Page 486 - Environment: The Science Behind the Stories

7–8 from Mexico City with 10 simi-
Cough 20%
lar children from a Mexican city with
Nasal clean air, measuring their cognitive
obstruction skills and scanning their brains with 15%
Nasal magnetic resonance imagery (MRI).
dryness 10%
Results showed that the Mexico City Percent change in likelihood of death
Chest children performed more poorly on
discomfort most cognitive tests of reasoning, 5%
Nasal knowledge, and memory. The differ-
lesions 0%
ences in cognition were consistent
Scabbing with differences in volume of white –5%
mucus Lowest Highest
matter in key portions of the brain as
0 25 50 75 100 revealed by the MRIs. Concentration of
Percentage of children Pollution even damages the sense particulate matter
showing symptoms (a) Death rates increase with
of smell. In 2006–2008 Robyn Hudson pollution intensity
Figure 1 Most Mexico City children and colleagues ran lab experiments
show respiratory symptoms from air pol- comparing Mexico City residents with 10
lution. Similar children from less-polluted residents of a geographically similar
areas outside Mexico City show none rural region with clean air. Hudson’s 8
of these conditions. Data from Calderón- team presented the subjects with 6
Garcidueñas, L., et al., 2003. Respiratory damage various smells at different intensities.
in children exposed to urban pollution. Pediatric Compared with the rural residents, 4
Pulmonology 36: 148–161. Mexico City residents had trouble Percent change in likelihood of death 2
smelling distinct and familiar scents 0
such as orange juice and coffee. They –2
Mexico City who had died at an early also struggled to distinguish between
age. They found that pollution exacts the common Mexican beverages –4
a toll before the age of 18 and that horchata and atole. The city-dwellers –6
tiny bits of dead bacteria that cling even had trouble noticing the stench 0 1 2 3 4 5
to pollutant particles are part of the of rotting food! The researchers Days after severe
problem. The heart mounts an inflam- attributed this to tissue damage in the pollution episode
matory response to try to repel the noses of city-dwellers from a lifetime (b) Infant mortality rates are higher
bacteria-laden particles, but because of exposure to pollutants. Indeed, after a pollution episode
the pollution is persistent, the inflam- other scientists were documenting Figure 2 rates of (a) death and
mation becomes chronic and stresses such tissue damage with electron (b) infant mortality each increase in
the heart. microscopy. Mexico City with the intensity of air CHAPTER 17 • AT m os PHER i C sC i E n CE , Ai R Qu A li T y, A nd Poll u T i on Con TR ol
Recent research also shows that All these impacts can lead to pollution. Data from (a) Borja-Aburto, V., et al.,
air pollution affects children’s brains, higher rates of death. Studies by a 1997. Ozone, suspended particulates, and daily
sometimes leaving damage in brain U.S. and Mexican research team mortality in Mexico City. Am. J. Epidemiology
tissue that is similar to that seen in in Mexico City in the late 1990s 145: 258–268; and (b) Loomis, D., et al., 1999.
Alzheimer’s disease. In one study using confirmed this by comparing death Air pollution and infant mortality in Mexico City.
brain scans, Calderón-Garcidueñas certificate records against air pollution Epidemiology 10: 118–123.
and her colleagues found that 56% of measurements. The team found that
Mexico City youth had lesions on the death rates rose on the day of and the The extensive research showing
brain’s prefrontal cortex, whereas fewer day after severe pollution episodes, a diversity of health impacts from air
than 8% did in a region with clean air. especially in response to particulate pollution in Mexico City has caught the
Studies elsewhere, from Italy to Boston, matter (Figure 2a). They also found that attention of city leaders. These scientific
are finding similar results. infant mortality was significantly higher findings have helped push them to
In 2011, Calderón-Garcidueñas’s in the days following strong pollution work hard toward cleaning up their
team compared 20 children aged episodes (Figure 2b). city’s air.

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