Long-term exposure to air pollution may significantly increase the risk of serious kidney diseases, according to new research analysing hospital admissions in Brazil’s largest city.
The study, published in the journal Scientific Reports, examined the relationship between PM2.5 and kidney disease hospitalisations in São Paulo over a 10-year period. Researchers found higher pollution levels were linked to increased rates of acute kidney injury, chronic kidney disease and glomerular diseases, which affect the kidneys’ filtering system.
PM2.5 particles are small enough to enter the bloodstream, scientists have long linked them to heart and respiratory illnesses. The new findings suggest they may also play a major role in damaging kidney health.
Researchers found that even relatively low pollution levels were associated with increased hospital admissions. The study noted that exposure to PM2.5 concentrations of 15 μg/m³ – the maximum daily level recommended by the World Health Organization – was enough to raise the risk of some kidney conditions.
The risks were not spread evenly across the population. Younger people appeared particularly sensitive to short-term pollution exposure, while older adults faced greater risks from long-term cumulative exposure. Men and younger to middle-aged adults were among the groups most affected.
One of the strongest findings involved glomerular disease, especially membranous nephropathy, a condition in which the kidney’s filtering membranes become damaged. Young men exposed to high levels of PM2.5 over long periods had a risk of hospitalisation more than five times greater than other age and sex groups studied.
The researchers analysed hospital records and air pollution data across São Paulo, a city of more than 22 million people where vehicle traffic is a major source of pollution. They found consistent links between worsening air quality and rising hospital admissions for kidney-related illnesses.
Iara da Silva, the first author of the study said: ‘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 hospitalisations for kidney diseases, indicating the need to intensify policies to reduce air pollution.’
Maria de Fátima Andrade, a professor at IAG-USP, who co-ordinated the study said: ‘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.’
In a previous study, her group compared the response to kidney injury in two groups of mice: one exposed to air from São Paulo and another exposed to the same air that had been filtered.
She explained: ‘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.’
The full research can be read here.
Photo: Sérgio Souza
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