Learning objectives: Identify any changes in cytokine (mediator) concentrations in nasal secretions after healthy individuals were experimentally exposed to urban dust. Recall what connection there was, if any, between post-exposure cytokine levels in nasal secretions on the one hand, and, on the other, counts of inflammatory cells and nasal symptoms. Report the investigators' conclusions as to whether exposure to urban dust is a cause of persistent inflammation and chronic airway disease.
Abstract: Thirty healthy volunteers were nasally exposed to control air and urban dust (SRM 1649a) in concentrations of 150 and 500 microg/m3 for 3 hours. Thirty minutes, 8 hours, and 24 hours after exposure, nasal cytologies were obtained, and nasal secretion levels of interleukin (IL)-1beta, IL-6, IL-8, tumor necrosis factor-alpha, epithelial neutrophil activating protein-78, monocyte chemoattractant protein-1, and substance P were determined. Twenty-four hours after exposure to 500 microg/m3, nasal secretion levels of IL-1beta increased 72.3% (0-150.2%, P=0.002), levels of IL-6 increased 42.2% (-28-161.9%,P=0.01), and levels of IL-8 increased 19.7% (-20.3-60.5%, P=0.03; median and 95% confidence interval). These cytokines correlated closely with nasal inflammatory cell counts. No exposure-related changes of tumor necrosis factor-alpha, monocyte chemoattractant protein-1, epithelial neutrophil activating protein-78, and substance P levels were observed. These results provide experimental support for recent epidemiological observations that short-term increase of outdoor particulate matter concentration increases the frequency of upper respiratory diseases.