Extended exposure to pollutants commonly found in vehicle exhaust can be linked to a heightened risk of the eye condition known as age-related macular degeneration (AMD), according to peer-reviewed study.

AMD is one of the most common eye conditions for older age groups, and it can be influenced by both genetic and environmental factors, the study published online in the Journal of Investigative Medicine says. The disease affects the middle of the retina, which is called the macula.

The study, conducted by researchers in Taiwan, looked at 39,819 people aged 50 and above-a majority of which lived mostly in either highly or moderately urbanised areas. Researchers used data from national health insurance and air quality monitoring from 1998 to 2010.

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.

Prolonged exposure to nitrogen dioxide and carbon monoxide has long been associated with cardiovascular and respiratory diseases, but this study is the first to associate the pollutants with AMD. A high level of nitrogen dioxide is also associated with brain diseases such as stroke or dementia. The study noted that the retina is also connected to the central nervous system making it °biologically reasonable to be vulnerable to nitrogen dioxide intoxication.

In July, the Environmental Protection Agency issued a warning for Dublin, citing nearly a dozen testing stations in the city where the nitrogen dioxide levels exceeded the annual limits established by the EPA.

AMD is the leading cause of sight loss for those in Ireland over the age of 50, and it is the leading cause of legal blindness if not treated-affecting 60,000 Irish people-according to the Irish College of Ophthalmologists website.

The study was observational, meaning the results can’t definitively establish cause. The researchers also note that additional risk factors, such as smoking or genetics, were not included in the data.