Pollution is linked to glaucoma, conjunctivitis, and even myopia

Pollution is linked to glaucoma, conjunctivitis, and even myopia

In 19th-century London, when Charles Dickens wrote that “the fog was thick and dark,” people were advised to wear special fog glasses while in smog to avoid “clever eyes.” Recent research shows that such recommendations were on to something: Dirty air can damage our eyesight.

It can lead to cataracts, glaucoma (the second most common cause of blindness), conjunctivitis, age-related macular degeneration, and even increase the risk of having to wear glasses. While research shows that such effects are most pronounced in highly polluted cities in Asia, studies conducted in North America and Europe have found that even lower doses of air pollution can harm our eyes.

Studies have long found that air pollution is clearly harmful to health – especially the lungs (such as asthma) and cardiovascular systems (such as heart attacks and strokes). However, research on how dirty weather affects our eyes is only just beginning to emerge. “The eye is definitely an organ that is being neglected,” said Lena Mo, an epidemiologist at the University of Buffalo.

Our eyes are particularly vulnerable to dirty air, said Paul Foster, an eye epidemiologist at University College London. First, they are directly exposed to air pollution, which can lead to dry eye disease (when you don’t have enough high-quality tears to keep your eyes lubricated).

Second, the retina, the light-sensitive layer at the back of the eye, contains many blood vessels, making it very sensitive to pollution. “Anything that gets into the bloodstream will spread in very high concentrations to the back of the eye,” Foster said.

One of the major vision disorders that studies have linked to polluted air is glaucoma, a neurodegenerative disease in which the optic nerve located at the back of the eye is damaged. Research shows that high exposure to fine particles found in pollution — larger particles, called PM10, and finer particles, PM2.5, which come from sources including cars, trucks, power plants, residential heaters and wildfires — significantly increases the risk of developing this particular disease.

In one large study, doubling the average monthly concentration of PM2.5 in the air increased the risk of glaucoma by 66%.

The annual average PM2.5 level in the United States is about 10.3 micrograms/m3, which is low by global standards, but twice what World Health Organization guidelines say is acceptable. (About 97% of US cities did not meet WHO standards in 2021.) Many cities in Asia in particular are struggling with levels much higher than this. In 2021, New Delhi recorded an annual average PM2.5 concentration of 85 µg/m3.

However, even levels much lower than that can lead to vision problems, including glaucoma.

A French study published in September showed that exposure to PM2.5 at concentrations lower than the European Union’s recommendation of 25 micrograms/m3 may lead to rapid thinning of the nerves that transmit visual signals from the retina to the brain, a major indicator of glaucoma. .

According to Cécile Delcour, an epidemiologist at the National Institute of Health and Medical Research in France and lead author of the study, these results confirm that when it comes to healthy vision, there are actually no safe levels of air pollution.

Cataracts are also made worse by dirty air. A large British study by Foster and his colleagues found that people who live in areas with the highest levels of PM2.5 pollution have a 14 percent greater risk of needing surgery for cataracts — a disorder that causes the eye’s natural lens to become blurry, making objects appear larger. Clarity. Blurry and stripped of colour. Worryingly, the areas with the highest levels of pollution in that particular study were at lower levels than those in some US cities, such as Chicago and Los Angeles.

Under China’s often polluted skies, researchers have found that fine particle pollution may be responsible for nearly a quarter of all age-related cataract cases in the country.

China is also suffering from an epidemic of nearsightedness, also known as nearsightedness, and polluted air may be partly to blame, experts said. While up to 91% of Chinese high school students are nearsighted, this figure is only 13% in much less polluted Norway. Of course, other lifestyle factors, including screen use and outdoor time, may play a role here as well, as well as genetic differences.

A study in Taiwan found that the more PM2.5 and nitrogen oxides (of which NO2 is one type) are present in the air, the higher the risk of myopia: For children who live in places with particularly high levels of NOx, the risk of myopia is higher. The risk of developing myopia is more than doubled compared to children living in the cleanest areas.

On the plus side, green spaces that reduce pollution in a neighborhood were associated with a lower risk of myopia among children. It is recognized that this effect can be partly explained by the fact that parks keep children away from screens, which constitute an important risk factor for myopia.

While research on air pollution and vision in humans derives from observing health trends in groups — it would be unethical to subject people to pollutants and see what happens — studies in laboratory animals suggest that these effects are not just a coincidence. For example, when scientists made hamsters inhale high doses of PM2.5 twice a day, the animals became myopic after three weeks.

Once these small particles of pollution enter the lungs, they are “absorbed relatively quickly into the bloodstream, and that’s where these tiny particles start to have a more profound effect” on the animals, Foster said, and most importantly, they cause inflammation.

Laboratory experiments on human retinal cells in 2023 found that when these cells are exposed to particles, inflammation rises, which in turn is linked to vision disorders such as glaucoma.

Animal studies also show that exposure to polluted air can damage DNA in the retina and cause premature death of nerve cells in the back of the eye.

Mo said one possible way to counter the harmful effects of dirty air on eyes is to wear sunglasses, use lubricating eye drops, wash hands frequently, and avoid rubbing your eyes on days when air pollution levels are high, so as not to exacerbate any irritation. Amy Milne, an epidemiologist at the University of Buffalo, suggests eating a diet rich in antioxidants (think plenty of fruits and vegetables).

The good news is that compared to smoking or spending too much time in front of screens, air pollution has less impact on the eyes, Mo said. Bad news? “You can protect yourself from screen time; you can change your lifestyle, (but) air pollution is there, and you can’t avoid it.”

That’s why many experts believe the best way to protect vision from dirty air is to stop burning fossil fuels. “If we clean up the environment, there will be a benefit to the individual as well as to future generations,” Foster said.

Until then, fog glasses may not be a bad idea.

Sign up for the Well+Being newsletter, your source of expert advice and simple tips to help you live well every day

You may also like...

Leave a Reply

Your email address will not be published. Required fields are marked *