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Study: Age-related macular degeneration risk doubles when exposed to vehicle exhaust pollutants

From lung cancer to premature death, exposure to pollutants has been linked to a heightened risk of chronic diseases and their related health complications. Now recent research published in the BMJ Journal of Investigative Medicine adds another troubling pollution-related risk: Age-related macular degeneration (AMD), a chronic disease that can lead to irreversible vision loss.

Scientists from China Medical University (CMU) Hospital in Taiwan documented for the first time that the prolonged exposure to major air pollutants from vehicle exhaust, including nitrogen dioxide and carbon monoxide, is linked to a raised risk of AMD in older adults.

Major pollutants in vehicular exhaust can raise the risk of AMD

To determine if major traffic-related air pollutants like nitrogen dioxide and carbon monoxide had detrimental effects on eye health, the team of scientists analyzed air quality and the health insurance data of 39,819 participants aged 50 and older from 1998–2010.

Thirty percent of the participants had been living in highly urbanized areas in Taiwan and another 32.5 percent had been living in moderately urbanized areas.

The team divided the participants into four categories based on their level of pollutant exposure.

During the monitoring period, the team found that 1,142 of the participants developed AMD. It also appeared that participants living in areas that had the highest concentrations of nitrogen dioxide and carbon monoxide also had the highest risk of AMD.

In addition, participants that had been exposed to the highest levels of nitrogen dioxide had almost double the risk of the disease.

On the other hand, participants exposed to the highest levels of carbon monoxide had an 84 percent increase in their risk of developing AMD compared to those in areas that had less than moderate levels of either pollutant. Moreover, none of the participants living in these areas had a raised risk of AMD.

But despite these interesting findings, the team emphasized that their research does not establish prolonged exposure to traffic-related air pollutants as a definite cause of AMD since their data did not include other risk factors for the disease, such as smoking, genetics and the presence of inflammation.

Fernando Arevalo, a professor of ophthalmology at the John Hopkins University School of Medicine in Baltimore, who was not a member of the research team, echoed this, adding that the observational nature of the research can establish an association but not a cause and effect relationship among the variables involved.

Arevalo noted that further studies are needed because numerous genetic and environmental factors besides age and air pollution also have a hand in the development of AMD.

In addition, Avnish Deobhakta, an assistant professor of ophthalmology at the Icahn School of Medicine at Mount Sinai in New York, noted that, based on the research findings, inhaled pollutants might have the same effect as smoking, the single most controllable risk factor for AMD.

Exposure to air pollution can trigger inflammation, a risk factor for AMD

Prior to this research, there hadn’t been much evidence to suggest that air pollution can affect more than just the risk of lung cancercardiovascular disease and other similar chronic conditions.

That said, scientists have good reason to believe that exposure to air pollution can lead to inflammation. In fact, the role of air pollution in inflammation has been the subject of numerous studies in the past.

One such study, recently published in the Journal of Allergy and Clinical Immunology, established that exposure to particles derived from combustion processes like diesel exhaust can trigger inflammation responses.

In particular, ultrafine particles from vehicle emissions can get in through the nose or the mouth, breach the lung barrier, enter the bloodstream and penetrate organs, thus causing health complications. (Related: Air pollution found to damage your health on a CELLULAR level.)

Additionally, a recently published study by scientists from the University of Eastern Finland and the University of Lodz in Poland underscored the role of inflammation in the pathogenesis, or development, of AMD.

Taken together, these recent studies, including the BMJ Journal of Investigative Medicine research, contribute to an emerging body of evidence that exposure to air pollution might heighten the risk of AMD, if not trigger its onset altogether.

Learn more about the potential chronic health effects of air pollution at

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