Funding for this research was provided by:
Research program on occupational poisoning and occupational lung disease.
Received: 26 July 2017
Accepted: 26 March 2018
First Online: 11 April 2018
Ethics approval and consent to participate
: The study protocol (reference number: 159) was approved by the Ethical Clearance Committee of the National Institute of Occupational Health and Poison Control of the Chinese Center for Disease Control and Prevention on December 27, 2013. The aim and content of this study and the possible effects of tests were explained to each of the study participants and written consent was obtained. Blood samples were collected under aseptic conditions by experienced nurses.
: For all details of manuscript relating to an individual person, written informed consent for the publication of these details were obtained from the study participants. All authors read and approved the final manuscript.
: The authors declare that they have no competing interests.
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