[Acute effects of air pollution in Brindisi (Italy): a case-crossover analysis]

To evaluate the association between daily air pollutant concentration and daily data regarding mortality and hospital admissions among residents of Brindisi (Southern Italy) in the years 2003-2006.

The association between the time series of daily mortality (2003-2005) and hospital admissions (2003-2006) and the time series of daily pollutant concentration were analyzed using a case-crossover method and a conditional logistic regression. Bi-directional control periods were selected using a time-stratified approach. Models include mean temperature, relative humidity, influence of epidemics, summer decrease of resident population and holidays as confounders. Specific models with the following variables: cause of death or hospital admission, gender, age and season have been fitted. As hazard periods the following lags have been considered: single lag (from 0 to five) and cumulative lag (lag 0-1 for mortality and 0-3 for hospital admissions).

A total of 1,792 subjects deceased of all natural causes (including cardiovascular and respiratory causes) and 6,925 hospital admissions for acute conditions (cardiac, cerebrovascular and respiratory diseases) were considered. PM10, NO₂ and CO daily pollutant concentration series were examined.

PM10 was associated with mortality from all natural causes (10.36%; 95% CI 1.83-19.61 at lag 0-1). The risk was more pronounced for cardiovascular mortality (14.35%; 95% CI 2.11; 28.07 at lag 1). The association with hospitalization for cerebrovascular diseases was statistically significant for PM10 among females (13.4%; 95% CI 1.7; 26.4 at lag 4) and elderly over 75 years old (13.6%; 95% CI 0.4; 28.6 at lag 4). In specific population groups, increased mortality and hospital admissions have been associated with NO₂.

This study found strong and consistent associations between outdoor air pollution (coming from both industrial emissions and urban traffic) and short-term increases in both mortality and morbidity. Precautionary measures should be taken.