Where Do Inhaled Fossil Fuel-derived Particles Go?
804 - 806
AMERICAN JOURNAL OF RESPIRATORY AND CRITICAL CARE MEDICINE
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There is increasing evidence that inhalation of fossil fuel–derivedparticulate matter (PM) is associated with a wide range ofnonpulmonary health effects. For example, a pan-Europeanstudy reported an association between urban PM exposure duringpregnancy and reduced birth weight at term (1), and a recentpopulation-based Canadian cohort study reported an increasedrisk for incident dementia in people living less than 50 m from amajor traffic road, especially in residents of major cities (2). Aplausible and widely accepted explanation for these effects is thatPM, via induction of oxidative stress, stimulates the release ofinflammatory mediators into the systemic circulation from lowerairway cells (3). An alternative mechanism, namely, that inhaledparticles directly enter the systemic circulation, deposit in distantorgans, and trigger pathology has, until recently, suffered from alack of convincing evidence. Indeed, an influential study of healthyadult volunteers published more than 10 years ago found noevidence for translocation of technetium-99–labeled carbon nanoparticles (4). Although, in the same year, a study performed inmice exposed to intratracheal instillation of ultrafine carbon blackfound particles within systemic monocytes and on the surface ofred blood cells (5), damage to the air–tissue interface fromunphysiologically high concentrations of PM could not beexcluded. However, the evidence for translocation has recentlybeen significantly strengthened