Beyond its environmental effects, air pollution is known for being harmful to the respiratory and circulatory systems. Toxic air pollutants like sulfates, nitrates, and black carbon can penetrate deep into lung and cardiovascular tissues, which poses a serious risk to human health. Outdoor air pollution is regarded as the top single killer in the world -- causing up to 3 million deaths per year.
Now, new research has shown that the hazardous effects don't stop there: air pollution is bad for the brain, too. The study, led by researchers from the University of Southern California, found that air pollution raises the risk of dementia by up to 92 percent -- thanks to toxic particles that cause brain swelling. Even if the air doesn't kill you, it will make you sick one way or another.
The toxic fumes from cars and power plants are actually infiltrating brain cells, which leads to swelling. In turn, this leads to an increased risk of dementia, experts say. In fact, air pollution may actually be behind the rising incidence of dementia. Epidemiologist Jiu-Chiuan Chen of the Keck School of Medicine at USC, the study's lead author, says that if their findings hold up for the rest of population, it would suggest that air pollution is related to about 21 percent of all dementia cases across the world.
The Californian research team analyzed data from 3,647 women who were between the ages of 65 and 79, and did not have dementia. Their 11-year epidemiological study was the first of its kind to be conducted in the United States and was published by the journal Translational Psychiatry. [Related: Learn more about the latest scientific research at Scientific.news]
What the researchers found was that women who lived in heavily polluted areas, such as near main roads or in busy cities, had a dramatic increase in their risk for cognitive decline -- to the tune of 81 percent. Being exposed to levels of pollution deemed unsafe by health officials also translated to a 92 percent greater risk of developing dementia.
The team also discovered that certain women may be more at risk than others. Women who carried the APOE4 gene -- which increases the risk of Alzheimer's disease -- exhibited the highest risk of getting dementia.
Professor Caleb Finch, who co-authored the study, explained, "Microscopic particles generated by fossil fuels get into our body directly through the nose into the brain."
"Cells in the brain treat these particles as invaders and react with inflammatory responses, which over the course of time, appear to exacerbate and promote Alzheimer's disease."
Finch says that while the link between air pollution and Alzheimer's disease and other types of dementia is still a "new frontier," evidence continues to show that pollution is harmful to an aging brain. [Related: Keep up with the latest headlines about healthy aging at Longevity.news]
Previous research has also shown a correlation between air pollution and dementia risk. For example, earlier this year Canadian researchers unveiled their own findings that suggested air pollution is harmful to the brain. The team found that living within 50 meters of a main road were 12% more likely to develop dementia. In such close proximity, the levels of fine pollutant particles are up to 10 times higher than they are at even just a slightly further distance of 150 meters.
In 2015, an analysis of MRI brain scans from individuals that had enrolled in the Framingham Heart Study also came up with some concerning findings. The researchers from Harvard Medical School discovered that the closer people lived to a major roadway (and the more pollution they'd been exposed to), the smaller their cerebral brain volume was. This association remained even after the scientists adjusted for other factors like smoking, diabetes, and cardiovascular disease.
While the study of air pollution's effects on the brain may be new, these recent findings certainly demand attention.