How Air Pollution Affects Eye Health

Medical News: Air Pollution and Eye Health: An Emerging Concern
In recent years, the link between air pollution and health issues has gained substantial attention. While much of the focus has been on respiratory and cardiovascular problems, researchers from Pusan National University in Korea have uncovered significant impacts on ocular health. Specifically, particulate matter (PM), or tiny particles suspended in the air, can lead to various eye disorders. This Medical News report examines how exposure to PM contributes to conditions such as dry eye disease, conjunctivitis, pterygium, and even severe retinal disorders.


How Air Pollution Affects Eye Health
Image: AI-Generated
 
What is Particulate Matter?
Particulate matter, often labeled as PM2.5 or PM10 based on particle size, originates from sources like vehicle emissions, industrial processes, and even natural sources like dust. PM2.5 particles, being very fine, are particularly hazardous since they can penetrate deep into the body, reaching the lungs and other organs through blood circulation. While PM2.5 has long been associated with respiratory and cardiovascular diseases, recent studies reveal it also significantly affects the eyes.
 
Key Findings on Particulate Matter’s Impact on Eye Health
-Ocular Surface Diseases: A Widespread Issue
The eye’s surface, which includes the cornea and conjunctiva, is directly exposed to the environment, making it vulnerable to air pollutants. Studies show that people exposed to high levels of PM experience symptoms such as redness, itching, and a burning sensation. Prolonged exposure leads to dry eye disease (DED), where the tear film becomes unstable, causing discomfort and potential damage to the eye’s surface. A study involving 43 participants in Korea found that PM exposure decreased tear break-up time, a key indicator of DED, and increased the ocular surface disease index score.
 
-Conjunctivitis: Inflammation of the Eye's Outer Layer
Conjunctivitis, often linked with allergens like pollen, can also be aggravated by particulate matter. Symptoms include redness, itching, and a feeling of grittiness. Research shows that PM exposure above 10 µg/m³ is associated with a rise in conjunctivitis cases. Animal studies support these findings, showing that PM exposure can trigger inflammatory responses, leading to conditions similar to allergic conjunctivitis. Such studies reveal increased levels of inflammatory markers in the conjunctiva and cornea.
 
-Pterygium: An Overlooked Consequence of Air Pollution
Pterygium is a condition where a benign growth of tissue encroaches on the cornea. Though primarily associated with UV exposure, researchers have observed a link between pterygium prevalence and high levels of air pollution. A study conducted in Korea found that individuals exposed to elevated PM levels were more likely to develop this condition. Researchers believe oxidative stress and inflammation caused by fine dust are significant contributors.
 
-Retinal Disorders: Damage Beyond the Eye Surface
The retina, located at the back of the eye, is responsible for capturing light and transmitting visual information to the brain. Experimental studies show that PM can damage the retinal pigment epithelium (RPE), a layer that supports the retina’s function. In one study, researchers observed that PM exposure increased retinal vascular permeability and inflammation in the RPE cells. PM2.5 exposure was also linked to increased retinal thickness, which could lead to vision problems. Interestingly, exposure to PM can also impair retinal development, as shown in studies using embryonic stem cell-derived retinal organoids.
 
-Glaucoma and Cataract: Emerging Links
While the connection between PM and glaucoma is still under investigation, there is growing evidence of a link. In a large-scale study involving over 33,000 adults, exposure to PM2.5 was associated with an increased risk of glaucoma.
 
Researchers speculate that PM might contribute to intraocular pressure changes or nerve damage through oxidative stress and inflammation.
 
Mechanisms Behind PM-Induced Ocular Damage
Studies suggest that PM triggers several pathological processes that lead to ocular damage:
 
-Oxidative Stress: Particulate matter contains metals and chemicals that generate reactive oxygen species (ROS). Excessive ROS production damages cells, leading to oxidative stress. In studies on corneal cells, PM exposure increased ROS levels, which caused DNA damage and cell aging.
 
-Inflammation: PM exposure activates inflammatory pathways in the eye. The MAPK/NF-κB signaling pathway, responsible for immune responses, becomes highly active in PM-exposed cells. Elevated levels of pro-inflammatory cytokines have been detected in corneal and conjunctival tissues after PM exposure, which can lead to conditions like conjunctivitis and dry eye disease.
 
-Autophagy: In response to PM, cells may initiate autophagy, a process where they attempt to remove damaged components. However, in cases of chronic exposure, this process can become harmful. Research has shown that PM2.5 exposure induces excessive autophagy in corneal cells, leading to cell death.
 
-Cell Death: Continuous PM exposure leads to various forms of cell death, including apoptosis (programmed cell death) and ferroptosis (iron-dependent cell death). Studies on retinal cells show that PM exposure can increase apoptosis, potentially leading to retinal thinning and vision loss.
 
Limitations and Future Directions
Although substantial progress has been made in understanding PM’s impact on ocular health, challenges remain. Epidemiological studies, for instance, often rely on atmospheric PM measurements that vary based on climatic and geographical factors, potentially affecting study outcomes. More controlled experimental studies are necessary to explore therapeutic strategies, such as antioxidants or anti-inflammatory agents, that may mitigate PM’s harmful effects on the eyes.
 
Conclusion
The findings from Pusan National University underscore the urgency of addressing air pollution’s impact on eye health. As PM levels continue to rise globally, public health initiatives should consider eye health in air quality regulations. Preventive strategies, such as wearing protective eyewear and using air purifiers, may also help individuals minimize their exposure to harmful particles. Continued research and collaboration across fields are essential to developing treatments and preventive measures that safeguard ocular health in an increasingly polluted world.
 
The study findings were published in the peer-reviewed International Journal of Molecular Sciences.
https://www.mdpi.com/1422-0067/25/22/12107
 
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