A study supported by FAPESP and published in the journal Scientific Reports showed a strong correlation between the concentration of particulate matter in the air of São Paulo, Brazil – primarily emitted by vehicle fuel combustion – and kidney disease.
The study estimated the risk of hospitalization for three kidney conditions based on the levels of this type of air pollution from 2011 to 2021. Men across different age groups were found to be at the highest risk of hospitalization.
Exposure to even low concentrations of this pollutant – considering the World Health Organization (WHO) limit of 15 micrograms per cubic meter (μg/m³) of fine particulate matter over 24 hours – is sufficient to increase men's risk of hospitalization for acute kidney injury, one of the conditions analyzed. In this case, the risk does not increase for women.
"Exposure of São Paulo residents to this material reached 65 μg/m³, more than four times the maximum tolerable level according to the WHO. However, even concentrations within the limit showed a link to hospitalizations for kidney diseases, indicating the need to intensify policies to reduce air pollution," says Iara da Silva, the first author of the study. Da Silva conducted the research as part of her doctoral studies at the Institute of Astronomy, Geophysics, and Atmospheric Sciences at the University of São Paulo (IAG-USP), and she is currently pursuing postdoctoral research at the Federal Technological University of Paraná (UTFPR).
The study is part of the project "Air Pollution Is the Driver of Premature Kidney Aging" , which is supported by FAPESP and the Netherlands Organization for Scientific Research (NWO). Lucia Andrade , a professor at the USP Medical School (FM-USP), is coordinating the project.
The study also received support from FAPESP through the project "São Paulo Metropolitan Area: An Integrated Approach to Climate Change and Air Quality" ( METROCLIMA MASP ), coordinated by Maria de Fátima Andrade , a professor at IAG-USP.
Increased risk
Fine particulate matter consists of solid or liquid particles smaller than 2.5 micrometers (μm) – one micrometer is equal to one-thousandth of a millimeter. The results indicate that exposure to this type of pollution increases the risk of hospitalization for chronic kidney disease by up to four times across different age groups and exposure levels.
Long-term exposure to the highest level of fine particulate matter found during the study period (65 μg/m³) significantly increased the risk of chronic kidney disease for individuals aged 19 to 50 and was up to 2.5 times higher for men aged 51 to 75.
Prolonged exposure to high concentrations increased the risk of hospitalization for acute kidney injury, another kidney-related condition, among men aged 19 to 50. The risk of glomerulopathies, which affect the structures responsible for filtering blood, was higher for men under 40, especially those exposed to concentrations ranging from 15 μg/m³ (the 24-hour exposure limit recommended by the WHO) to 65 μg/m³ (the highest value found in the study).
This level of exposure also increased the cumulative risk of hospitalization for membranous nephropathy, a form of glomerulopathy, regardless of age or sex.
"The hypothesis is that particulate matter can enter the bloodstream and deposit in kidney tissue, where it's recognized by the immune system as a foreign body, causing the body to produce a series of inflammatory mediators, as well as mediators of fibrosis and premature aging [senescence]," Andrade explains.
In a previous study , her group compared the response to acute kidney injury in two groups of mice: one exposed to air from São Paulo and another exposed to the same air that had passed through filters.
"In the animals, we observed that those exposed to the particulate matter had a more severe disease. There was a decrease in glomerular filtration, more inflammation in the kidneys, more necroptosis [cell death] pathways, and they also exhibited markers of senescence and fibrosis. In the long term, there's a higher chance that the condition will progress to chronic kidney disease," she states.
The researchers are concerned about the quality of life and healthcare costs associated with these preventable diseases, which would be less severe with lower pollution levels. In severe cases, patients require hemodialysis, a procedure that filters blood outside the body, and even kidney transplants. There is a long waiting list for these transplants.
In an upcoming study, the Brazilian and Dutch team will follow transplant patients and compare health outcomes across different levels of particulate matter exposure.
"There are public policies to reduce air pollution currently in place, but they haven't been sufficient. We really need a new development model that doesn't rely on burning fossil fuels, the primary cause of global warming," Silva concludes.
The study received support from FAPESP in the form of a doctoral scholarship for Caroline Fernanda Hei Wikuats at the IAG-USP, with an internship at the University of Amsterdam in the Netherlands.
About São Paulo Research Foundation (FAPESP)
The São Paulo Research Foundation (FAPESP) is a public institution with the mission of supporting scientific research in all fields of knowledge by awarding scholarships, fellowships and grants to investigators linked with higher education and research institutions in the State of São Paulo, Brazil. FAPESP is aware that the very best research can only be done by working with the best researchers internationally. Therefore, it has established partnerships with funding agencies, higher education, private companies, and research organizations in other countries known for the quality of their research and has been encouraging scientists funded by its grants to further develop their international collaboration. You can learn more about FAPESP at www.fapesp.br/en and visit FAPESP news agency at www.agencia.fapesp.br/en to keep updated with the latest scientific breakthroughs FAPESP helps achieve through its many programs, awards and research centers. You may also subscribe to FAPESP news agency at http://agencia.fapesp.br/subscribe.
