Polluted air quality increases risk of kidney disease

Researchers at the Clinical Epidemiology Center of St. Louis, Missouri recently discovered that air pollution increases the risk for chronic kidney disease (CKD), which can ultimately develop into end stage renal disease (ESRD).

Currently 30 million American adults suffer from CKD. A person with CKD has malfunctioning kidneys, meaning that fluid, electrolytes and other wastes gradually build up in their body because their kidneys cannot properly filter blood at a level needed for day-to-day life.

After 10 to 20 years, the kidneys slowly stop working, which is a sign that a person with CKD now has ESRD. As of 2013, more than 660,000 Americans were being treated for ESRD.

As far as scientists know, diabetes and hypertension (commonly known as high blood pressure) are two of the main leading causes of CKD. Previous studies have also demonstrated the correlation between air pollution and increased risk for cardiovascular disease; however, researchers have not yet started looking into the effects of air pollution on CKD.

This new study published in the Journal of the American Society of Nephrology sought to investigate this question.

The research team was led by Benjamin Bowe, a medical statistician, and Ziyad Al-Aly, the study’s senior author and an assistant professor of medicine at Washington University in St.Louis.

They worked off the results of prior experiments which showed that exposing mice to fine exhaust particles from gasoline engines led to oxidative stress, inflammation, DNA damage and changes in the way blood flows in the kidneys.

All of these factors eventually lead to acute renal failure, a phenomenon where the kidneys can no longer filter waste from the blood.

Epidemiologists recruited 2,482,737 test subjects, most of whom were white males. The participants lived in one of four counties: County one had a concentration of fine exhaust particles from 5.0 and 9.1 mg/m3, county two from 9.2 to 11.0 mg/m3, county three from 11.1 to 12.6 mg/m3 and county four from 12.7 to 22.1 mg/m3.

The study revealed that participants living in county four who were exposed to the highest concentration of particles were not only more likely to be African American but also more likely to suffer from hypertension, diabetes mellitus, cardiovascular disease and a higher estimated glomerular filtration rate (eGFR).

The term eGFR is a calculation based on the results of a test that measures the levels of creatinine in the blood. It also factors into account other variables such as age, sex and race. A high eGFR is indicative of kidney malfunction.

Bowe and Al-Aly subsequently found that the incidence of a high eGFR, CKD and ESRD increased across the counties, with county four having the highest incidence of CKD and county one the lowest.

The team tracked the test subjects’ progress over eight and a half years. They found that the incidence of eGFR increased for most of them, especially for those participants who had two high eGFR measurements within 90-day increments of each other.

The team also used data from NASA satellite sensors to determine the levels of concentrations of fine exhaust particles.

“The beauty of using both EPA and NASA data is that the agencies used two distinct techniques for collecting data, yet the results were similar,” Al-Aly said during a press release.

Al-Aly went on to describe their results.

“This constellation of findings suggests that chronic exposure to air pollution is a significant risk factor for the development and progression of kidney disease,” he said.

Through these experiments, the researchers found that residents inhabiting regions in the Northeast, Midwest and the South, as well as Southern California, were most at risk for developing CKD. However, high levels of air pollution might not be the sole concern for these residents.

“Even at relatively low levels, there was a relationship between particulate matter concentrations below the EPA thresholds and kidney disease,” Al-Aly said.

In the future Bowe and Al-Aly hope to conduct further experiments to assess the global burden of kidney disease caused by breathing in dirty air.

“The higher the levels of air pollution, the worse it is for the kidneys,” Al-Aly said. “However, no level is completely safe.”