Environmental Protection

Mexico City Air Pollution Shows Adverse Effects at Young Age

A post-mortem study of the hearts of 21 young people in Mexico City has found that the heart begins to show the adverse effects of air pollution at a young age and that tiny bits of inactivated bacteria that hitch a ride on pollutants may make the problem worse.

The study contrasted two different areas of the same city, showing that different types of pollutants can produce different effects.

Rodolfo Villarreal, Juan Palacios, Keith Parker and Lilian Calderon carried out the study, “Gene inflammatory expression profiling in right versus left ventricles in young urbanites: What is the long-term impact of myocardial inflammation in the setting of air pollution?” They will present their findings in a poster session today at the Experimental Biology 2010 conference in Anaheim, Calif. The researchers are from the University of Montana (Palacios, Parker, Calderon), the Instituto Nacional de Pediatria in Mexico City (Calderon) and the Big Sky High School in Missoula, Mont. (Villarreal). The American Society for Investigative Pathology is sponsoring the poster presentation.

The researchers examined the hearts of 21 young adults, average age 18, who had lived in Mexico City before dying in accidents. Mexico City has some of the worst air pollution in North America and has high concentrations of microscopic pollutants, known as particle pollution, or particulate matter.

Endotoxins are bits of dead bacteria that can gain entrance to the body by attaching to particulate matter. The bacteria are from a variety of sources, including feces and soil. The bacterial bits that hitchhike on particulate matter are remnants of the bacterial cell wall and are composed of lipopolysaccharides.

The body reacts to the particulate matter and endotoxins by mounting an inflammatory response, which is the body’s attempt to remove foreign invaders. Because the pollution is chronic, this can lead to chronic inflammation in the affected organs, such as the heart. Air monitoring in metropolitan Mexico City has shown that pollution characteristics differ between north Mexico City and south Mexico City. Residents in the south side are exposed to higher levels of endotoxins than residents of north Mexico City. The research team’s previous research found that mice exposed to air from south Mexico City had higher levels of inflammation in the heart muscle than mice exposed to north Mexico City air. They hypothesized that the difference could be linked to the difference in endotoxin levels.

The researchers wanted to see if the residents of north and south Mexico City were also affected differently, as the mice had been. They studied heart samples of young people who had died in accidents ─ six from south Mexico City and 15 from north Mexico City. Their average age at the time of death was 18 years, with most falling in the range of 13 to 23 years.

The study found that residents of both north and south Mexico City showed signs of inflammation in the heart. But residents in the south had a stronger inflammatory response.

The researchers concluded that:

  • polluted air can create inflammation, even in the hearts of young individuals;
  • the right ventricle responds differently than the left; and
  • endotoxins play a role in the inflammation.

“As people age, this chronic inflammation may become a factor in heart disease,” said Villarreal. “The bottom line is, the air we breathe affects our heart health. The more research is conducted in this field, the more it is becoming clear we need to address the issue of air quality and its intricate ties to our health.”

The American Society for Investigative Pathology is a society of biomedical scientists who investigate mechanisms of disease.

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