News

Fact/Fiction: Does air pollution make you blind?

Old news, truthfully retold. This week we investigate claims that living next to a busy road is linked to glaucoma

How it was told

With the health of the planet a main focus of the Extinction Rebellion movement and the Climate Strikes, it’s almost easy to forget that air pollution isn’t exactly good for the human body either.

Two studies last week delivered a stark reminder of the impact that the emissions we breathe in can have. One centred on how living next to busy roads can cause lung cancer but we’ll focus on another one this week, a University College London study that linked air pollution to glaucoma, the eye condition that can cause damage to sight and even blindness through damage to the optic nerve.

The Sun led the charge with the coverage, opting for the headline “EYES AND LOWS. Living near a busy road could put you at risk of going blind, experts warn”.

The Independent’s headline was a little more straightforward, they went for: “Air pollution linked to condition that causes blindness in major UK study”.

“Air pollution linked to blindness as scientists say particles may hinder blood vessels in eyes” was The Daily Telegraph’s effort, focusing on the science behind the study’s claims.

And, finally, Mail Online stuck to their tried-and-tested lengthy headline format in: “Air pollution ‘can trigger glaucoma’: Study finds chemicals in air narrow the blood vessels and raise the risk of the condition by 6%”.

We already know that air pollution is damaging, but does this latest claim stack up?

Facts. Checked

To be fair to all the news outlets, they do a decent job of reporting this study which, even by the researchers’ own admission, doesn’t have the answers.

However, that’s not to say that their findings are not important – but there is more work to be done to definitively answer the question.

The study, which was published in the Investigative Ophthalmology and Visual Science journal, was certainly large, analysing 111,370 UK Biobank participants between 2006 and 2010. The participants were asked if they had glaucoma before undergoing ocular testing as well as a laser scan of the retina to measure thickness of their eye’s macula (the central area of the retina).

This information was then linked to air pollution measures of their home addresses, with the academics finding that people in the most polluted quarter of areas were 18 per cent more likely to report glaucoma than the least polluted 25 per cent. As Professor Paul Foster put it: “We found a striking correlation between particulate matter exposure and glaucoma. Given that this was in the UK, which has relatively low particulate matter pollution on the global scale, glaucoma may be even more strongly impacted by air pollution elsewhere in the world.”

However, there are plenty of limitations to this study that mean a causal link is yet to be confirmed.

By Prof Foster’s own admission, the scientists were not able to test the air pollution inside people’s homes or workplaces as this is an observational study. Neither were they able to experiment by changing the levels of pollution, as The Open University’s Emeritus Professor of Applied Statistics Professor Kevin McConway points out in response, as this would be impossible and unethical.

And it is also tricky to compare other differences between high and low pollution areas that could explain increased glaucoma risk – although the study’s authors did attempt to account for age, sex and a measure of material deprivation, as well as a few other factors.

They also didn’t have any data on the actual pollution levels recorded over time in each area, which means that it isn’t possible to prove Prof Foster’s claim about other areas of the world.

As for the science, all outlets quoted the study’s first author Dr Sharon Chua and her explanation that “the constriction of blood vessels” may contribute to glaucoma or air pollution may “have a direct toxic effect damaging the nervous system”.

While the news outlets did portray the study cautiously, only The Independent quoted Prof McConway’s observations or any observations outside of the study to point out some of the study’s flaws.

Illustration: Miles Cole

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