Response by Li et al to Letters Regarding Article, “Particulate Matter Exposure and Stress Hormone Levels: A Randomized, Double-Blind, Crossover Trial of Air Purification”
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We appreciate the comments by Jordan et al, Yang et al, and Mutlu et al on our recent article1 on particulate matter (PM) exposure and stress hormone levels. We hereby provide additional information and discussion on our findings with regard to the issues raised in these letters.
First, all the participants in our study were second- or third-year undergraduate students from Fudan University and were required to spend ≥50% and 80% of the time inside their dormitories on weekdays and weekends, respectively. According to the self-administered time-location questionnaires, the average time proportion spent indoors was 64.9% on weekdays and 92.4% on weekends during the first stage and 63.0% on weekdays and 91.8% on weekends during the second stage. Paired t tests showed no significant difference between time spent in the dormitories between the first and second stage for each participant …