Statistical Analyses

PM concentrations were evaluated midway through each exposure period and reported as arithmetic means across the exposure campaign days with less than 10% variation. PM concentrations for each exposure batch were averaged and plotted as a distribution of all exposures. Particle number (PN) concentrations were measured at the beginning of each exposure period. The particle number mean values were calculated as geometric means of the five exposures. Histochemistry, western blot, MRI, and NOR were analyzed using a general linear model with main effects for nPM, BCAS, and the nPM + BCAS interaction (testing for synergy). Pairwise comparisons used Tukey Kramer adjustment for multiple comparisons. Two-tailed unpaired Student’s t-tests were used to evaluate the effect of behavioral testing/food deprivation on histological analysis. For the 8-arm radial maze, a repeated measures analysis with mixed effect models (over 8 averaged blocked trials) was used to analyze effects of groups and blocked trial number. These models were run in two ways: a) a one-factor model compared the four groups (FA, nPM, FA + BCAS, nPM + BCAS) over the eight trials; and b) a two-factor model analyzed the main effects for nPM, BCAS, and the nPM + BCAS interaction over the eight trials. Mean slope (linear trend in the behavior outcome over trials) was analyzed using a linear mixed effects model with main effects for nPM, BCAS, and the nPM + BCAS interaction (synergy). For the NOR test, a one-way analysis of variance (ANOVA) was used to analyze baseline behavior between cohorts. Statistics were performed using SAS (Version 9.4, SAS Institute Inc.) and GraphPad Prism (Version 9.1.0, GraphPad Software). Data are presented as mean±standard error (SE). Alpha level of 0.05 was chosen for statistical significance. For RNA-Seq, results were prioritized according to false discovery rate adjusted p-value (q-value), with a level of 0.05 for significance.