Scientists in 2004 studied the brain tissue of children and young adults in Mexico who had died of accidents and were stunned by what they found -- a discovery that rocked the world of neuroscience and has gone largely untested until now.
Almost all of the young people had evidence of Alzheimer's protein plaques scattered throughout their brain tissue.
The only factor linking one case to another was air pollution in Mexico City, which led scientists at the time to hypothesize that smog might be a trigger of Alzheimer's disease -- and that the mind-robbing damage might start early in life.
Now a new group of scientists has picked up where the first team left off. So far, it appears a link may exist between inhaling pollutants and developing damage in the brain.
A nationwide study last year followed the fate of nearly 20,000 women over a 10-year period and found that inhaling pollutants, such as those found in any metropolitan area, exacerbated problems with attention span and escalated memory loss.
Another investigation reported last year, which focused on Boston, revealed that on days when concentrations of traffic-related pollutants were up, the number of strokes increased.
Dr. Heather Volk of the University of Southern California reported last fall that exposure to traffic-related pollution during pregnancy and a child's first year of life appear to be associated with an elevated risk of autism.
The key pollutants, she found, were vehicle-related particulate matter and nitrogen dioxide, a leading precursor of ozone, also known as smog.
In Manhattan, Dr. Sam Gandy, director of the Center for Cognitive Health at The Mount Sinai Hospital, has begun a series of studies testing whether air pollution can trigger the pathological changes linked to Alzheimer's.
His research, which was inspired by the findings in Mexico, focuses on laboratory animals.