假设你是作者需要回复论文评审专家的意见请将下文的回复翻译问英文：但这个结果的解释比较复杂可能的原因有农村的PM25浓度比城市的暴露浓度低PM25在浓度低的情况下HR的改变值更加明显；也可能与农村和城市人群的不同人口特征、生活习惯等原因 。然而我们也觉得这个解释不够充足需要有更多的探索来支持该发现。在本次手稿中我们修改如下：

Dear Reviewer,

Thank you for your valuable comments on our manuscript. We agree that the interpretation of our results is complex, and there could be several reasons for the observed changes in HR. One possible explanation is that the PM2.5 concentration in rural areas is lower than in urban areas, making the changes in HR more significant in low-concentration environments. Another explanation could be related to the differences in demographic and lifestyle characteristics between rural and urban populations.

However, we acknowledge that these explanations are not sufficient, and further exploration is necessary to support our findings. Therefore, we have made the following modifications to our manuscript to address this issue.

Thank you again for your constructive feedback.

Sincerely, [Your name]