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Exposure to diesel exhaust particles raises risk of pneumococcal disease


A new study, published in the Journal of Allergy and Clinical Immunology, shows that exposure to diesel exhaust particles (DEPs) can increase an individual’s susceptibility to pneumococcal disease.

The bacterium Streptococcus pneumoniae is the most common cause of pneumonia and meningitis and the leading cause of infectious disease deaths in under-5s and elderly groups worldwide. In the majority of healthy people, this bacterium lives harmlessly in the back of the nose and throat without causing any symptom. However, if the pneumococcus gains access to normally sterile sites in the body, such as the lungs and blood, it has the potential to cause life-threatening diseases.

To find out more about the conditions that allow this ordinarily harmless bacterium to progress into such severe invasive diseases researchers from the University of Liverpool, Queen Mary’s University, London and Trinity College Dublin, conducted a study examining the role of DEPs in the development of pneumococcal disease.


The World Health Organisation (WHO) estimates that air pollution is responsible for seven million deaths per year, with seven per cent of these attributable to pneumonia. An estimated 37 per cent of the world’s population lives in areas where levels of airborne pollution exceed WHO guideline limits.

DEPs, a major component of air pollution worldwide, are the particulate component of diesel exhaust, which includes diesel soot and aerosols such as ash particulates, metallic abrasion particles, sulphates, and silicates.

The researchers, led by Professor Aras Kadioglu from the University of Liverpool’s Institute of Infection & Global Health, used a combination of mouse models and lab-based assays in both mouse and human cells to provide insight into the link between DEP exposure and pneumococcal disease.

The researchers found that following exposure to DEPs, airway macrophages, which are key immune cells for controlling bacterial infections and removing debris from the body, become congested with DEPs, reducing their ability to kill the pneumococcus. This allows the bacteria to survive more easily in the airways, invade the lungs, and cause significant inflammation, which eventually leads to bacterial translocation into blood, thereby causing severe disease.


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