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Chronic exposure to high levels of air pollution may be linked to cognitive performance.
This is the conclusion of an investigation carried out in China, which indicates that the damaging effect of toxic air on society is much deeper than previously suspected.
According to the researchers – from Peking University, in China and Yale University, in the United States, among others – the negative impact increases with age and affects more men with low levels of education.
The study, which spanned four years, focused on the verbal and mathematical abilities of 20,000 men and women of different ages in China.
Scientists believe that the results have global relevance, since more than 90% of the world’s urban population lives in environments where air pollution exceeds the limits considered safe by the World Health Organization.
Despite establishing a link between pollution and poor results in language and math tests, the study does not prove a cause-and-effect relationship.
The investigation was based on measurements of sulfur dioxide, nitrogen dioxide and particles with a diameter smaller than 10 micrometers taken in the area where the study participants lived.
It is not clear how much each of these elements contributes to the problem.
Carbon monoxide, ozone and larger particles were not included in the study.
The most vulnerable
Described as an “invisible killer”, air pollution causes about seven million premature deaths annually in the world , according to the WHO.
“We have evidence that the effect of air pollution on verbal tests becomes more pronounced as people get older, especially in men and people with less education,” says the study published in the journal Proceedings of the National Academy of Sciences .
Pollution, the study suggests, increases the risk of developing degenerative diseases such as Alzheimer’s and other forms of dementia.
“Our samples allow us to examine the impact of air pollution as people age, and our results (on impact) in the process of life are quite novel,” explained Xi Chen, of the School, to the BBC. Yale Public Health.
As part of the study, the researchers analyzed the examinations of people of both sexes, from 10 years onwards, between 2010 and 2014.
Participants had to answer 24 basic math questions and 34 word recognition questions.
Previous studies had already found that pollution had an impact on students’ cognitive abilities.
“This latest study coincides with previous research,” explains Derrick Ho of the Hong Kong Polytechnic, who has worked on the health effects of extreme weather events such as haze.
“What is new in this study is the focus on China and the fact that it is very detailed compared to many other studies,” the scientist told the BBC.
“The differentiation in terms of gender and age is also new.”
It is estimated that many pollutants directly affect brain chemistry in several ways. For example, particulate matter can transport toxins through small passages and enter the brain directly.
Some pollutants can also have a psychological impact (they can increase the risk of depression).
Air pollution in the world
- Nearly 7 million people die each year due to exposure to contaminated air
- Air pollution caused 4.2 million deaths in 2016
- 91% of the world population lives in places where pollution exceeds the limits recommended by WHO
- Of the 20 most polluted cities, 14 are in India
- 9 out of 10 people breathe contaminated air
One of the reasons why researchers believe that older men with less education are the most affected by chronic exposure to air pollution is that they usually do manual labor in the open air .
“Our results on the damaging effect on cognitive abilities, especially in the aging brain, imply that the indirect effect on social well-being can be much broader than previously thought,” the researchers say.
“For the elderly (those over 55) the effects can be very difficult to mitigate given the accumulation of long-term exposure,” says Xi.
“This is very worrying because we all know that people often have to make important financial decisions in old age, such as when to retire, which health coverage plan is better …”.
The study indicates that while its focus was on China, the results may shed light on the situation in other developing countries with severe air pollution problems.