Washington :  Outdoor air pollution has long been linked to major health conditions such as heart disease, stroke, cancer, asthma and chronic obstructive pulmonary disease.

Researchers evaluated the effects of air pollution and kidney disease on nearly 2.5 million people over a period of 8.5 years, beginning in 2004.

They compared data on kidney function to air-quality levels collected by the US Environmental Protection Agency (EPA) as well as NASA.

The findings suggest that 44,793 new cases of kidney disease and 2,438 cases of kidney failure may be attributed to levels of air pollution that exceed the EPAs threshold of 12 microgrammes per cubic metre of air, which is the highest level of air pollution considered safe for the public, researchers said.

“However, once we analysed the data, the link between air pollution and the development of kidney disease was clear,” said Al-Aly, senior author of the study published in the Journal of the American Society of Nephrology.

Fine particles can damage the kidneys in the same way they damage other organs such as the heart and lungs.

Airborne and invisible, microscopic pieces of dust, dirt, smoke, soot and liquid droplets often become destructive when they invade the bloodstream.

The kidneys filter the blood, and these harmful particles can disrupt normal kidney function.

The study found that even low levels of particulate matter may adversely affect the kidneys. And those adverse effects increase as pollution levels increase.

“However, no level is completely safe. Even at relatively low levels, there was a relationship between particulate matter concentrations below the EPA thresholds and kidney disease,” he said.