Short‐Term Adverse Effects of Carbon Monoxide Pollution on the Respiratory System in Adults: a Systematic Review

Canova C, Torresan S, Maestrelli P. Short-term adverse effects of carbon monoxide pollution on respiratory system in adults: a systematic review. Annals of Respiratory Medicine, February 2010; 1(1):89-98

Review Article

Cristina Canova, Stefania Torresan and Piero Maestrelli
Affiliation: Department of Environmental Medicine and Public Health, University of Padova, Padova, Italy

ABSTRACT

Carbon monoxide (CO) is a gas emitted as a byproduct of incomplete combustion and represents one of the most common and widely distributed air pollutants. Chronic exposure of adults to CO has been associated with neurological injuries and cardiovascular disorders induced by tissue hypoxia. It remains to be established whether environmental CO exposure is associated with short‐term adverse effects on the respiratory system. This paper aims to review the investigations that considered the effects of outdoor CO on lung function and hospital or emergency admissions for respiratory causes in adults. The studies were identified by searching electronic databases from 1990 to September 2009. The first search identified 82 papers that considered the effect of outdoor pollution on lung function in adults. From these, just six panel studies measured CO among the air pollutants. We identified three studies that reported a significant association between lung function and airborne CO in adult asthmatics and one in chronic obstructive pulmonary disease (COPD) patients. Overall, there is moderate evidence that CO affects lung function in asthmatics, whereas inconsistent results are available in COPD patients. The search on CO effects on respiratory exacerbation identified 23 time series papers, which considered the association between daily outdoor CO measures and hospital admissions or emergency visits for respiratory diseases. A significant association between CO pollution and respiratory diseases was detected by the majority of these studies, in particularly considering COPD. A direct association between CO and exacerbation of respiratory diseases lacks biologic plausibility. CO could be a marker of other combustion products, measured or not measured in ambient air, such as ultrafine particles. If CO is a marker of other harmful substances, possibly the limits based on its biological properties are not adequate to protect human subjects from adverse reactions.

Keywords: air pollution, spirometry, respiratory diseases, lung function, hospitalization, carbon monoxide, exacerbation
Correspondence: Cristina Canova, Department of Environmental Medicine and Public Health, University of Padova, Via Loredan 18, 35151 Padova, Italy. Tel: (39)‐0498275752; Fax: (39)‐0498275392; e‐mail: cristina.canova@unipd.it