Air pollution bad for growing brains and minds: PD and Alz too?

[Guest guest]

Bad air for growing brains and minds

By Bruce Bower

Web edition : Friday, October 10th, 2008

http://www.sciencenews.org/view/generic/id/37515/title/Bad_air_for_growing_brain\

s_and_minds

Mexico City's air pollution may be undermining neural and mental

functioning in some children

Mexico City wears a thick coat of air pollution that clogs lungs and

takes a toll on hearts and blood vessels. But that's just the beginning

--- the metropolis's dirty air may have contributed to brain

inflammation and intellectual deficits in at least some school-age

children, a new study suggests.

Among healthy children aged 7 to 18, lifelong Mexico City residents

scored lower than their peers from Polotitlán --- a Mexican city with

low levels of air pollution --- on tests of memory, flexible thinking,

novel problem-solving skill and the ability to monitor and change one's

behavior during challenging tasks, scientists report in an upcoming

Brain and Cognition. These tests make up part of standard IQ measures

for school children.

What's more, brain scans of many Mexico City youngsters revealed

alterations that can impair the prefrontal cortex, a neural region

heavily involved in memory and thinking skills, say environmental

pathologist Lilian Calderón-Garcidueñas of the University of Montana in

Missoula and her colleagues.

Similar brain alterations, as well as evidence of neural inflammation,

appeared in 1- to 2-year-old dogs that had grown up in Mexico City, the

investigation finds.

Widespread declines in intelligence of the type and magnitude observed

in the new report would have a huge impact on a country's economic

productivity, says psychologist and study coauthor Randall Engle of the

Georgia Institute of Technology in Atlanta. " Saving money by failing to

curb pollution truly is a matter of 'pay me now or pay me later,' " Engle

says.

Although their findings are preliminary, the researchers hope to conduct

a five-year study tracking large groups of children living in areas with

low and high air pollution. The most common air pollutants in Mexico

City are particulate matter, which contains a complex mixture of various

substances, and ozone. Polotitlán's air contains low concentrations of

all major pollutants.

" The growing brain may be vulnerable to the inflammatory effects of air

pollution's fine particulate matter as well as to specific chemicals

that are toxic to brain growth, " comments neuropsychologist Sidney

Segalowitz of Brock University in St. Catharines, Canada.

Children in Mexico City and Polotitlán showed large neural and cognitive

differences that need to be confirmed in further work, remarks

epidemiologist Bellinger of Children's Hospital Boston. The new

study didn't measure the composition of Mexico City air pollution, so

chemical culprits possibly responsible for the results remain unknown,

Bellinger notes. Children's increased lead exposure in Mexico City could

also have contributed to lower scores on mental tasks, he adds.

Blood testing before admission to the study found no differences in

average lead concentrations of Mexico City and Polotitlán children,

Calderón-Garcidueñas says.

She and her coworkers recruited 55 children from Mexico City and 18

children from Polotitlán. All children came from middle class families

and had no serious health problems.

Mexico City kids generally scored lower on specific memory and reasoning

tests than their counterparts did. Using magnetic resonance imaging, or

MRI, on a subset of the children, the researchers observed tissue

alterations typical of inflammation in the brains of 13 of 23 Mexico

City youngsters and 1 of 13 Polotitlán children.

Neural alterations were located near the front of the brain in tissue

that could obstruct nerve transmissions sent to and from the prefrontal

cortex.

In three Mexico City children who received another round of MRI scans 11

months after initial testing, frontal-brain tissue alterations remained

the same.

Calderón-Garcidueñas' team then conducted brain studies of seven healthy

Mexico City dogs and 14 healthy dogs from Tlaxcala, another Mexican city

with low levels of air pollution. All dogs were mixed breeds and had

been reared at animal research facilities.

Comparable inflammation-related tissue alterations in the frontal brain

appeared in four of seven Mexico City dogs and none of the others. In

tissue analyses, brains of Mexico City dogs also displayed particularly

high levels of substances produced by two genes that have inflammatory

effects on the brain.

In studies conducted since 2002, the researchers have reported signs of

brain inflammation and brain disease in dogs exposed to Mexico City's

air. Earlier this year, the researchers found that chronic exposure to

air pollution was associated with markers of brain inflammation and

increased brain immune responses in children and young adults who had

died suddenly and were studied at autopsy. These individuals also

possessed high levels of brain proteins thought to contribute to

Alzheimer's and Parkinson's diseases.

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