Prolonged exposure to particulate matter in air pollution in the Los Angeles Basin triggered inflammation and the appearance of cancer-related genes in the brains of rats, a Cedars-Sinai study has found.

Air pollution is linked to brain inflammation, which accelerates tumorigenesis and neurodegeneration. The molecular mechanisms that connect air pollution with brain pathology are largely unknown but seem to depend on the chemical composition of airborne particulate matter (PM).

While previous research has documented the association between air pollution and a variety of diseases, including cancer, the study found markers indicating certain materials in coarse air pollution, nickel, in particular, might play a role in genetic changes related to disease development, said Julia Ljubimova, MD.

Ljubimova, director of the Nanomedicine Research Center at Cedars-Sinai, is the lead author of the paper, published April 9 in Scientific Reports. "This study, which looked at novel data gathered in the Los Angeles area, has significant implications for the assessment of air quality in the region, particularly as people are exposed to air pollution here for decades," Ljubimova said.

The study found that coarse particulate matter in the region's air pollution found its way into bodily systems in two ways: inhaled through the lungs, where trace metals and other materials enter the bloodstream and then the brain; and through the nose, where the materials are absorbed more directly into the brain.

Inflammation and Cancer-related genes

Rats in all experimental groups, including those exposed to filtered air, had detectable levels of Ni, Co, and Zn in their brains. The researchers found a transient upregulation of IL16 and IL-13Rα1. Tissue expression of IL16 recruits and attracts a variety of immune response cells, including monocytes and dendritic cells

"Cleaning the air in the Los Angeles Basin has been a long and arduous task, and we are happy to support the research that produced such a groundbreaking paper," said William A. Burke, EdD, chairman of the South Coast Air Quality Management District. "We must continue to shed light on how air pollution negatively affects our health."

Ljubimova noted that while the study's findings might be unique to the composition of air pollution in the Los Angeles Basin, "There are many examples of potentially damaging effects of air pollution exposures in major cities," said Ljubimova.

"Our modern society is becoming increasingly urbanized and exposed to air pollution. This trend underscores the need for additional research on the biology of air-pollution-induced organ damage, along with a concerted effort aimed at reducing ambient air pollution levels," said Ljubimova.

The data show that PM-induced toxicity is caused by synergistic effects of metals and toxins that are uniquely present in some PM types. The findings might be unique to the Los Angeles Basin and might depend heavily on the air pollution composition in this region.