FOREVER CHEMICALS
PFAS can suppress white blood cell’s ability to destroy invaders
In a new study, researchers found that the PFAS chemical GenX suppresses the neutrophil respiratory burst – the method white blood cells known as neutrophils use to kill invading pathogens. The study is an important first step in understanding how both legacy and emerging PFAS chemicals might affect the body’s innate immune system.
PFAS are a class of per- and polyfluoroalkyl chemicals used to make consumer and industrial products more resistant to water, stains and grease. According to the U.S. Environmental Protection Agency, there are more than 12,000 known PFAS, which also include fluoroethers such as GenX.
“It’s pretty well-established that PFAS are toxic to the adaptive immune system, but there hasn’t been as much research done on their effects on the innate immune system,” says Drake Phelps, former Ph.D, student at North Carolina State University and first author of the study.
The human immune system has two branches: adaptive and innate. The adaptive branch contains T cells and B cells that “remember” pathogens the body has encountered, but it is slow to mount a defense, acting days – sometimes weeks – after it detects a pathogen.
The innate immune system serves as the body’s first responders, and contains white blood cells that can be dispatched to the site of an invasion within hours. These white blood cells include neutrophils, which can dump reactive oxygen species – think tiny amounts of bleach or hydrogen peroxide that neutrophils manufacture inside their cells – directly onto pathogens, killing them. That process is called the respiratory burst.
Drake and the research team looked at the effect of nine environmentally relevant legacy and emerging PFAS on neutrophils from zebrafish embryos, neutrophil-like cells (cells that can be chemically treated to behave like neutrophils), and human neutrophil cells cultured from donor blood.
Emerging PFAS are chemicals, like GenX, developed to replace older, legacy PFAS that had proven toxic. All of the PFAS included in this study were detected in both the Cape Fear River and the blood serum of residents whose drinking water came from the Cape Fear River.
The embryos and cells were exposed to 80 micromolar solutions of each chemical:
perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid potassium salt (PFOS-K), perfluorononanoic acid (PFNA), perfluorohexanoic acid (PFHxA), perfluorohexane sulfonic acid (PFHxS), perfluorobutane sulfonic acid (PFBS), ammonium perfluoro(2-methyl-3-oxahexanoate) (GenX), 7H-perfluoro-4-methyl-3,6-dioxa-octane sulfonic acid (Nafion byproduct 2), and perfluoromethoxyacetic acid sodium salt (PFMOAA-Na).
Of the nine PFAS tested, only GenX suppressed the neutrophil respiratory burst in embryonic zebrafish, neutrophil-like cells, and human neutrophils. PFHxA also suppressed the respiratory burst, but only in embryonic zebrafish and neutrophil-like cells.
The researchers caution that while the results of this preliminary study are interesting, they raise more questions than they answer.
“The longest chemical exposure in our study was four days, so obviously we can’t compare that to real human exposure of four decades,” says Jeff Yoder, professor of comparative immunology at NC State and corresponding author of the work. “We looked at a high dose of single PFAS over a short period, whereas people in the Cape Fear River basin were exposed to a mixture of PFAS – a low dose over a long period.
“So while we can say that we see a toxic effect from a high dose in the cell lines, we can’t yet say what effects long-term exposure may ultimately have on the immune system. This paper isn’t the end of the road – it’s the first step. Hopefully our work may help prioritize further study of these two chemicals.”
The study appears in the Journal of Immunotoxicology and was supported by the National Institute of Environmental Health Sciences (NIEHS), the North Carolina State University Center for Environmental and Health Effects of PFAS, and the North Carolina State University Center for Human Health and the Environment (CHHE). Jamie DeWitt, professor of pharmacology and toxicology at East Carolina University, is co-author.
-peake-
Note to editors: An abstract follows.
“Legacy and Emerging Per- and Polyfluoroalkyl Substances Suppress the Neutrophil Respiratory Burst”
DOI: 10.1080/1547691X.2023.2176953
Authors: Drake W. Phelps, Anika I. Palekar, Haleigh E. Conley, Giuliano Ferrero, Jacob H. Driggers, Keith E. Linder, Seth W. Kullman, David M. Reif, M. Katie Sheats, Jeffrey A. Yoder, North Carolina State University; Jamie DeWitt, East Carolina University
Published: Feb. 15, 2023 in Journal of Immunotoxicology
Abstract:
Per- and polyfluoroalkyl substances (PFASs) are used in a multitude of processes and products, including non-stick coatings, food wrappers, and fire-fighting foams. These chemicals are environmentally-persistent, ubiquitous, and can be detected in the serum of 98% of Americans. Despite evidence that PFASs alter adaptive immunity, few studies have investigated their effects on innate immunity. The report here presents results of studies that investigated the impact of nine environmentally-relevant PFASs [e.g., perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid potassium salt (PFOS-K), perfluorononanoic acid (PFNA), perfluorohexanoic acid (PFHxA), perfluorohexane sulfonic acid (PFHxS), perfluorobutane sulfonic acid (PFBS), ammonium perfluoro(2-methyl-3-oxahexanoate) (GenX), 7H-perfluoro-4-methyl-3,6-dioxa-octane sulfonic acid (Nafion byproduct 2), and perfluoromethoxyacetic acid sodium salt (PFMOAA-Na)] on one component of the innate immune response, the neutrophil respiratory burst. The respiratory burst is a key innate immune process by which microbicidal reactive oxygen species (ROS) are rapidly induced by neutrophils in response to pathogens; defects in the respiratory burst can increase susceptibility to infection. The study here utilized larval zebrafish, a human neutrophil-like cell line, and primary human neutrophils to ascertain whether PFAS exposure inhibits ROS production in the respiratory burst. It was observed that exposure to PFHxA and GenX suppresses the respiratory burst in zebrafish larvae and a human neutrophil-like cell line. GenX also suppressed the respiratory burst in primary human neutrophils. This report is the first to demonstrate that these PFASs suppress neutrophil function and supports the utility of employing zebrafish larvae and a human cell line as screening tools to identify chemicals that may suppress human immune function.
