Studies have already confirmed the link between air pollution and respiratory health. Exposure to polluted air increases a person’s risk of developing respiratory problems like asthma and organ inflammation, along with other life-threatening conditions. However, data from a recent study suggests that air pollution also increases the risk of chronic kidney disease, a condition where the kidney becomes damaged or unable to filter blood properly.

The study, which was published in PLOS ONE, involved researchers from the University of Michigan.

Dr. Jennifer Bragg-Gresham, the study’s lead author, said that like smoking, air pollution has toxins that may directly affect the kidneys.

Dr. Bragg-Gresham, who is also an epidemiologist at Michigan Medicine, added that since the “[kidneys] have a large volume of blood flowing through them,” they are the first organs to suffer if anything harms the circulatory system. Individuals with diabetes, heart disease, high blood pressure, or obesity have a higher chance of developing chronic kidney disease. This highlights the need for high-risk patients who live in densely populated or polluted areas to take the necessary precautions. (Related: Exposure to air pollution found to increase risk of chronic kidney disease.)

Why is air pollution bad for you?

Air pollution comprises many harmful substances, but few are as dangerous as fine particulate matter, which is made from various microscopic particles. Fine particulate matter, better known as PM2.5, are fine inhalable particles that have a diameter of about 2.5 micrometers or smaller. By comparison, a single strand of human hair has a diameter of about 70 micrometers, making it 30 times larger than PM2.5.

The particles are almost weightless and can stay in the air longer, which means that people can involuntarily inhale them. If a person is exposed to PM2.5 for extended periods, it can cause health problems.

Researchers looked at data from Medicare claims, as well as air-quality data from the Centers for Disease Control and Prevention. They discovered a link between chronic kidney disease rates and PM2.5 concentration. Dr. Rajiv Saran, a Michigan Medicine nephrologist and the director of the United States Renal Data System Coordinating Center at UM, commented that unlike less polluted areas, heavily polluted areas have higher rates of chronic kidney disease.