On the growing list of maladies pegged to dirty air, the most unsettling may be brain damage. A particularly vivid bit of evidence that pollution triggers dementia came in 2002 from a team of scientists who examined the brains of puppies from Mexico City, known at the time for its awful air. The markers they found—degenerating neurons, twisted protein fibers, plaque deposits—were the same telltale signs doctors use to diagnose Alzheimer’s in humans. That pointed not just to a link between dirty air and a dreaded ailment, but to the troubling possibility that the path toward dementia might be laid out in youth, not old age. That likelihood grew stronger still when the neuropathologist who led the dog study conducted autopsies on children and young adults killed in accidents and found early markers of Alzheimer’s in 40 percent of those who’d lived with high levels of pollution, but none in those who had breathed clean air. She saw, too, in the brains of young people the red flags of Parkinson’s, along with inflammation, impaired blood flow, and genetic changes, all frightening harbingers of neurological decline. A follow-up study found immediate effects on children’s function, too. Kids who lived in the most polluted places and also carried a gene linked to Alzheimer’s had short-term memory loss and IQs 10 points lower than their peers’.
—Adapted from Choked: Life and Breath in the Age of Air Pollution, by Beth Gardiner, published by the University of Chicago Press