Review article Adverse respiratory effects and allergic susceptibility in relation to particulate air pollution: flirting with disaster R.R. Cacciola 1 , M. Sarva ` 2 , R. Polosa 2 1 Istituto di Ematologia; 2 Istituto Malattie Apparato Respiratorio, Universita ` di Catania, Catania, Italy Key words: allergy; diesel exhaust particles; IgE; respiratory symptoms; road traffic pollution. Prof. R. Polosa Istituto Malattie Apparato Respiratorio Universita ` di Catania Ospedale Ascoli-Tomaselli Via Passo Gravina 187 95125 Catania Italy Accepted for publication 27 September 2001 The prevalence of allergic conditions such as asthma, rhinoconjunctivitis and atopic eczema/dermatitis has steadily increased in recent decades. Elicitation of an IgE-mediated allergic trait appears to be determined by the complex interplay of multiple genetic and environ- mental factors. However, although genetic factors in addition to allergen exposure are important, the observed rise in the prevalence of allergic conditions is likely to be ensuing from modifications occurring in the environment (1–3). The remarkable expansion in motor vehicle traffic and its associated emissions has paralleled the world-wide increase in the prevalence of respiratory tract conditions (4). Over the last 40 years the global vehicular fleet has expanded ten-fold and the number of vehicles are predicted to increase even further over the next 20–30 years (5). Estimates by the United Nations indicate that over 600 million people living in cities and towns world-wide are exposed to unhealthy and danger- ous levels of motor vehicle generated air pollutants (6). Although the health effects of urban air pollution on the respiratory tract has been the focus of much research in recent times, it appears that less attention has been given to the potential role of pollutants emitted from motor vehicle exhausts in the elicitation of allergic con- ditions. Several laboratory based studies have dem- onstrated that particulate air pollutants emitted from motor vehicles can induce mucosal inflammation, enhance IgE responses, and heighten airway hyper- responsivenss which could provide an explanation for the increasing prevalence of respiratory symptoms and allergic diseases (7). The present article reviews our current understanding of the mechanisms by which pollutants such as diesel exhaust particles (DEP) enhance the underlying allergic inflammatory response, and the evidence that supports the causative link between particulate air pollution from motor vehicles and increasing allergic diseases. This article will comply with the recently revised nomenclature of allergic disorders proposed by an EAACI task force (8). Particulate air pollutants and respiratory symptoms: epidemiological evidence A number of epidemiological studies in several countries support the view that exposure to traffic-related pollutants is associated with a broad spectrum of adverse short-term respiratory effects in vulnerable individuals. Studies in Japan (9–11) have shown that people living close to main roads with heavy traffic suffered more respiratory symptoms and allergies than those living further away. Similar studies carried out in the UK (12) and in the Netherlands (13, 14) reported increased respiratory symptoms and reduced lung function in those children living in close proximity of roads with high traffic intensity, which positively correlated with the levels of particulate matter in the Allergy 2002: 57: 281–286 Printed in UK. All rights reserved Copyright # 2002 Blackwell Munksgaard ALLERGY ISSN 0105-4538 281