Reference: Perfluorinated Chemicals as Emerging Environmental Threats to Kidney Health.
Chemicals and Kidneys, aka Chemical Filters Extraordinaire
How do chemical pollutants affect the health of our kidneys? That’s a question that’s hard to answer with any one research study. The kidneys are complicated organs, involved in waste removal, fluid balance, and blood pressure regulation. How do we measure effect on this complex organ system and determine what’s impactful? Do we look at the prevalence and severity of kidney disease in groups of people with known exposures to the chemicals? Do we have to wait until exposure manifests as disease in the whole organism, or can we get a sneak peek by looking directly at kidney tissue? Can we see changes in the structure of the tissue, and if so, do these changes necessarily predict impacts on functioning? Do functional changes at the tissue level always lead to a measurable effect on the health of the organism? What if we even drill down to the cellular and sub-cellular levels?
These questions are too diverse for any one researcher, or even any one field. Researchers chip away at the questions within their respective specialties: epidemiologists look at population-level clinical outcomes like mortality related to kidney diseases and changes in kidney function. Pathologists and histologists look at changes at the tissue level, while cellular and molecular biologists research outcomes in the pathways of kidney cells. How can these diverse fields of knowledge be aggregated into a more comprehensive understanding of chemical impacts on kidney health?
Researchers recently sought to accomplish this by conducting a systematic review of published literature from the fields of epidemiology, pathology, histology, and cellular and molecular biology. They were specifically interested in a group of chemical compounds knows as PFASs—per- and polyfluoroalkyl substances.
What are PFASs?
Per- and polyfluoroalkyl substances, or PFASs, are globally ubiquitous pollutants. Used in consumer products for their stain- and grease-repelling properties, they make their way out of products and into soil, air, and water. When we humans ingest contaminated food and water or inhale contaminated air, we can be exposed to PFASs. PFASs are so widespread that detectable levels are found in most people. Despite this ubiquitous exposure, the human health impacts of PFASs are only recently being studied. Initial findings suggest links to cancer and disruptions of the endocrine, metabolic, and immune pathways. To further our understanding of how PFASs affect human health, researchers at Duke University decided to summarize the accumulated knowledge assessing the impact of PFASs on kidney health.
After conducting a comprehensive search, the researchers, led by John Stanifer, identified 74 studies that investigated PFAS exposure and kidney-related health. 21 of those studies were at the population level (epidemiology), 13 looked at how kidneys metabolized, distributed, or eliminated PFASs from the system (pharmacokinetics), and 40 researched how PFAS exposure affected clinical, tissue, and cellular outcomes.
What did the researchers learn?
Collectively, results indicate that PFASs do have a negative impact on kidney health, though we have more to learn. Epidemiologic studies consistently demonstrate an association between PFAS exposure and increased kidney cancers and reduced kidney function. PFAS exposure in laboratory settings leads to measurable impacts on the cellular and tissue pathways known to be linked to kidney disease.
Most of the epidemiologic studies are limited in that they are cross-sectional, meaning that the concentration of PFASs was measured in the study participant at the same time as kidney health was assessed. We cannot infer that one condition caused the other; we only know that they are associated. However, factors like the replication of results and dose-response (i.e. people with higher concentrations of PFASs show greater incidence of kidney health issues) do give more credence to these cross-sectional findings.
The chemical industry has begun phasing out many PFASs from production in response to human health concerns. However, they are being replaced by alternative chemicals which seem to already be playing out the same story: they are being detected in soil, air, and water, and their impact on human health has not been adequately studied.
This publication and the 74 independent studies it reviewed raise the alarm that widespread exposure to PFASs and their alternatives appear to be impacting human kidney health. More research is needed to refine these findings and tease out how PFAS exposure interacts with genetic, biologic, lifestyle, and other environmental risk factors to ultimately impact kidney health.