vessels. The emerging surprise is what
it might do to the brain. Increasingly,
studies have been highlighting inflammation-provoking nanopollutants as a
potential source of nerve cell damage.
KOUJI ADACHI AND PETER R. BUSECK/E NVIRONMEN TAL SCI. TECHNOL. 2010
Calderón-Garcidueñas has been correlating Mexico City’s stew of air pollutants with a suite of symptoms in people
of all ages. In March in Salt Lake City at
the annual meeting of the Society of Toxicology, Calderón-Garcidueñas unveiled
some of her latest data. At age 11, Ana
shows persistent, growing brain lesions,
the toxicologist reported. As do the other
Mexico City children surveyed. They also
exhibit cognitive impairments in memory, problem solving and judgment and
deficiencies in their sense of smell compared with age-matched children from a
cleaner city 120 kilometers away.
Other toxicologists at the meeting
Mexico City’s air is choked with smog.
But scientists are finding that another
menace— particles too small to see
—may pose a serious health threat.
presented data, largely from animal
studies, tracking the movement of
billionth-of-a-meter–scale particles into
the brain, where they triggered inflammation and abnormalities characteristic
of Alzheimer’s or Parkinson’s.
Until recently, most air pollution toxicology has focused on impacts to the
lungs and heart, observes James Antonini
of the National Institute for Occupational
Safety and Health’s lab in Morgantown,
W. Va. The challenge now, he says, is to
identify which pollutants are harming the
nervous systems of Ana and others who
live in areas with particularly dirty air.
Mexico City is not the only source of
real-world pollution that has been linked
to mental impairments.
Ulrich Ranft and colleagues at the Environmental Health Research Institute at
Heinrich Heine University in Düsseldorf, Germany, studied 400 or so highly
functioning local women in their mid- to
late 70s. Elderly women who lived within
50 meters of very busy streets exhibited
poorer memory skills than did women
of the same age whose homes were well
removed from highly trafficked roadways,
the team reported in the November 2009
Mn, Fe, Zn, Pb
The study turned up no similar link
between cognitive scores and average
levels of particles in the women’s com-
munities. That makes sense, Ranft says,
because the levels of ultrafine motes
emitted by traffic can be quite high along
streets, “but drop off very fast, falling to
almost background levels when you get
just 100 meters away from the road.”
Young children’s minds may be espe-
cially sensitive to tiny airborne particles
spewed by traffic, according to Shakira
Franco Suglia of the Harvard School of
Public Health in Boston and her col-
leagues. In studies of roughly 200 Bos-
ton 10-year-olds, the researchers found
that those living in areas with the highest
average airborne concentrations of soot,
a pollutant primarily associated with
traffic, had lower IQs and lower scores
on memory tests.
The team divided the kids by exposure
levels into four groups. The average IQ
drop between one group and the next
averaged about three points — comparable to that seen in kids whose mothers
had smoked during pregnancy, Franco
Suglia’s group reported in 2008 in the
American Journal of Epidemiology.
Taking note of non-scents
A few studies, including the recent one
by Ranft’s group, have also observed
a somewhat impaired sense of smell
among people living in polluted regions.
At the toxicology meeting, Calderón-Garcidueñas reported that kids and young
Mn, Fe, Zn
Metals in the air Particles collected from the air above Mexico City (two shown) contain
metals including manganese, iron, zinc, tin, lead and mercury (labeled above). When inhaled,
these tiny pollutants can travel into the lungs and other parts of the body. New research suggests
that the particles can end up in the brain, where they may cause in;ammation.