Cardiovascular effects of particulate air pollution exposure: time course and underlying mechanisms

Air pollution is now recognized as an important independent risk factor for cardiovascular morbidity and mortality and may be responsible for up to 3 million premature deaths each year worldwide. The mechanisms underlying the observed effects are poorly understood but are likely to be multifactorial. Here, we review the acute and chronic effects of air pollution exposure on the cardiovascular system and discuss how these effects may explain the observed increases in cardiovascular morbidity and mortality.

Ozone exposure enhances mast-cell inflammation in asthmatic airways despite inhaled corticosteroid therapy

Asthmatics are recognised to be more susceptible than healthy individuals to adverse health effects caused by exposure to the common air pollutant ozone. Ozone has been reported to induce airway neutrophilia in mild asthmatics, but little is known about how it affects the airways of asthmatic subjects on inhaled corticosteroids. We hypothesised that ozone exposure would exacerbate the pre-existent asthmatic airway inflammation despite regular inhaled corticosteroid treatment. Therefore, we exposed subjects with persistent asthma on inhaled corticosteroid therapy to 0.2 ppm ozone or filtered air for 2 h, on 2 separate occasions. Lung function was evaluated before and immediately after exposure, while bronchoscopy was performed 18 h post exposure. Compared to filtered air, ozone exposure increased airway resistance. Ozone significantly enhanced neutrophil numbers and myeloperoxidase levels in airway lavages, and induced a fourfold increase in bronchial mucosal mast cell numbers. The present findings indicate that ozone worsened asthmatic airway inflammation and offer a possible biological explanation for the epidemiological findings of increased need for rescue medication and hospitalisation in asthmatic people following exposure to ambient ozone.

Diesel exhaust exposure enhances the ozone-induced airway inflammation in healthy humans

Exposure to particulate matter and ozone cause adverse airway reactions. Individual pollutant effects are often addressed separately, despite coexisting in ambient air. The present investigation was performed to study the effects of sequential exposures to diesel exhaust (DE) and ozone on airway inflammation in human subjects. Healthy subjects underwent bronchoscopy with bronchoalveolar lavage (BAL) and bronchial wash (BW) sampling on two occasions. Once following a DE exposure (with 300 mug.m(-3) particles with a 50% cut-off aerodynamic diameter of 10 mum) with subsequent exposure to O(3) (0.2 ppm) 5 h later. The other bronchoscopy was performed after a filtered air exposure followed by an ozone exposure, using an identical protocol. Bronchoscopy was performed 24 h after the start of the initial exposure. Significant increases in neutrophil and macrophage numbers were found in BW after DE followed by ozone exposure versus air followed by ozone exposure. DE pre-exposure also raised eosinophil protein X levels in BAL compared with air. The present study indicates additive effects of diesel exhaust on the ozone-induced airway inflammation. Together with similar results from a recent study with sequential diesel exhaust and ozone exposures, the present data stress a need to consider the interaction and cumulative effects of different air pollutants.

Ozone-induced bronchial epithelial cytokine expression differs between healthy and asthmatic subjects

BACKGROUND

Ozone (O3) is a common air pollutant associated with adverse health effects. Asthmatics have been suggested to be a particularly sensitive group.

OBJECTIVE

This study evaluated whether bronchial epithelial cytokine expression would differ between healthy and allergic asthmatics after ozone exposure, representing an explanatory model for differences in susceptibility.

METHODS

Healthy and mild allergic asthmatic subjects (using only inhaled beta2-agonists prn) were exposed for 2 h in blinded and randomized sequence to 0.2 ppm of O3 and filtered air. Bronchoscopy with bronchial mucosal biopsies was performed 6 h after exposure. Biopsies were embedded in GMA and stained with mAbs for epithelial expression of IL-4, IL-5, IL-6, IL-8, IL-10, TNF-alpha, GRO-alpha, granulocyte-macrophage colony-stimulating factor (GM-CSF), fractalkine and ENA-78.

RESULTS

When comparing the two groups at baseline, the asthmatic subjects showed a significantly higher expression of IL-4 and IL-5. After O3 exposure the epithelial expression of IL-5, GM-CSF, ENA-78 and IL-8 increased significantly in asthmatics, as compared to healthy subjects.

CONCLUSION

The present study confirms a difference in epithelial cytokine expression between mild atopic asthmatics and healthy controls, as well as a differential epithelial cytokine response to O3. This O3-induced upregulation of T helper type 2 (Th2)-related cytokines and neutrophil chemoattractants shown in the asthmatic group may contribute to a subsequent worsening of the airway inflammation, and help to explain their differential sensitivity to O3 pollution episodes.