Long-term exposure to fine air pollution may gradually weaken kidney function, according to research involving more than 12,000 adults.
Researchers followed participants for six to ten years and tracked their exposure to PM2.5. These particles measure 2.5 micrometres or less and can travel deep into the body.
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The study, published in Kidney International Reports, linked higher PM2.5 exposure with reduced kidney filtration. Importantly, the association remained after researchers accounted for diabetes, hypertension and other established risk factors.
“This is a part of an ongoing series of studies that looks at the impact of air pollution on different diseases. So far, we have shown an association with higher air pollution levels and increased risk of hypertension, diabetes and dyslipidemia (high levels of blood fats like cholesterol and triglycerides). Now, we have shown that it impacts kidney function as well. And, the association remained consistent even after controlling for other factors, meaning the impact of air pollution on kidneys is not through the increases in diabetes and hypertension, but independently as well,” said Dr V Mohan, one of the study’s authors.
Higher PM2.5 Exposure Linked to Faster Kidney Decline
The researchers compared adults who lived under sharply different pollution conditions. At baseline, average PM2.5 exposure measured 33 micrograms per cubic metre in the lower-exposure group. Meanwhile, the higher-exposure group recorded 118.
Later measurements reached 37 and 30 in the lower-exposure group. In comparison, the higher-exposure group recorded 123 and 130.
Researchers also measured estimated glomerular filtration rate, or eGFR. Doctors use this figure to assess how efficiently the kidneys filter waste from the blood.
The lower-exposure group recorded an average eGFR of 112 mL/min/1.73 m2. By contrast, the higher-exposure group recorded 106.4.
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Although both averages remained within the normal range, people facing heavier pollution started with lower kidney reserves.
Moreover, each five microgram increase in annual PM2.5 exposure reduced eGFR by 0.42 in the higher-exposure group. The same increase caused a decline of 0.32 in the lower-exposure group.
“The study clearly shows that an increase in PM2.5 exposure is linked with worsening kidney function. There could be as much as 4% decline in a year. We know that kidney function goes down with age, but if you start with lower reserves, the damage with age would be quicker,” said Dr Dorairaj Prabhakaran, another study author.
Experts Call for Stronger Pollution Controls
Doctors say PM2.5 may harm the kidneys through chronic inflammation, oxidative stress and damage to blood vessels. In addition, the particles can enter the bloodstream and travel directly to the kidneys.
“The findings show that long-term exposure to fine air pollution may gradually reduce kidney function even in younger adults who do not already have chronic kidney disease (CKD),” Dr Mohan said.
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Therefore, experts say governments must treat air pollution as more than a respiratory threat. It may also contribute to kidney disease, heart problems, diabetes and other long-term conditions.
People can reduce short-term exposure by wearing N95 masks outdoors and using air purifiers indoors. However, researchers stress that only broader environmental policies can deliver lasting protection.
