## 5 Conclusions  
This report described behavior effects in female rats after exposure to environmentally relevant concentrations of Cr(VI) in drinking water--concentrations that are considered safe for chronic, widespread human consumption. Further, we described how behavior effects of Cr(VI) manifest distinctly across age groups (young, middle-aged, geriatric) and compared these data to our previous report in males to highlight sex differences. Results from this study emphasize the importance of considering age and sex differences in Cr(VI) neurotoxicity, as well as in broader toxicology contexts. Given that rodents endogenously synthesize vitamin C (a key reducer of Cr[VI]) and the adjustment factors for risk assessment from rodent studies to humans, our results indicate a need to revisit and/or revise the current regulations for Cr(VI) in drinking water. The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app1416206/s1](https://www.mdpi.com/article/10.3390/app1416206/s1)]([https://www.mdpi.com/article/10.3390/app1416206/s1](https://www.mdpi.com/article/10.3390/app1416206/s1)), Figure S1: Drinking water Cr(VI) did not affect female rat body mass. Regardless of age or Cr(VI) exposure, there was no impact of Cr(VI) on body mass throughout the study period. Week 0 indicates body mass at the start of the study prior to any Cr(VI) exposure. Data represent the mean \(\pm\) SEM; Figure S2. Cr(VI) impacted the sociability ratio after 11 weeks. We quantified the ratio of interactions with a cagemate vs. an empty cage during the 3-chamber assay after 5 or 11 weeks of Cr(VI) exposure. (A,B) Data were compared across Cr(VI) groups (A, \(n\) = 21, 26, and 25, respectively; B, \(n\) = 23, 26, and 25, respectively). (C,D) Data were then compared across age groups (C, young \(n\) = 6, 7, and 6, respectively; mid-aged \(n\) = 7, 8, and 8, respectively; geriatric \(n\) = 8, 11, and 11, respectively; D, young \(n\) = 8, 8, and 8, respectively; mid-aged \(n\) = 7, 8, and 7, respectively; geriatric \(n\) = 7, 8, and 8, respectively). Four outliers were removed from week 5 (control = 7.0, 0.05 mg/L = 5.0; 0.1 mg/L = 16.0, 5.0), and five outliers were removed from week 11 (control = 10.0; 0.05 mg/L = 11.0, 11.0; 0.1 mg/L = 9.0, 11.0). Data represent mean \(\pm\) SEM. Blue circles are control groups, orange squares are 0.05 mg Cr(VI)/L, and red triangles are 0.1 mg Cr(VI)/L. Figure S3. Cr(VI) impacted the social novelty ratio after 11 weeks. We quantified the ratio of interactions with a cagemate vs. a stranger rat during the 3-chamber assay after 5 or 11 weeks of Cr(VI) exposure. (A,B) Data were compared across Cr(VI) groups (A, \(n\) = 21, 25, and 22, respectively; B, \(n\) = 25, 27, and 27, respectively) (C,D) Data were then compared across age groups (C, young \(n\) = 5, 7, and 6, respectively; mid-aged \(n\) = 8, 8, and 8, respectively; geriatric \(n\) = 8, 10, and 8, respectively; D, young \(n\) = 8, 8, and 8, respectively; mid-aged \(n\) = 8, 7, and 8, respectively; grid-aged \(n\) = 8, 7, and 8, respectively; geriatric \(n\) = 8, 10, and 10, respectively). Six outliers were removed from week 5 (control = 2.0, 6.0; 0.05 mg/L = 9.0, 1.5; 0.1 mg/L = 0.6, 5.0); and four outliers were removed from week 11 (control = 1.33; 0.05 mg/L = 1.83, 2.0; 0.1 mg/L = 1.75). Data represent mean \(\pm\) SEM. Blue circles are control groups, orange squares are 0.05 mg Cr(VI)/L, and red triangles are 0.1 mg Cr(VI)/L. Table S1. Summary of Results from Cr(VI) Groups, Regardless of Age (mean \(\pm\) SEM). Table S2. Summary of Results from Cr(VI) Groups, Sex Differences (mean \(\pm\) SEM). Table S3. Summary of Results from Cr(VI) Groups, Age Differences (mean \(\pm\) SEM). Animal care and maintenance performed by [PERSON], [PERSON], A.W., J.H.T., [PERSON], S.S.W., [PERSON], [PERSON] and [PERSON]. Behavior analyses conducted by [PERSON], [PERSON], [PERSON], [PERSON], M.P. and J.P.W.J. Statistical analyses performed by A.-M.A. and J.P.W.J. Behavior assay equipment provided by J.C. Study design by [PERSON], L.C.