Long-Term PM2.5 Exposure May Damage Kidney Function, Finds Study

Long-term exposure to high levels of fine particulate matter (PM2.5) reduces the filtration efficiency of human kidneys. A study published in the journal Kidney International Reports tracked over 12,000 participants for six to 10 years. The researchers observed a consistent decline in kidney function linked directly to air pollution.

The decline remained evident even when researchers controlled for other risk factors such as diabetes and hypertension. This confirms that air pollution independently damages the kidneys, rather than solely through metabolic diseases.

"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." Dr V Mohan, chairperson of Dr Mohan’s Diabetes Specialties Centre in Chennai, said this in remarks reported by Indian Express.

"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)." Mohan said.

Chennai Vs Delhi

The study drew participants from Delhi and Chennai, two cities with vastly different ambient air pollution levels. Baseline PM2.5 levels stood at 118 μg/m3 in Delhi and 33 μg/m3 in Chennai. During subsequent visits, these levels rose to 123 μg/m3 and 130 μg/m3 in Delhi, while Chennai recorded 37 μg/m3 and 30 μg/m3.

Doctors measured the estimated glomerular filtration rates (eGFR)—used to check kidney health—and found it to be 112 mL/min/1.73 m2 for Chennai residents and 106.4 for Delhi residents. Although both values are normal, Delhi residents began with lower renal reserves.

The decline was also sharper in the national capital. Every 5 μg/m3 increase in annual average PM2.5 levels led to a kidney function decline of 0.42 in Delhi residents compared to 0.32 in Chennai residents.

"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." Dr Dorairaj Prabhakaran, executive director of the Centre for Chronic Disease Control told Indian Express.

Mechanisms And National Impact

India has 143 million people living with chronic kidney disease. Most of them reside in areas with some of the highest PM2.5 exposures in the world. Controlling diabetes, hypertension and obesity is as important as addressing this environmental factor to reduce chronic kidney disease rates across the country.

Medical experts point to several pathways through which PM2.5 damages the kidneys. These include chronic systemic inflammation, oxidative stress causing cell damage, dysfunction of the blood vessel lining, damage to the tiny blood vessels and small particles entering the blood circulation directly to reach the kidneys.

"These may be the possible ways in which the kidney is being damaged by air pollution." Mohan said.

"While we know of the impact of high pollution levels on the respiratory system, this adds to the evidence on the impact of the particulate matter on other organs as well. This provides further stimulus for policies to address air pollution." Mohan added.

Policy and Personal Action

Curbing air pollution requires both immediate personal protection and long-term policy interventions. Prabhakaran urges residents in highly polluted areas like Delhi to take precautions.

"In the meantime, people can protect themselves by donning N-95 masks when they go for their morning walks. Air purifiers are also a good idea. But, of course, overall policy measures to address pollution levels are needed." Prabhakaran said.

While short-term measures help, Mohan emphasizes that systemic cleanup is entirely achievable through public and policy action.

"It is not impossible. A couple of decades back, Los Angeles was probably as polluted as Delhi but they identified the problem areas and worked on it. People were involved and now the LA skies are clear. Take the example of Indore, if they are able to maintain a clean city year after year, action can be taken through similar mechanisms to curb pollution as well." Mohan added.