Research carried out by Dong Hyun Kim, M.D., of Gachon University Gil Medical Center, Incheon, Korea and colleagues has shown a link between outdoor air pollution and dry eye disease. The study is published online by JAMA Ophthalmology.
There are many health risks posed by air pollution, and according to the World Health Organization (WHO), most of that pollution is comprised of ozone, nitrogen dioxide, and sulfur dioxide. These pollutants are especially damaging to the respiratory and cardiovascular systems. New research, however, is beginning to show that air pollution affect the eyes, as well. Certain types of ocular surface abnormalities have been thought to be related to dry eye disease (DED), but there haven't been any large scale studies performed to substantiate that belief.
This study, however, has shed new light on the subject. The Korea National Health and Nutrition Examination Survey collected data from 16,824 participants between January of 2010 through December 2012. For the purpose of the study, DED was defined as previously diagnosed by an ophthalmologist or the presence of frequent ocular pain and discomfort, such as feeling dry or irritated. Information was collected from 283 national monitoring stations across South Korea pertaining to various air pollution measurements. The pollutants included average annual humidity, particulate matter with aerodynamic diameter <10 µm [PM10], ozone, and nitrogen dioxide levels.
With this information, researchers discovered that lower levels of humidity and higher levels of ozone were associated with DED. This result takes into account certain risk factors, like gender, dyslipidemia, thyroid disease, subjective health awareness, and previous ocular surgery. While there may be a correlation between the pollutants and the people suffering from DED, there's not yet enough information to form a cause-and-effect relationship between the two sets of data.
From the listed pollutants monitored in the study, PM10 was ruled out as being a contributing factor to DED. Researched hypothesize that as the particulate matter comes in contact with the ocular surface, reflex tearing may flush it from the eye. Alternatively, PM10 levels in South Korea may not be high enough to induce negative effects on the eye. More studies in other areas of the world are needed to make that determination.