Children and young adults living in polluted megacities are at significantly increased risk of developing Alzheimer's, a study has found.
Researchers at the University of Montana in the US studied 203 autopsies of Mexico City residents ranging in age from 11 months to 40 years.
For the study, published in the Journal of Environmental Research, they tracked two abnormal proteins that indicate the development of Alzheimer's and detected the early stages of the disease in babies less than a year old.
"Alzheimer's disease hallmarks start in childhood in polluted environments, and we must implement effective preventative measures early," said Calderon-Garciduenas from the University of Montana.
The researchers found heightened levels of the two abnormal proteins - hyperphosphorylated tau and beta amyloid - in the brains of young urbanites with lifetime exposures to fine-particulate-matter pollution (PM2.5).
They also tracked Apolipoprotein E (APOE 4), a well-known genetic risk factor for Alzheimer's, as well as lifetime cumulative exposure to unhealthy levels of PM2.5 - particles which are at least 30 times smaller than the diameter of a human hair and frequently cause the haze over urban areas.
The findings indicated that Alzheimer's starts in early childhood.
The researchers found hallmarks of the disease among 99.5 percent of the subjects they examined in Mexico City.