Urban air pollution and emergency room admissions for respiratory symptoms: a case-crossover study in Palermo, Italy

Abstract

Background: Air pollution from vehicular traffic has been associated with respiratory diseases. In Palermo, the largest metropolitan area in Sicily, urban air pollution is mainly addressed to traffic-related pollution because of lack of industrial settlements, and the presence of a temperate climate that contribute to the limited use of domestic heating plants. This study aimed to investigate the association between traffic-related air pollution and emergency room admissions for acute respiratory symptoms.

Methods: From January 2004 through December 2007, air pollutant concentrations and emergency room visits were collected for a case-crossover study conducted in Palermo, Sicily. Risk estimates of short-term exposures to particulate matter and gaseous ambient pollutants including carbon monoxide, nitrogen dioxide, and sulfur dioxide were calculated by using a conditional logistic regression analysis.

Results: Emergency departments provided data on 48,519 visits for respiratory symptoms. Adjusted case-crossover analyses revealed stronger effects in the warm season for the most part of the pollutants considered, with a positive association for PM10 (odds ratio = 1.039, 95% confidence interval: 1.020 - 1.059), SO2 (OR = 1.068, 95% CI: 1.014 - 1.126), nitrogen dioxide (NO2: OR = 1.043, 95% CI: 1.021 - 1.065), and CO (OR = 1.128, 95% CI: 1.074 - 1.184), especially among females (according to an increase of 10 μg/m3 in PM10, NO2, SO2, and 1 mg/m3 in CO exposure). A positive association was observed either in warm or in cold season only for PM10.

Conclusions: Our findings suggest that, in our setting, exposure to ambient levels of air pollution is an important determinant of emergency room (ER) visits for acute respiratory symptoms, particularly during the warm season. ER admittance may be considered a good proxy to evaluate the adverse effects of air pollution on respiratory health.

Figure 1

Map of Palermo (Sicily). Air quality monitoring stations and hospitals.

Figure 2

Odds ratio (OR) for emergency respiratory symptoms calls according to various lag times, Palermo, Sicily, 2005-2007. Lag 0 is for pollutant concentrations averaged on the day of the call, lag 1 is for pollutant concentrations averaged for the previous day of the call, and so on. Associations are expressed as adjusted OR [95% confidence interval (CI)] in relation to an increase of 10 μg/m³ of selected air pollutants (CO: an increase of 1 mg/m³). ORs adjusted for meteo-climatic parameters, and influenza epidemic peaks (see Methods - Statistical analysis).

Figure 3

Single pollutant model results for all respiratory causes according to the same-day exposures, Palermo, Sicily, 2005-2007 (Air pollutants: PM₁₀ and SO₂). Associations are expressed as adjusted odds ratio (OR) [95% confidence interval (CI)] in relation to an increase of 10 μg/m³ of selected air pollutants, according to age groups, sex, and seasons (cold season: October to March, warm season: April to September). ORs adjusted for meteo-climatic parameters, and influenza epidemic peaks (see Methods - Statistical analysis).

Figure 4

Single pollutant model results for all respiratory causes according to the same-day exposures, Palermo, Sicily, 2005-2007 (Air pollutants: CO and NO₂). Associations are expressed as adjusted odds ratio (OR) [95% confidence interval (CI)] in relation to an increase of 10 μg/m³ of selected air pollutants (CO: an increase of 1 mg/m³), according to age groups, sex, and seasons (cold season: October to March, warm season: April to September). ORs adjusted for meteo-climatic parameters, and influenza epidemic peaks (see Methods - Statistical analysis).