Fig. 2: Emotion expression discrimination performance before and after exposure sessions.

Changes in expression discrimination performance pre- and post-exposure (a) for the two pollution exposure conditions (averaged across both inhalation conditions); and (b) across all four exposure/inhalation condition combinations. Average expression discrimination performance, measured as \({{{{\rm{d}}}}}^{{\prime} }\), declined significantly after exposure compared to before exposure (a). A repeated measures ANOVA with Bonferroni corrections revealed a statistically significant main effect of time [F(1, 25)  = 8.167, p  = 0.008]. Critically a greater decline in expression discrimination performance was identified following PM pollution exposure (a: red line) compared to clean air exposure (a: blue line). The interaction was statistically significant, as determined by a repeated measures ANOVA with Bonferroni corrections for multiple comparisons [F(1, 25)  = 5.552, p  = 0.027]. Inhalation pathway did not mediate changes in expression discrimination performance (b), as no significant three-way interaction was found using a repeated measures ANOVA with Bonferroni corrections [F(1, 25)  = 0.868, p  = 0.360]. n  = 26 independent human participants (biological replicates), within a fully repeated measures design. a Data are presented as mean values +/- SEM; (b) Median represented by the horizontal line, box indicates interquartile range (25th-75th percentiles), whiskers show full data range between minimum and maximum; white circles indicate individual data points; black diamonds indicate condition means; *p  < 0.05; **p  < 0.01. Source data are provided as a Source Data file.