Health effects of diesel exhaust emissions

Epidemiological studies have demonstrated an association between different levels of air pollution and various health outcomes including mortality, ex acerbation of asthma, chronic bronchitis, respiratory tract infections, isc haemic heart disease and stroke. Of the motor vehicle generated air polluta nts, diesel exhaust particles account for a highly significant percentage o f the particles emitted in many towns and cities. This review is therefore focused on the health effects of diesel exhaust, and especially the particu lar matter components. Acute effects of diesel exhaust exposure include irritation of the nose and eyes, lung function changes, respiratory changes, headache, fatigue and na usea. Chronic exposures are associated with cough, sputum production and lu ng function decrements. In addition to symptoms, exposure studies in health y humans have documented a number of profound inflammatory changes in the a irways, notably, before changes in pulmonary function can be detected. It i s likely that such effects may be even more detrimental in asthmatics and o ther subjects with compromised pulmonary function. There are also observations supporting the hypothesis that diesel exhaust i s one important factor contributing to the allergy pandemic. For example, i n many experimental systems, diesel exhaust particles can be shown to act a s adjuvants to allergen and hence increase the sensitization response. Much of the research on adverse effects of diesel exhaust, both in vivo and in vitro, has however been conducted in animals. Questions remain concerni ng the relevance of exposure levels and whether findings in such models can be extrapolated into humans. It is therefore imperative to further assess acute and chronic effects of diesel exhaust in mechanistic studies with car eful consideration of exposure levels. Whenever possible and ethically just ified, studies should be carried out in humans.