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Exposure to diesel exhaust (DE) is common. Previous studies found an inflammatory response, but no effect on lung function after 1 h exposure to 300 µg/m3. We exposed healthy subjects to this concentration for 3h.
Methods
Eighteen healthy volunteers were exposed twice to 300 µg/m3 (400 000 particles /cm3) of diluted DE and twice to clean air (CA; <3µg/m3, 100 particles/cm3) in a stainless steel chamber, in a double-blind cross-over design. Immediately before and after exposure we performed a medical examination, spirometry, rhinometry, and blood sampling (repeated next morning). Symptom scores and Peak Expiratory Flow (PEF) were assessed before, 15 min, 75 min and 135 min into exposure. Generalized Estimating Equation (GEE) models were used to analyze the associations between DE exposure and effects, using relative changes from baseline, with adjustment for exposure sequence.
Results
Self-rated irritation of the eyes and throat was higher during DE than CA exposure, with a statistically significant difference after 75 (eyes), and 135 min (eyes, throat). Signs of irritation in the upper airways were significantly more common after DE exposure (OR=3.2), and tended to be so also for the eyes (OR=3.1, p=0.06). PEF increased during CA, but decreased during DE exposure, with a statistically significant difference after 75 (+4.08 vs -9.58 l/s), and 135 min (+8.11 l/s vs -3.5 l/s). Leukocyte concentrations (next day), especially monocytes (same day, next day) were higher after exposure to DE than CA, and a tendency (p=0.07) toward increased interleukin-6 concentrations was observed (next day). Somewhat unexpectedly we observed a decrease in C-reactive protein (same day), and in Clara cell protein (next day).
Discussion
We found adverse acute effects with regard to symptoms, signs, PEF, and inflammatory markers in healthy volunteers exposed to 300 µg/m3 of DE. These effects were first seen after 75 min of exposure.