Funding for this research was provided by:
National Natural Science Foundation of China (91643203)
Received: 18 September 2020
Accepted: 12 March 2021
First Online: 25 March 2021
: Written informed consent was acquired from all participants prior to the interview and any procedures. The protocol was approved by the Medical Ethical Review Committee of the National Institute for Occupational Health and Poison Control, Chinese Center for Disease Control and Prevention (protocol number: NIOHP201604).
: Not applicable.
: The authors declare that they have no competing interests.