Long term exposure to pollutants from vehicle exhaust is linked to a heightened risk of the common eye condition -- age-related macular degeneration or AMD, says researchers.

AMD is a neuro-degenerative condition that affects the middle part of the retina, known as the macula. It is one of the most common causes of poor vision in older people and is most likely caused by an interplay between genetic and environmental risk factors. The study, published in the Journal of Investigative Medicine, shows that exposure to the highest levels of air pollutants was associated with an almost double risk among those aged 50 and older.

For the study, the researchers from Asia University in Taiwan analysed national health insurance and air quality data from 1998 to 2010 to see if there might be a link between long term exposure to the pollutants nitrogen dioxide and carbon monoxide and a heightened risk of AMD. As the condition is more common among older age groups, the researchers focused on 39,819 people aged 50 and above.

During the monitoring period, a total of 1,442 people developed cases of AMD. Those with the highest level of exposure to nitrogen dioxide were nearly twice as likely (91 per cent) to develop AMD than those exposed to the lowest level. Those exposed to the highest level of carbon monoxide were 84 per cent more likely to develop AMD than those exposed to the lowest levels.

According to the researchers, this study has implicated nitrogen dioxide in cardiovascular and neurological ill health and as the retina is part of the central nervous system, there is a plausible biological explanation for its vulnerability to this pollutant.