Funding for this research was provided by:
National Institute for Occupational Safety and Health (R01 OH010791, R01 OH009874)
Received: 27 May 2020
Accepted: 5 September 2020
First Online: 14 September 2020
Ethics approval and consent to participate
: This is a substudy of a parent study which obtained approval from the institutional review board at the University of North Carolina (IRB no. 10-1027). In the parent study all participants provided written informed consent for participation and were asked for permission to store and use their specimen(s) for future studies. Only those who provided consent for stored specimen(s) were included in this analysis.
: Not applicable.
: SPC is on the Genentech speakers bureau; the content of the manuscript has not been influenced by this potential conflict of interest. CLM, FCL, MV, CSA and SRM declare that they have no competing interests.