Expert Commentary

Air pollutants from automotive traffic act on glutamatergic neurons

2011 study in Environmental Health Perspectives on responses in rodent brains to particulate matter from highway traffic.

Numerous studies have shown that automotive pollution has a wide range of negative health effects, including heart and lung disease. Much of the blame has been pinned on gases such as carbon monoxide, nitrogen dioxide, sulphur dioxide and ozone, but the role of suspended particulate matter has been less clear.

Particulate matter released by automotive traffic is literally microscopic — it ranges in size from 20 to 200 nanometers — and passes easily through air-filtration systems and into passenger compartments. The particles are the result of the wear of components such as tires and belts, and include polycyclic aromatic hydrocarbons and carbon black, a known carcinogen.

In a 2011 study published in Environmental Health Perspectives, “Air Pollutants Act on Glutamatergic Neurons,” researchers at the University of Southern California used rodents to measure the impact of particulate matter on neurobiology and brain health. Traffic-related air pollution was simulated through the collection of material from roads that was then filtered, suspended in liquid and re-aerosolized.

The study’s findings include:

  • Neuron function and growth was adversely affected after chronic inhalation of particulate matter in simulated freeway air by adult mice for 10 weeks. More targeted in vitro experimentation on brain tissue showed the same effect after just 48 hours of exposure.
  • After 48 hours of direct exposure, neurons vulnerable to cerebral ischemia showed increased propidium iodide, an indicator of cell death. Additionally these cells showed signs of inflammation associated with premature aging and Alzheimer’s.
  • Neurons from developing mice did not grow as well and the impairments were consistent with prior evidence of the developmental effects of air pollution in children including an association with autism.

Such particles, while not visible, “have an effect on brain neurons that raises the possibility of long-term brain health consequences of freeway air,” a researcher stated.

In addition, because a significant portion of suspended particulate matter is from wear on car parts rather than fuel combustion, even a society-wide switch to electric vehicles wouldn’t eliminate the problem. While this would “sharply decrease the local concentration of nanoparticles,” the researcher noted, “at present, electrical generation still depends upon other combustion processes — coal — that in a larger environment contribute nanoparticles.”

Keywords: carbon black, coal, fossil fuels, pollution, cars, California

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