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How does diesel exhaust impact asthma?
  1. John R Balmes
  1. University of California, San Francisco and Berkeley, USA
  1. Correspondence to John R Balmes, University of California, San Francisco and Berkeley, USA; jbalmes{at}medsfgh.ucsf.edu

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Both air pollution health effects researchers and air quality regulatory agencies have been paying increased attention to emissions from motor vehicles in recent years. A growing body of scientific literature supports the concept that exposure to roadways with high traffic density is associated with adverse health effects, including increased risk of negative asthma outcomes. Heavy-duty diesel-powered vehicles like trucks and buses are often driven more frequently on roadways with high traffic density and, as such, diesel exhaust has been suspected to be a major cause of traffic-associated asthma morbidity.

Diesel exhaust is somewhat akin to tobacco smoke in that it is a mixture of particles and gases with many chemical constituents. Diesel exhaust particulate (DEP) is mostly elemental carbon with about 20–40% adsorbed organic compounds, but sulfates, nitrates and metals are also present.1 Polycyclic aromatic hydrocarbons (PAHs) and related compounds such as quinones have been touted as the most toxicologically relevant constituents of DEP, primarily because of their redox potential and ability to cause oxidative stress.2 More than 90% of DEP mass is in particles >1 μm in diameter that can easily be inhaled into the deep lung.1 The vapour phase of diesel exhaust includes carbon monoxide, oxides of nitrogen, sulfur oxides and volatile organic compounds, many of which are known to be respiratory tract irritants such as formaldehyde, acrolein and naphthalene (a volatile PAH).

Many in vitro and animal experimental studies support the toxicity of DEP.1–4 The concept of a tiered response to DEP that is dose-dependent has been advanced which posits that low doses induce oxidative stress and upregulation of antioxidant and phase II enzymes, intermediate doses lead to activation of inflammatory signalling cascades and higher doses to cytotoxicity and apoptosis.2 Organic extracts of DEP …

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  • Linked articles 140053.

  • Competing interests None.

  • Provenance and peer review Commissioned; not externally peer reviewed.

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