Besides, negative effects on cardiovascular health and life expectancy, increased exposure to air pollution may also harm your kidneys, researchers warn.

The study suggests that there really is no "safe" level for air pollution, as even the lowest levels of particulate matter in the air can do great harm to the kidneys and lead to chronic kidney disease (CKD), a decline in glomerular filtration rate (eGFR)-- the rate of blood flow through the kidneys as well as end stage renal disease (ESRD) -- the last stage of CKD."Even levels below the limit set by the EPA were harmful to the kidneys. This suggests that there is no safe level of air pollution," said Ziyad Al-Aly, Director at the VA Saint Louis Health Care System in Missouri, US. "Our findings demonstrate a significant association between exposure to PM2.5 and risk of incident CKD, eGFR decline, and ESRD," Al-Aly added.

When we breathe, tiny particles present in the dirty air pass through our lungs and enter our bloodstream to finally reach kidneys. Kidneys -- our body's main filters -- sift these particles out of the blood. However, excess exposure to these harmful pollutants reduces the efficacy of the process, Al-Aly explained.For the study, which will appear in the Journal of the American Society of Nephrology (JASN), the team examined information on 2,482,737 US veterans who were followed for a median of 8.5 years. Air pollution levels were also assessed using space-borne sensors from NASA satellites.The researchers found a linear relationship between air pollution levels and risk of experiencing kidney function decline and of developing kidney disease or kidney failure. Each year in the US, 44,793 new cases of chronic kidney disease and 2438 new cases of kidney failure are attributed to particulate matter air pollution exceeding the Environmental Protection Agency's recommended limit of 12 �g/m3, the researchers said.