Diesel And Automobile Exhaust / Health Effects

[Guest allanopie]

Diesel and Automobile Exhaust / Health Effects

Diesel exhaust contributes to ambient sulfur oxides, ozone precursors, and aerosols, seems to contribute to chronic respiratory morbidity and mortality, and probably contributes to the cancer risk of urban air pollution. Mutagenic and carcinogenic compounds (such as PAHs) are adsorbed to diesel soot.

Diesel clearly causes cancer in rats (but not hamsters), and the mechanism may be chronic inflammation, hyperplasia, multifocal fibrosis, and macrophage particle clearance overload.45 Diesel may be a co-carcinogen, and extrapolation of risk from laboratory animals is perilous. Diesel has been demonstrated to modulate the immune response, acting as an adjuvant in the specific IgE response, and augmenting non-specific IgE production and inflammatory cytokine synthesis, up regulating the atopic state, increasing eosinophil degranulation, and increasing the inflammatory respiratory response to allergen. Non-specific IgE augmentation has been associated with increased odds of asthma.[sunyer, 1996 #809] Some vapor phase constituents cause bronchoconstriction.

In humans, occupational case control and cohort studies have found a small but generally consistent association of prolonged exposure to high diesel concentrations, when adjusted for cigarette smoking, with a relative risk (RR) of lung cancer incidence of 1.4 to 1.7 in the best studies. While most studies have problems with exposure assessment, wide confidence intervals, and low effect magnitude,46 (http://www.epa.gov/ncea/diesel.htm) a recent meta-analysis47 of over twenty studies examining occupational exposure to diesel exhaust, confirmed a statistically significant RR of 1.33 for lung cancer, again with adjustment for cigarette smoking.

Heavy exposure to diesel is clearly associated with pulmonary inflammation, with some evidence of increased incidence of respiratory symptoms (cough, phlegm, and wheezing) and small work shift pulmonary function decrements; heavily exposed cohorts may have elevated risks of mortality from chronic lung disease (chronic obstructive lung disease and respiratory infection).46

Community studies (many of them well controlled for important confounders) have found living, going to school, or working in proximity to high traffic density, to be associated variously with asthma, chronic bronchitis, and allergic rhinitis. Important variables seem to be traffic density, truck traffic density, and distance to the roadway. Many other roadway related factors may contribute, including combustion related particles, road dust, nitrogen oxides from non-diesel engines, tire particle aerosols, and other volatile organic compounds.

Source:

Air Pollution and Primary Care Medicine

http://psr.igc.org/nrtb-airpol-primcare.htm

Edited June 16, 2006 by allanopie