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 …

我们赞赏Jordan等人，Yang等人和Mutlu等人对我们最近关于颗粒物（PM）暴露和应激激素水平的文章^1的评论。我们在此就这些信函中提出的问题提供更多信息并就我们的发现进行讨论。

首先，我们研究的所有参与者均为复旦大学的二年级或三年级本科生，被要求分别在工作日和周末花费≥50％和80％的时间在宿舍内。根据自我管理的时间-位置调查表，第一阶段在工作日的室内平均时间比例为64.9％，周末为92.4％，第二阶段的平日为63.0％，周末为91.8％。配对的t检验显示，每个参与者在第一阶段和第二阶段之间在宿舍所花费的时间之间没有显着差异……