JOURNAL
Journal of Immunotoxicology
METHOD OF RESEARCH
Experimental study
SUBJECT OF RESEARCH
Cells
ARTICLE TITLE
Legacy and Emerging Per- and Polyfluoroalkyl Substances Suppress the Neutrophil Respiratory Burst”
ARTICLE PUBLICATION DATE
15-Feb-2023
COI STATEMENT
DWP was paid a one-time fee by the Center for Environmental Health (Oakland, CA, USA) for serving as a scientific advisor (May 2019 to August 2022) to aid in writing a petition under the Toxic Substances Control Act to the United States Environmental Protection Agency, regarding testing of certain PFASs. JCD serves/has served as a plaintiff’s expert witness for several court cases involving PFAS manufacturers. All other authors declare no competing interests relevant to the content of this article.
Study: microbes play a key role in
unleashing 'forever chemicals' from
recycled-waste fertilizer
Drexel researchers show path of PFAs from biosolid fertilizer
Peer-Reviewed Publication“Forever chemicals” are everywhere — water, soil, crops, animals, the blood of 97% of Americans — researchers from Drexel University’s College of Engineering are trying to figure out how they got there. Their recent findings suggest that the microbes that help break down biodegradable materials and other waste are likely complicit in the release of the notorious per- and polyfluoroalkyl substances (PFAS) into the environment.
In a paper published in the Royal Society of Chemistry journal Environmental Science Processes & Impacts, the group showed how PFAS —chemicals that had been widely used in water, heat and stain-resistant products and have been linked to serious health problems — can leach out of fertilizer made from recycled waste with the help of microbial decomposition. The finding could help to explain how PFAS accumulates in the soil, crops and groundwater in farmland across the country.
“Because it is not currently possible to eliminate PFAS from the environment, it’s important to understand everything we can about how it is able to persist and accumulate so broadly in the natural world,” said co-author Asa Lewis, PhD, who led the research as a doctoral student at Drexel along with environmental engineers from Temple University. “Our work shows how microbial weathering fits into the PFAS dissemination pathway from biosolids.”
According to the Environmental Protection Agency, about half of all sewage waste in the U.S. – about 4.5 million metric tons -- is treated and converted to a sludge, called biosolid waste. About half of that goes through further treatment to remove biological and chemical contaminants and is converted into a fertilizer product. For the last 50 years, this fertilizer has been used throughout the country on farmland, residential gardens and landscaping.
But research in the last year raised concerns about this widespread use when it revealed that PFAS can persist in biosolid fertilizer, despite the treatment process.
“We know that microbes exist in biosolid sludge even after the stabilization treatment process and given the role they play in the decomposition of organic compounds, such as fats, protein, and polysaccharide residuals in the biosolids, we wanted to examine how microbial weathering of these organic compounds can impact PFAS leaching potential from biosolids over time because it PFAS compounds are thought to stick to these compounds,” said Christopher Sales, PhD, an associate professor in the College of Engineering and a co-author of the study.
To do it, the team collected biosolid samples that had undergone one of three types of treatment — aerobic digestion, anaerobic digestion or composting — at wastewater recycling and reuse facilities. The content of each sample was tested to determine the initial level of organic matter, proteins and lipids and PFAS concentration in these different types of biosolids. These samples were then placed in an environmentally controlled chamber for three months to look for indicators of microbial activity, especially degradation of organics, lipids and proteins, and sought to see how this microbial activity affected how much PFAS would partition from the biosolids into water.
The researchers found that the samples with the highest level of microbial activity also demonstrated the highest level of PFAS partitioning — an indicator that this biosolid sludge would be more susceptible to PFAS leaching.
The results demonstrated this increase in PFAS partitioning over the three months, especially in the first 10 days of the experiment, is likely due to the microbes breaking down proteins and lipids in the biosolid, which allows the PFAS to spread, or partition, as water passes through.
“This work provides evidence that microbial weathering processes that lead to degradation of organic matter and biopolymers — as indicated by lipase activity, protease activity, and oxygen consumption rate, as well as changes in lipid, protein, and organic content — can impact PFAS partitioning and increase leaching potential in biosolids,” the authors wrote.
The team noted that the results likely implicate microbes in the process of PFAS leaching from biosolids after they are land-applied, but further research is needed to confirm how they are transported through the soils to surface waters, like rivers and lakes, groundwaters and how they bioaccumulate in crops and animals that might graze where biosolids are applied. In addition, the rate of biosolid weathering in nature might be much different than their lab study considering the role that rainfall, solar irradiation, and physical disturbances impact soil weathering would play outdoors.
The team contends that in order for agencies like the EPA to provide accurate guidance on PFAS risk and acceptable levels of contamination, understanding the path of “forever chemicals” is critical information.
“This research provides evidence that PFAS can leach from biosolids across different stabilization methods in wastewater treatment,” Lewis said. “And it provides more support that regulation or advanced treatment in wastewater treatment plants is needed to reduce impacts to the environment.”
JOURNAL
Environmental Science Processes & Impacts
METHOD OF RESEARCH
Experimental study
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Influence of microbial weathering on the partitioning of per- and polyfluoroalkyl substances (PFAS) in biosolids
No comments:
Post a Comment