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Respiratory effects of sulphur dioxide: a hierarchical multicity analysis in the APHEA 2 study

J Sunyer¹, R Atkinson², F Ballester³, A Le Tertre⁴, J G Ayres⁵, F Forastiere⁶, B Forsberg⁷, J M Vonk⁸, L Bisanti⁹, R H Anderson², J Schwartz¹⁰ and K Katsouyanni¹¹

¹ Unitat de Recerca Respiratoria i Ambiental, Institut Municipal Investigació Médica (IMIM), 08003-Barcelona, Spain.
² Dept of Public Health Sciences, St George’s Hospital Medical School, London SW17 ORE, UK
³ Escola Valenciana d’Estudis per a la Salut (EVES), 46017-Valencia, Spain
⁴ Environmental Health Unit, National Institute of Public Health Surveillance, France
⁵ Birmingham Heartlands Hospital, Bordesley Green East, Birmingham B9 5SS, UK
⁶ Department of Epidemiology, Health Authority, Rome, Italy
⁷ Dept of Public Health and Clinical Medicine, Umea University, S-901 87, Umea, Sweden
⁸ Faculty of Medical Sciences, Department of Epidemiology and Statistics, University of Groningen, Netherlands
⁹ Department of Epidemiology, Local Health Authority, Milan, Italy
¹⁰ Environmental Epidemiology Program, Dept of Environmental Health, Harvard School of Public Health, Boston, USA
¹¹ Dept Hygiene-Epidemiolgy, 75 Mikras Asias str., 115 27 Athens, Greece

Correspondence to:
Correspondence to:
Dr J Sunyer, Respiratory and Environmental Research Unit, IMIM, c./ Dr Aiguader 80, 08003-Barcelona, Spain;
jsunyer{at}imim.es

Background: Sulphur dioxide (SO₂) was associated with hospital admissions for asthma in children in the original APHEA study, but not with other respiratory admissions.

Aims: To assess the association between daily levels of SO₂ and daily levels of respiratory admissions in a larger and more recent study.

Methods: Time series of daily counts of hospital emergency admissions were constructed for asthma at ages 0–14 years and 15–64 years, COPD and asthma, and all respiratory admissions at ages 65+ years in the cities of Birmingham, London, Milan, Paris, Rome, Stockholm, and in the Netherlands for periods of varying duration between the years 1988 and 1997. A two stage hierarchical modelling approach was used. In the first stage generalised additive Poisson regression models were fitted in each city controlling for weather and season. These results were then combined across cities in a second stage ecological regression that looked at potential effect modifiers.

Results: For an increase of 10 µg/m³ of SO₂ the daily number of admissions for asthma in children increased 1.3% (95% CI 0.4% to 2.2%). Effect modification among cities by levels of other air pollutants or temperature was not found. The SO₂ effect disappeared after controlling for PM₁₀ or CO, but correlation among these pollutants was very high. Other respiratory admissions were not associated with SO₂.

Conclusion: SO₂ is associated with asthma admissions in children, indicating that reduction in current air pollution levels could lead to a decrease in the number of asthma admissions in children in Europe.

Keywords: COPD; air pollution; asthma; respiratory effects; sulphur dioxide; chronic obstructive pulmonary disease

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