In cities across the globe, road transport remains an important source of air pollutants that are linked with acute and chronic health effects. In the last 20 years, my research group have investigated these associations in human challenge chamber studies in Umea, Sweden; real-world exposure scenarios in London and recently in the megacity Beijing, China. The main particulate matter (PM) components originating from road traffic are engine emissions. The largest single source is derived from diesel exhaust (DE). Indeed, owing to the increased market penetration of diesel engines in many European countries and the fact that they generate up to 100 times as many particles as comparable gasoline engines with three-way catalytic convertors, diesel exhaust particles (DEPs) contribute significantly to the airshed in many of the world’s largest cities.
To investigate effects on the airways, human volunteers (healthy and/or mild asthmatic) were exposed for 1–2 h to whole DE (particulates and the associated gas phase) from an idling engine at concentrations ranging from environmentally relevant (PM10 100 ug/m2, 0.7 ppm NO2) to those commonly experienced in busy diesel-dominated traffic environments (PM10 300 g/m2, 1.6 ppm NO2). By performing blood, bronchoalveloar lavage (BAL), and bronchial mucosal biopsy sampling after exposure, these studies have been instrumental in uncovering a systemic and pulmonary inflammatory response attributed, in part, to the oxidative properties of exhaust PM.
Away from orthodox, controlled exposure chamber studies, work was next undertaken in London. Using the city as the laboratory, real-world exposure scenarios were used to investigate the respiratory effects of short-term exposure to diesel traffic. In adults with mild to moderate asthma, walking for 2 h along a busy city street where traffic is entirely diesel powered (as opposed to in a nearby park) resulted in a significant but asymptomatic reduction in lung function. In line with our studies of humans in exposure chambers and our current understanding of the chain of molecular events, roadside traffic exposures also induced inflammatory changes, namely an increase in sputum neutrophil counts and IL-8 and myeloperoxidase concentrations.
As described above from my research in Umea and London evidence supports an interactive chain of events linking pollution-induced pulmonary and systemic oxidative stress, inflammatory events, and translocation of particle constituents with an associated risk of vascular dysfunction, atherosclerosis, and ischemic cardiovascular and obstructive pulmonary diseases. It is now clearly recognised that exposure to combustion-related PM, at concentrations experienced by populations throughout the world, contributes to pulmonary and cardiac disease through multiple mechanistic pathways that are complex and interdependent.
In contrast to the UK’s long industrial heritage, China has undergone rapid industrialization over the past few decades, adding thousands of kilometres of urban road and hundreds of millions of vehicles. PM emissions from traffic have contributed to increasingly poor air quality in Beijing, threatening public health. In 2016 we started work on a new project in Beijing – Effects of air pollution on cardiopulmonary disease in urban and peri-urban residents in Beijing (AIRLESS). We are examining the impact of air pollution on the health of residents who live in the centre of Beijing with residents who live outside the Beijing urban sprawl in a rural area. The 120 individuals in the rural area are exposed to pollution, but it tends to be more of a coal/biomass type of pollution experienced as part of their everyday lives, whereas in central Beijing it’s more traffic-based pollution. We provide the volunteers with personal air quality monitors and measuring their exposure for 24 hours a day for seven days. This data provides us with a unique view of their personal exposure to air pollution. With this approach, we will learn if the pollution in China results in the same type of biological responses we have seem previously in Umea and London.
About the speaker
Frank Kelly holds the chair in Environmental Health at King’s College London, where he is Director of the Environmental Research Group, Director of the NIHR Health Protection Research Unit on Environmental Hazards and Deputy Director of the MRC-PHE Centre for Environment & Health. Prof Kelly leads a substantial research activity which spans all aspects of air pollution research from toxicology to science policy. He has led studies of the urban airshed within London including the impact of the introduction of London’s Congestion Charging Zone and Low Emission Zone. Other work examines the toxicity of PM associated metals and quinones, diesel and biodiesel exhaust emissions, wood smoke and the identification of biomarkers of traffic exposure.
Prof. Kelly has published over 300 peer-reviewed papers as well as many conference papers and books (as author or editor) on the toxicology and health effects of ozone, nitrogen dioxide and particulate pollution. In addition to his academic work, Prof. Kelly is past President of the European Society for Free Radical Research and past Chairman of the British Association for Lung Research. He provides policy support to the WHO on air pollution issues and he is Chairman of COMEAP the UK’s Department of Health’s Expert Committee on the Medical Effects of Air Pollutants.