Fig. 1
Diesel exhaust (DE) concentration–response for symptom categories. Symptoms were recorded before, and at 4 and 24 h after the start of exposures to filtered air and diesel exhaust (DE) standardized to 20, 50 and 150 µg/m3 PM2.5. X axes show change in symptom scores from baseline, while Y axes show PM2.5 concentrations (µg/m3). Shaded grey regions represent 95% confidence intervals, and the horizontal dashed lines represent 0 (no change from baseline). Linear mixed effects models were fitted with participant ID as a random effect: *P ≤ 0.05