ks

a kidney stone is a hard object that forms from minerals and other chemicals in the urine. According to work by three kidney health societies - the American Society of Nephrology, European Renal Association–European Dialysis and Transplant Association, and International Society of Nephrology, 850 million people have kidney diseases.

National Kidney foundation: Jinbo Chen and Minghui Liu, who are urologists at Xiangya Hospital, part of China's Central South University, explain that air pollutants such as small particulate matter with a diameter of 2.5 µm or less (PM2.5) and nitrogen dioxide (NO2) can increase the risk of kidney stone disease through several biological pathways.

For example, PM2.5 can penetrate deep into the lungs, cross into the bloodstream, and eventually reach the kidneys, where the particles trigger oxidative stress, Chen says. This process causes an imbalance between free radicals and antioxidants that can impair kidney function. "Specifically, it may disrupt proteins like Tamm-Horsfall protein that normally prevent crystal formation, leading to the growth of calcium oxalate stones, a common type of kidney stone," he says.

pollutants also activate the immune system, he says, causing chronic low-level inflammation. This persistent inflammation harms kidney tissues, making it easier for crystals to build up and form kidney stones.

Chen also says that air pollution harms blood vessels, including the tiny ones in the kidneys, which can reduce blood flow there and change urine's concentration and acidity. Such changes can make it harder for the kidneys to keep minerals balanced, indirectly increasing the chance of forming kidney stones.