In the Home Depot parking lot, some of the men warned me of the air pollution. I told them, on no authority, that air quality has been improving over the past few years. They seemed to know I had nothing to back it up other than my eyes, but now I do.
Lost on Sunday, I came across a vertical garden, grass and shrubs growing a different sort of upwards, a meadow thriving on a wall. I searched the Internet and learned there are two more already. They are part of the greening of Mexico City and they mean less brown air hovering over (and settling in) us. I now have data and examples.