The Toxicity of Diesel Exhaust: Implications for Primary Care

Irina N. Krivoshto, BA; John R. Richards, MD; Timothy E. Albertson, MD, MPH, PhD; Robert W. Derlet, MD


J Am Board Fam Med. 2008;21(1):55-62. 

In This Article

Diesel Exhaust Composition

There are many components of diesel exhaust, including (1) carbon monoxide and carbon dioxide; (2) nitrogen oxides; (3) sulfur oxides; (4) hydrocarbons; (5) unburned carbon particles (soot); and (6) water.[2] Exhaust from diesel engines is considered to contribute to more than 50% of ambient particulate matter with a mass median aerodynamic diameter less than 10 µm (PM10), greatly contributing to overall air pollution. For fine particulate matter with a diameter below 2.5 µm (PM2.5) and ultra-fine particles with a diameter below 0.1 µm, this contribution is even higher.[1] These carbon particles are small enough to be inhaled and deposited in the lungs but have a large surface area. Organic compounds from diesel exhaust with known toxic and carcinogenic properties, such as polycyclic aromatic hydrocarbons (PAH), adhere easily to the surface of the carbon particles and are carried deep into the lungs.[4] The majority of these particles tend to be found in the greatest concentration within the immediate vicinity of busy streets or highways.[7,8] Diesel engines emit other toxic compounds in disproportionately higher concentrations than gasoline engines, including nitrogen oxides, sulfur oxides, ozone, formaldehyde, benzene, and smaller organic molecules. Diesel engines also produce 26% of the total nitrogen oxides in outdoor air. Nitrogen oxides are a major contributor to ozone production and smog. More attention has been focused on the hundreds of different types of organic molecules created from the high-compression ratios of diesel engines because many are highly toxic.[1] A summary of the composition of diesel exhaust and its biological effects are detailed in Table 2 .


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