EPA has had varied opinions on the scientific merit of the OIG Scientific Analysis of Perchlorate (External Review Draft). In January 2009, after consultation with EPA scientists, George Gray, the former ORD Assistant Administrator and EPA Science Advisor, recommended that the major finding of the OIG Scientific Analysis of Perchlorate should be reviewed by the National Academy of Sciences (NAS). By contrast, in March 2009, EPA's OW and ORD comments provided unfavorable opinions on the approach and findings presented in the OIG Scientific Analysis of Perchlorate. The opinions of the other commenters are both favorable and unfavorable. Although the scientific community has been actively studying perchlorate toxicity over the last 17 years - since EPA's issuance of a provisional RfD in 1992 - a consensus opinion on the toxicity of perchlorate eludes the risk assessor community.