Received: 3 August 2017
Accepted: 9 February 2018
First Online: 9 March 2018
Compliance with ethical standards
: All authors were employees of Thermo Fisher Scientific at the time of the study. None of the research in this study was supported by outside funding agencies. All source samples, other than deposited trace DNA, were purchased from commercial vendors as noted in the Materials and Methods section. All procedures involving trace DNA samples collected in-house were performed in accordance with the ethical standards established at Thermo Fisher Scientific. Informed consent was obtained from all individual participants in the trace DNA portion of the study except for discarded and found cigarette butts. Human samples, purchased from the Interstate Blood Bank (Memphis, TN), Boca Biolistics (Coconut Creek, FL), and Serological Research Institute (Richmond, CA), were originally obtained with informed consent release and in compliance with all US FDA and state guidelines.