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Air pollution is a global public health issue. A new study conducted by Inserm researchers points to the harmful effects on health of fine particles emitted by thermal vehicles. In particular, they would promote the development of glaucoma.

According to a study by Inserm and the University of Bordeaux published in the journal Environmental Researcha exposure extended to fine particles, in particular those produced by road traffic, would promote ocular aging and could lead to glaucoma. This neurodegenerative disease is the second cause of blindness in the world. It damages the nerve endings of the optic nerve in the retina, which causes a progressive impairment of the field of vision.

In this new study, the researchers found that people who were more exposed to pollution showed faster thinning of the retinal nerve layer over the years. Pollutants would promote the deterioration early retinal cells, signifying faster aging of the eyes.

Research that measures the effects of air pollution

The researchers followed 683 people, aged over 75, residing in Bordeaux. Follow-up took place over ten years, between 2009 and 2020. Participants had eye exams every two years to track changes in retinal nerve fiber thickness and thus indirectly determine how quickly their eyes were getting old. At the same time, the scientists estimated the exposure of these people to pollution atmospheric through measurements of the concentration of different air pollutants with an accuracy of 100 meters around their place of residence. These data were obtained using annual exposure maps based on measurements from air quality monitoring stations. Among the pollutants taken into account: nitrogen dioxide and two types of fine particlesthose with a diameter of less than 2.5 microns, “PM2.5”, and soot carbon (a major fraction of particles resulting from the incomplete combustion of fossil fuels and biomass).

For your information, air pollution is a mixture of gases and particles suspended in the air, resulting mainly from the incomplete combustion of fossil fuels.

Fine particles: pollutants very harmful to health

Through this study, the researchers found that people who were exposed to higher concentrations of fine particles had a refinement nerve layer faster retinal over the years. This refinement is one of symptoms precursors of glaucoma.

The very small size of fine particles allows them to penetrate deep into the body and cause inflammatory reactions and oxidative stress in the body. Laure Gayraud, doctoral student in epidemiology and first author of the study, points out: This is thought to be the mechanism at work in this study. : fine particles could penetrate the barrier of the retina and cause degeneration of ocular cells.” The smallest fine particles can even pass through the vessels and end up in the bloodstream.

“Exposure to high concentrations of pollutants could lead to an acceleration of neurological aging”

Cécile Delcourt, research director at Inserm, the last author of this work, specifies: ” Our study documents the effects of air pollutants on the neurological aging. Taking the example of ocular aging, she suggests that exposure to high concentrations of pollutants over time could lead to an acceleration of neurological aging, as observed in studies on brain aging..”

“The effective exposure of the French population [à la pollution] continues to exceed the current regulatory thresholds in places “

Doctoral student Laure Gayraud warns that all the participants in this study were exposed to pollution levels below the recommended threshold: “We were between 16 and 25 micrograms. Currently, the European regulatory threshold is 25 micrograms per cubic meter.She emphasizes the importance of this study: It constitutes an additional argument in favor of lowering the European regulatory thresholds, as recommended by the WHO, as well as reducing the effective exposure of the French population, which continues to exceed by place the thresholds current regulations.The thresholds advised by the WHO in 2005 were 10 micrograms and in 2021 they were lowered to 5 micrograms.

The objective for the scientists is to broaden the field of study on a national scale, in order to deepen knowledge of the effects of pollutants on ocular aging.

Can glaucoma be cured?

Glaucoma is a disease that cannot be cured but for which it is possible to control the evolution by preventing it from progressing and getting worse. Once glaucoma has been diagnosed, you will need lifelong monitoring.

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