Authors' reply


Key Points

  • Dr. Crane raises a number of interesting points, but these serve to support not distract from, the conclusions of our paper.
  • Without independent verification that the source inputs used are appropriate and sufficient, the results of EPA's Chemical Mass Balance Model (CMB) cannot be used to verify the contribution of a given source.
  • Neither Van Metre and Mahler's (2010) nor Crane's (2014) use of CMB demonstrates whether refined tar sealers are actually a source in any urban sediment.
  • When using the results of receptor models to promote source control policy, care must be taken to clarify the underlying assumptions and uncertainty.