At first blush, you might not think air quality is related to brain health. But what if the two are connected? Air pollution continues to worsen in the developing world, especially in rapidly developing countries like China and India; at the same time, our global population is aging, and dementia rates are expected to rise accordingly. Increasingly, research suggests a link between air pollution exposure and the risk of diseases like Alzheimer’s and Parkinson’s. How might this relationship be possible, and what might it mean for what the world is — or isn’t — prepared to handle in the coming decades?