Prolonged exposure to nitrogen dioxide and carbon monoxide can increase risk of age-related macular degeneration that can cause irreversible visual impairment
Long-term exposure to traffic-related pollutants — nitrogen dioxide (NO2) and carbon monoxide (CO) — is associated with a higher risk of developing age-related macular degeneration (AMD), a progressive disease that can cause irreversible visual impairment, according to a recent study.
The study analysed air quality and health insurance data of 39,819 residents between 2000 and 2010, living in urban areas of Taiwan, aged 50 years or older and who did not have AMD upon enrollment.
The research team led by Suh-Hang Hank Juo, from the Center for Myopia and Eye Disease at China Medical University in Taiwan, and his colleague divided the participants into four categories of pollution exposure.
After an 11-year follow up, 1,442 participants showed the highest rate of disease, according to the study published in BMJ Journal of Investigative Medicine.
Those living in areas with highest concentration of NO2 and CO showed the highest rate of AMD — long-term exposure to the highest quartile of NO2 (concentration greater than 9825.5 parts per billion) significantly increased the risk for AMD by almost two-fold even after adjusting for potential confounding factors.
Similarly, exposure to the highest quartile of CO (less than 297.1 parts per billion) also increased the risk for AMD by 84 per cent.
Areas with low NO2 exposure had the lowest incidence of AMD (2.8 per cent), while those with high NO2 exposure showed the highest incidence (5.4 per cent).
The demographic data according to the CO exposure levels showed a similar trend. The highest rate (5.8 per cent) of newly diagnosed AMD was among people living in areas with inreased CO exposure.
AMD is a late-onset disease characterised by the formation of lipid-rich extracellular deposits, localised inflammation and ultimately neurodegeneration in the central part of the retina (termed the macula).
NO2 has been associated with various brain diseases, including low cognitive function and a lower functional integration in children, Parkinson’s disease, stroke and dementia.
Retina, which is considered a part of the central nervous system, is also “biologically reasonable to be vulnerable to NO2 intoxication”, the study noted.
The disease has increasingly become a global issue, particularly among the Asian population over 50 years.
This is the first such study, which documents AMD's relation and exposure to both NO2 and CO air pollutants. Overall, there has not been much debate on the effect of air pollution on eye diseases.
Most environment pollutants do have an effect on eyes and it is high time it is recognised, said Radhika Tandon, professor of Ophthalmology at All India Institute of Medical Sciences (AIIMS) in New Delhi.
She added that there is no reason to believe that the results from the Taiwan study, if extrapolated for India would be drastically different. Other effects of traffic pollution includes dry eye, conjunctivitis, eye allergies.
“Such cases have increased manifold in the last decade. On an average, AIIMS sees 50-100 such cases in a week,” Tandon said.
The institute is also conducting its own study to know the impact of air pollution and ultraviolet radiation exposure on the health of eyes in urban population of Delhi.
Around 12,000 people are being screened for the study, which is taking into account primary pollutants like particulate matter (PM) 2.5 and PM10, aerosol, NO2, sulphur dioxide, CO along with sun exposure and will also look at geographical location and local individual factors.
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