Section 211(b) Research Group Response to Independent Peer Reviewer Comments On:

Gasoline DIPE Vapor Condensate: Embryo-Fetal Toxicity Study in Rats by Inhalation Exposure HLS Study No. 05-4287

In the 211(b) testing program, the draft final repor ts of all developmental toxicity studies on vapor condensates of gasoline + oxygenates were reviewed by two independent peer reviewers: Dr. Thomas Goldsworthy, Consultant, and Dr. Richard Schlesi nger, Pace University (formerly of New York University School of Medicine).

The reviewers concur that the study was properly conducted and scientifically sound. None of the

reviewers’ comments or recommendations invalidates th e study. Both of the reviewers questioned the selection/justification of the developmental NOAEL.

The 211(b) Working Group (WG) responses are organized by reviewer.

Dr. Goldsworthy

Dr. Goldsworthy recommended that the analysis of da ta for developmental effects be made more robust by examining related studies for value in interpretation of fetal body weight differences and incidence of

14 th ribs, as well as examination of the original st udy [with partial data compromise on internal observations] for concordance. The WG will provide the original study (EMBSI Study No. 171734, 2008) to the HLS study director for review and consideration. In the pr evious study at EMBSI, administration of the test substance was not associated with statistically signi ficant changes in mean fetal body weight or any statistically significant skeletal anomalies (Appendix K, Statistician’s Report). The WG will request that appropriate historical control information on relevant developmental endpoints be included as an appendix to the report. The WG will request that the study director review the overall 211b developmental toxicity program findings for possible consideration in the interp retation of the results of this study. The study director was a co-author on a presentation of the results of this study and others in the 211b developmental toxicity testing program in rats (Robert s, et. al, 2009). In this poster presentation, the study was interpreted to have a maternal NOEL of 2000 mg/m 3 /day based upon reductions in gestation body weight change and food consumption at the hi gher exposure levels, and a developmental NOEL of 10,000 mg/m 3 /day based upon lowered fetal body weight at 20,000 mg/m 3 /day. The higher, but not statistically significant, incidence of rudimentary lumb ar ribs was noted in the poster but not defined as attributed to exposure.

Dr. Goldsworthy observed that the results for gravid uterine weight (Table 8) were not stated in the Results section of the report. The WG will request that gravid uterine weight be included in the text of the Results section.

Dr. Goldsworthy recommended the following two editorial changes:(a) Remove the word, “marginal,” when presenting body weight gain deficits in the Summary, Conclusions (Section 3.3.3)

a. The WG will request this deletion in th e Summary, Results (section 3.3.3), and Conclusion (section 4) (b) Correct the incomplete (last) sentence in the Introduction that begins, “Because the potential...”

a. The WG will request that the first word , “Because,” be removed from the final

sentence in the Introduction.

Dr. Schlesinger

Dr. Schlesinger commented that there should be no par ticles in the chamber air if it is properly filtered, whereas particulates were measured in the chambers (0.0036 – 0.0063 mg/m 3 ). Appropriate filters were in place, but some particles are invariably present in chamber atmospheres, representing background air. The primary purpose of particulate measurements in a study utilizing high vapor concentrations is to make certain that vapor condensation is not occurring, and to preclude the possibility of aerosol formation. We believe that the particles in the chambers reflect ambient background levels.

Dr. Schlesinger agreed with the conclusions in the draf t report, but commented that the differences in fetal weight noted for the high exposure group, which were not considered to be an effect of exposure since the difference from control was very small, should not be summarily discounted. This comment is similar to a suggestion from Dr. Goldsworthy. The lab will be asked to review their interpretation in light of typical variability within their historical control data as well as to consider whether the slight but statistically si gnificant differences noted for fetal body weight, 3- 4% of control values, are truly considered not to represent an effect of the exposures, as the report is currently written, or not to represent a biologica lly or toxicologically relevant difference. Fetal body weight was a consideration in the sel ection of the developmental NOEL, 10,000 mg/m 3

.

Dr. Schlesinger commented that error bars should appear on Figures 1 and 2. Figures 1 and 2 represent gestation body weights and food consumption. The WG will ask the study director to include error bars if this is possible within the program that generates the figures. If the program is unable to do this, we will not pursue this request further, since Tables 4 and 5 provide standard deviati ons and statistical significance.