If you were to ask which is the most polluted city in the world, I couldn't tell you. We don't know.

Mexico City's pollution probably doesn't have a global impact, but all urban areas together do, and the world is urbanizing. If we can understand the pollution impacts of Mexico City, we can apply this new knowledge to other urban areas across the globe.

In the past there have been air campaigns during which researchers have made lots of aerosol measurements, and other ones during which they've emphasized gas measurements. The uniqueness of MIRAGE is that it brings them together, allowing us to study interactions between gases and aerosols.

The pollution is ventilated out by wind almost every day, but then it gets re-polluted each day.

We're not looking so much at pollution inside the city, because that's already fairly well known. We're looking at the outflow. For the first time we'll have an idea of how much pollution is affecting areas outside the city, and be able to understand its full importance.

We're not looking so much at pollution inside the city because that's already fairly well known. We're looking at the outflow. For the first time we'll have an idea of how much pollution is outside the city and be able to understand its full life cycle.