Li, Wei
Wu, Mengyun
Yuan, Fang
Zhang, Huadong
Article History
Received: 24 August 2018
Accepted: 29 November 2018
First Online: 22 December 2018
Ethics approval and consent to participate
: The study protocol was approved by the Ethics Committee of Department of Occupational Health Surveillance, Chongqing, China (reference number 2017014). All participants submitted written informed consent.
: Not applicable
: The authors declare that they have no competing interests.
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