by April McCarthy
September 09, 2016
Can traffic fumes go to your head?
Ultra-fine particles of metal in exhaust
gases fly up our noses and travel into our brains, where they
contribute to diseases associated with the central nervous system,
and the more congested the city, the bigger the problem.
Iron nanoparticles were already known to be present in the brain -
but they were thought to come from the iron naturally found in our
bodies, derived from food.
Now a closer look at their structure suggests the particles mostly
come from air pollution sources, like traffic fumes and coal
burning. The findings are a smoking gun, says Barbara Maher
of Lancaster University in the UK.
Environmental pollution including carbon particles emitted by car
exhaust, smoking and long term inhalation of dust of various origins
have been recognized as risk factors causing chronic inflammation of
The link between smoking and autoimmune
diseases such as rheumatoid arthritis has also been established.
Diseases associated with inhaled
Increasing evidence indicates that
damage specific parts of the brain is present in a wide range of
neurodegenerative diseases including
demyelinating and psychiatric
Iron is present harmlessly in our bodies in different forms, as it
is part of many biological molecules.
But the form known as
magnetite, or iron oxide,
which is highly reactive and magnetic, has been implicated in
Magnets on the
Maher's team looked at the brains of 37 people who had lived either
in Manchester in the UK or Mexico City.
All contained millions of magnetite
particles per gram of brain tissue, detected by measuring how
magnetic the brain tissue was.
"We can confirm that larger cities
expose their populations to a greater density of magnetite
particles due to the nature of environmental pollution in those
areas," said Timothy Sweet, Professor of Environmental Science
commenting on the study.
The surprise came when the team used
electron microscopes to take a close look at particles in the front
part of the brains of six people.
Round particles of magnetite outnumbered
angular magnetite crystals by about one hundred to one.
Crystal forms are more likely to have a natural source - such as
iron that has come out of the body's cells. But round particles
normally come from melting iron at high temperatures, which happens
when fuel is burned.
Maher says the shape of these particles is compelling evidence that
they come from pollution.
"There is iron as impurities in
fuel, and there is iron in a car engine block," she says. "If
you walk down the street you'll be breathing them in - how could
they not get into your system?"
These magnetite nanoparticles are less
nanometers in diameter, so may be
moving from the air into the nerve endings in our noses, and from
there to the brain, says Maher's team.
The team also found that the brains contained nanoparticles of
metals that are present in car engines but are rare in the body,
such as platinum.
Jo Anne Shatkin, at US environmental health firm Vireo
Advisors, says the findings are a cause for concern.
"It's not that surprising because we
have known for a long time we get exposed to these nanoparticles.
We are just getting a better ability to look at them."
Previous work on cells grown in the lab
has suggested that iron oxide is present in the protein plaques
thought to play a role in Alzheimer's disease, and that it generates
reactive compounds called free radicals, which can kill nerve cells.
Population studies have found that people who live nearer busy roads
have a higher risk of mental impairment in old age.
But these kinds of studies have also
found that our risk of getting Alzheimer's by a particular age is
falling over time, so if air pollution is contributing to the
disease, it doesn't seem to be making it more common.
Even so, steps to reduce air pollution might cut our risk of
Alzheimer's further, says Shatkin.