorders increased risk of mortality related to both PM2.5 (4.22%, 95% CI: 0.15, 8.46) and PM10 (4.19%, 95% CI: 0.38, 8.14). Among acute conditions, recent hospital discharge for heart failure modified the PM10-mortality association. The study found increases in natural mortality from PM exposure among people with chronic morbidity; diabetes and cardiac disorders were the main susceptibility factors

[Air pollution and urgent hospital admissions in 25 Italian cities: results from the EpiAir2 project]

OBJECTIVE: to evaluate the relationship between air pollution and hospital admissions in 25 Italian cities that took part in the EpiAir (Epidemiological surveillance of air pollution effects among Italian cities) project. DESIGN: study of time series with case-crossover methodology, with adjustment for meteorological and time-dependent variables. The association air pollution hospitalisation was analyzed in each of the 25 cities involved in the study; the overall estimates of effect were obtained subsequently by means of a meta-analysis. The pollutants considered were PM10, PM2.5 (in 13 cities only), NO2 and ozone (O3); this last pollutant restricted to the summer season (April-September). SETTING AND PARTICIPANTS: the study has analyzed 2,246,448 urgent hospital admissions for non-accidental diseases in 25 Italian cities during the period 2006- 2010; 10 out of 25 cities took part also in the first phase of the project (2001-2005). MAIN OUTCOME MEASURES: urgent hospital admissions for cardiac, cerebrovascular and respiratory diseases, for all age groups, were considered. The respiratory hospital admissions were analysed also for the 0-14-year subgroup. Percentage increases risk of hospitalization associated with increments of 10 \ub5g/m(3) and interquartile range (IQR) of the concentration of each pollutant were calculated. RESULTS: reported results were related to an increment of 10 \ub5g/m(3) of air pollutant. The percent increase for PM10 for cardiac causes was 0.34% at lag 0 (95%CI 0.04-0.63), for respiratory causes 0.75% at lag 0-5 (95%CI 0.25-1.25). For PM2.5, the percent increase for respiratory causes was 1.23% at lag 0- 5 (95%CI 0.58-1.88). For NO2, the percent increase for cardiac causes was 0.57% at lag 0 (95%CI 0.13-1.02); 1.29% at lag 0-5 (95%CI 0.52-2.06) for respiratory causes. Ozone (O3) did not turned out to be positively associated neither with cardiac nor with respiratory causes as noted in the previous period (2001-2005). CONCLUSION: the results of the study confirm an association between PM10, PM2.5, and NO2 on hospital admissions among 25 Italian cities. No positive associations for ozone was noted in this period

[Air pollution and mortality in twenty-five Italian cities: results of the EpiAir2 Project]

this study aims at presenting the results from the Italian EpiaAir2 Project on the short-term effects of air pollution on adult population (35+ years old) in 25 Italian cities

Short-term effects of particulate matter on mortality during forest fires in Southern Europe: Results of the MED-PARTICLES project

Background: An association between occurrence of wildfires and mortality in the exposed population has been observed in several studies with controversial results for cause-specific mortality. In the Mediterranean area, forest fires usually occur during spring-summer, they overlap with Saharan outbreaks, are associated with increased temperature and their health effects are probably due to an increase in particulate matter. Aim and methods: We analysed the effects of wildfires and particulate matter (PM10) on mortality in 10 southern European cities in Spain, France, Italy and Greece (2003-2010), using satellite data for exposure assessment and Poisson regression models, simulating a case-crossover approach. Results: We found that smoky days were associated with increased cardiovascular mortality (lag 0-5, 6.29%, 95% CIs 1.00 to 11.85). When the effect of PM10 (per 10 mg/m3) was evaluated, there was an increase in natural mortality (0.49%), cardiovascular mortality (0.65%) and respiratory mortality (2.13%) on smoke-free days, but PM10-related mortality was higher on smoky days (natural mortality up to 1.10% and respiratory mortality up to 3.90%) with a suggestion of effect modification for cardiovascular mortality (3.42%, p value for effect modification 0.055), controlling for Saharan dust advections. Conclusions: Smoke is associated with increased cardiovascular mortality in urban residents, and PM10 on smoky days has a larger effect on cardiovascular and respiratory mortality than on other days

Desert dust outbreaks in southern Europe: contribution to daily PM10 concentrations and short-term associations with mortality and hospital admissions

BACKGROUND: Evidence on the association between short-term exposure to desert dust and health outcomes is controversial. OBJECTIVES: We aimed to estimate the short-term effects of particulate matter ≤ 10 μm (PM10) on mortality and hospital admissions in 13 Southern European cities, distinguishing between PM10 originating from the desert and from other sources. METHODS: We identified desert dust advection days in multiple Mediterranean areas for 2001-2010 by combining modeling tools, back-trajectories, and satellite data. For each advection day, we estimated PM10 concentrations originating from desert, and computed PM10 from other sources by difference. We fitted city-specific Poisson regression models to estimate the association between PM from different sources (desert and non-desert) and daily mortality and emergency hospitalizations. Finally, we pooled city-specific results in a random-effects meta-analysis. RESULTS: On average, 15% of days were affected by desert dust at ground level (desert PM10 > 0 μg/m3). Most episodes occurred in spring-summer, with increasing gradient of both frequency and intensity north-south and west-east of the Mediterranean basin. We found significant associations of both PM10 concentrations with mortality. Increases of 10 μg/m3 in non-desert and desert PM10 (lag 0-1 days) were associated with increases in natural mortality of 0.55% (95% CI: 0.24, 0.87%) and 0.65% (95% CI: 0.24, 1.06%), respectively. Similar associations were estimated for cardio-respiratory mortality and hospital admissions. CONCLUSIONS: PM10 originating from the desert was positively associated with mortality and hospitalizations in Southern Europe. Policy measures should aim at reducing population exposure to anthropogenic airborne particles even in areas with large contribution from desert dust advections