Received: 26 January 2021
Accepted: 30 September 2021
First Online: 14 October 2021
: This study was approved by the Ethical Committee of Shandong University School of Public Health. Our survey was voluntary, and residents could refuse to participate. All participants (the guardian of illiterate participants) provided informed consent before the face-to-face interview. The data used in this study were anonymized before use. All procedures performed in this study involving human participants were in accordance with the Declaration of Helsinki (as revised in 2013).
: Not applicable.
: The authors declare that they have no competing interests.