Comment submitted by Edmund Crouch, Cambridge Environmental Inc.

The 1st draft Health REA refers at page 4-13 to a document: Hall et al. (2012), which is given in the reference list at page 4-18 as: "Hall, E., Eyth, A., Phillips, S. (2012) Hierarchical Bayesian Model (HBM)-Derived Estimates Air Quality for 2007: Annual Report. EPA/600/R-12/538. Available on the Internet http://www.epa.gov/heasd/sources/projects/CDC/AnnualReports/2007_HBM.pdf." Attempting to download this document returns only a zero-length document of the given name. Please provide the cited document at the cited link location; this document (with the same link as above) is listed on the EPA website from http://www.epa.gov/heasd/sources/projects/CDC under the heading "Annual Reports (for CDC: 2001 - 2006) – HBM Only" and is indicated to be 300 pp and 32.5 Mbyte in size.