Reviewer Comments January 31, 2006 Thomas L. Goldsworthy

RE: Gasoline DIPE Vapor Condensate: Embryo-Fe tal Toxicity Study inRats by Inhalation Exposures

A well written report that is complete and comprehensive. Study conduct was appropriate; protocol devi ations did not impact data interpre tations or study outcomes. Test substance analysis and chamber monitoring demons trated the appropriateness of the atmospheric generation techniques and stability of test substance. Exposure concentrations were reasonably close to target, and study exposures allowed for suitable testing of test substance for embryofetal toxicity assessments.

Some reductions were seen in maternal body weight changes and food consumption during the exposure period. Body we ight changes were statistically significant at all doses and generally exposure-dose related (most severe reductions in high does group). Similarly, red nasal discharge was observed in exposed animals at all dose levels. Given the relatively minor changes observed in the low dose exposure group for these endpoint s, I concur that a NOAEL of 2,000 mg/m 3 for maternal effects is appropriate. [editorial: remove ‘marginal’ when presenting body weight gains defici t in summary, conclusion and section 3.3.3] The report states no effect of exposures at any level on pregnancy, in cluding pre- or postimplantation loss, fetal weights or the incidenc e of fetal abnormalities and thus establishes a NOAEL for embryo fetal effects at 20,000 mg/m 3 . Fetal body weights in females and for the litter were decreased in the high exposure group. Text (page 29; 3.4.1) noted that this statistical significant finding was interpreted to not represen t an effect of exposure since other signs of effects on pregnancy outcome were not observed. However, it seems possible to have decreased weight loss without always having accompanyi ng adverse pregnancy outcomes. I suggest to examine related studies to determine if rejection or acceptance of this finding is based on a

consistent basis. The incidence of 14 th (supernumerary, rudimentary) ribs was noted as being increased, non-statistical ly significantly, in th e high exposure group. Data show the finding increased in both fetal and litter analysis, and an increased bilateral effect was also observed.

Text notes that this increased level is “closer to the upper range seen previously in a single group”. It would be useful to present the hi storical data of non-exposed animals for the laboratory as well as to commen t within the context of all AP I-sponsored gasoline studies. I would also suggest a trend-test of raw data in the current study. These suggestions for a more robust analysis would aid in understanding if the NOAEL for embryo should be established at 10,000 mg/m 3 , or as stated in the text, 20,000 mg/m 3 (and would result in modifying text, including summary and conclusions). Text acknowledges that this study was esse ntially a re-run of a previous study. If analysis were completed on the earlier study, text should state if differe nces between the two studies were noted in any of the assessed endpoints. Concordance may provide the ‘robustness’ for placing various findings in the proper context. It would also be useful to know if study design and/or test parameters were change d from the original study and if so, why?

Results were not stated in the Results Section for the data shown in Table 8 on gravid uterine weight. [editorial: Page 10, Introduction. Last sentence, “Because the potential...” is not complete.]