Southern California freeway pollution, already linked to heart and respiratory problems, causes significant brain damage in mice, according to a study released on Thursday.
The damage is done not by smog but by tiny particles, each roughly one-thousandth the width of a human hair, made up of burning fossil fuel and weathering of car parts and pavement, the University of Southern California study found.
Exposure to the particles, which are too small to be captured by car filtering systems, were shown to significantly damage neurons used in learning and memory, as well as cause signs of inflammation associated with premature aging and Alzheimer's disease.
"We're looking at one particular component of air pollution. These are very, very small particles that aren't really studied or looked at by the (Environmental Protection Agency) even," said Todd Morgan, a USC gerontology professor and author of the study.
Morgan said the study was the first to explore in depth the effects of road pollution on brain cells. He also said it should prompt further review of potential health hazards, for example to children who attend schools near major freeways.
To conduct the study, published in the journal Environmental Health Perspectives, scientists recreated air laden with freeway particulate matter in a laboratory and exposed live mice for a total of 150 hours over 10 weeks.