Applying methods of textual and stylometric analysis to all 119,225 speeches made in the Canadian House of Commons between 2006 and 2011, we establish that air pollution reduces the speech quality of Canadian Members of Parliament (MPs). Exposure to fine particulate matter concentrations exceeding 15 μg/m3 causes a 3.1 percent reduction in the quality of MPs speech (equivalent to a 3.6 months of education). For more difficult communication tasks the decrement in quality is equivalent to the loss of 6.5 months of schooling. Our design accounts for the potential endogeneity of exposure and controls for many potential confounders including individual fixed effects. Politicians are professional communicators and as such the analysis contributes to our evolving understanding of how pollution exposure impacts the execution of work-relevant skills. Though we are cautious in interpreting the effect as a clean metric for performance, the effect size is around half that established in recent research for workers engaged in physical work tasks. Insofar as the changed speech patterns reflect diminished mental acuity the results make plausible detrimental effects of air pollution on productivity in a wider set of communication-intensive work settings.