Air pollution is one of the world’s most profound issues, it has long been known to cause health problems, be it lung cancer, allergies, heart disease or other respiratory ailments. Human activity and natural processes (harmful substances including Particulates and biological molecules into earth’s atmosphere) can both generate air-pollution. But now the question is — Can dirty air be harmful for a healthy brain?

A new research led by the University of Southern California (USC) scientists and engineers provides new evidence that tiny air pollution particles (Toxic fumes that mainly comes from automobiles and power plants) may greatly increase the chance of dementia, including Alzheimer’s disease. Invisible particles in the air may elevate the risk of dementia by as much as 92%, especially in women with the ApoE4 gene variant (dementia gene), which has been associated with this disease.

The new study, published Tuesday in the journal Translational Psychiatry. Experts and engineers found that those elderly women who living in areas of the United States with fine particulate matter exceeded the US Environmental Protection Agency’s health standards were 81 percent more at risk for global cognitive decline and 92 percent more likely to develop dementia, including Alzheimer’s disease. According to the study, if their findings hold up in the general population, it may have serious implications for the general population. Researchers believe that air pollution in cities could actually be responsible for nearly 21% of memory loss and dementia cases.

“Microscopic particles generated by fossil fuels get into our body directly through the nose into the brain,” said University Professor Caleb Finch at the USC Leonard Davis School of Gerontology and co-senior author of the study.

“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.

“Although the link between air pollution and Alzheimer’s disease is a new scientific frontier, we now have evidence that air pollution, like tobacco, is dangerous to the aging brain.”

For the study, researchers captured polluted air in the major cities such as Los Angeles, California and tracked the cognitive health of women between the ages of 65 and 79 for 10 years, who had the APOE-e4 gene, a genetic variation (that were exposed to air pollution for 15 weeks had 60% more accumulation of beta-amyloid) that is linked to increase the risk for Alzheimer’s disease. Researchers initially found that, for older women, breathing air that is heavily polluted by the detrimental effects of air pollution, which includes fine particulates emitted by power plants, motor vehicles and the burning of biomass products such as wood. “We now know that the major Alzheimer’s risk gene APOE-e4 has an environmental component,” Finch said.

According to researchers, the study is unique in that it found the interaction of APOE-e4 and air pollution may boost brain impairment.

“Our study — the first of its kind conducted in the U.S. — provides the inaugural scientific evidence of a critical Alzheimer’s risk gene possibly interacting with air particles to accelerate brain aging,” said Jiu-Chiuan Chen, co-senior author of the study and an associate professor of preventive medicine at the Keck School of Medicine of USC. “The experimental data showed that exposure of mice to air particles collected on the edge of USC damaged neurons in the hippocampus, the memory center that is vulnerable to both brain aging and Alzheimer’s disease.”

The cognitive effects of pollution are more pronounced in women who carry APOE-e4. Photo Source:-Business Today

The Researchers of the USC (University of Southern California) analysed data from the Women’s Health Initiative Memory Study (WHIMS) regarding 3,647 women aged between 65 to 79 living across 48 states who did not have dementia when they enrolled. The researchers adjusted for each woman’s geographic regions, race or ethnic background, socioeconomic status, lifestyle, education, medical conditions and other factors. The research was a collaboration between USC Davis, the USC Viterbi School of Engineering and the Keck School of Medicine.

The study also identified the offending air pollutants, which are responsible for these damaging effects as tiny, fine and inhalable particles known as PM2.5 with diameters 2.5 µm or less. A human hair is about 70 µm in diameter, making it 30 times larger than the largest PM2.5. The researchers found that those women who lived in high areas of PM2.5 were 81 percent more at risk for global cognitive decline and 92 percent more likely to develop dementia, including Alzheimer’s disease, compared with those women who lived in areas of low PM2.5 concentrations. Scientists believe that reduced PM2.5 levels in the air are associated with fewer cases of dementia, they also found that prolonged exposure to high PM2.5 levels led to loss of white and gray matter volumes in brain regions that process decision-making, planning, and thinking.

Photo Source:-(C. Bickel/Science)

“We analysed data of high PM2.5 levels using standards the EPA set in 2012,” Chen said. “We don’t know whether the lower PM2.5 levels of recent years have provided a safe margin for older Americans, especially those at risk for dementia.”

According to the World Health Organization (WHO), About 48 million people worldwide suffer from dementia, and there are 7.7 million new cases every year. Earlier this year, scientists in Canada found that living close to a main road increases the risk of Alzheimer’s by up to 12%, while Danish researchers found expectant mothers living close to busy roads are at greater risk of serious complications in pregnancy. The scientists tracked the progress of 6 million adults for eleven years found a clear trend with dementia incidence rising the nearer people lived to high traffic/busy roads.

“Our study has global implications as pollution knows no borders,” Professor Caleb Finch said.

Six of the top 10 most polluted cities in the nation by PM2.5 are in California, including Los Angeles, Long Beach, and Fresno, and more cities are becoming gradually more polluted. Less than one-third of all counties in the US have ozone or particle pollution monitors (technology for pollution control), according to the American Lung Association.

Another studies are warranted with people (both genders) to investigate whether air pollution also may affect men, and whether PM2.5 interacts with other pollutants and cigarettes. USC (University of Southern California) researchers and others in this field said more experiment is needed to confirm a causal relationship and to understand how air pollution harms and enters the brain. Accurate pollution monitors are important for this task.

“Many studies have suggested that early life adversities may carry into later life and affect brain aging,” Chen said. “If this is true, then maybe long-term exposure to air pollution that starts a downward spiral of neurodegenerative change in the brain could begin much earlier and rev up in later life.”


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