Polystyrene microplastics alter gut bacteria and metabolism

A study partly funded by NIEHS found that exposure to polystyrene microplastics significantly altered gut bacteria growth and metabolism, highlighting potential risks to human health. Microplastics are widespread in the environment, and their presence in food and water has raised public health concerns. The researchers aimed to investigate how microplastics affect gut bacteria composition and function.

First, the team exposed three bacterial strains commonly found in the human gut — Escherichia coli, Nissle 1917, and Lactobacillus rhamnosus — to varying concentrations of polystyrene microplastics in the lab. Polystyrene is a type of plastic used widely to make food containers, consumer goods, electronics, and more. The researchers found that higher exposure to this chemical was associated with decreased bacterial growth. Further analysis revealed that the polystyrene disrupted key metabolic pathways, such as sulfur metabolism and amino sugar processing, which are crucial for various cellular processes.

The researchers then collected fecal samples from mice and co-incubated the samples with polystyrene microplastic for 24 hours. DNA analysis revealed that the exposure dysregulated bacteria important for maintaining gut health, such as Lactobacillales and Erysipelotrichales. The exposure also disrupted pathways crucial for energy production and altered how bacteria metabolize the amino acid tryptophan, which helps regulate appetite, sleep, mood, and pain.

According to the authors, these findings suggest that polystyrene microplastics exposure disrupts the gut microbiome by altering bacterial growth and metabolism. Future research should expand on these findings to better understand the long-term health risks associated with microplastics exposure. (MV)

Citation: Chi J, Patterson JS, Jin Y, Kim KJ, Lalime N, Hawley D, Lewis F, Li L, Wang X, Campen MJ, Cui JY, Gu H. 2025. Metabolic reprogramming in gut microbiota exposed to polystyrene microplastics. Biomedicines 13(2):446.

Wildfire smoke can harm lung immune function

Exposure to wildfire smoke can damage cells in the lungs that defend against infection and injury, found NIEHS-funded researchers. This is the first study to examine particulate matter in smoke collected during a wildfire event to better understand how that exposure affects lung macrophages, which are the cells responsible for clearing bacteria, viruses, and other harmful debris from the lungs.

Scientists collected wildfire particulate matter (WFPM) in the New Jersey/New York metropolitan area during the June 2023 Canadian wildfire event, which caused several days of poor air quality. Using computer models, they estimated how much of these particles people likely inhaled and deposited into the lungs.

The researchers then exposed lung macrophages to WFPM particles, either less than 0.1 micrometer or between 0.1 and 2.5 micrometers for 24 hours. After exposure, they tested for cell damage, stress levels, and how well the lung macrophages could clear harmful substances.

Exposure to the larger particles increased oxidative stress in macrophages by approximately 15%, a level that can damage the cells. Both small and large particles blocked receptors that play a crucial role in defending the lung against pathogens and made the macrophages about 50% less effective at capturing and clearing harmful substances. Both particle sizes also reduced levels of ATP, a molecule that stores and transports energy within cells, preventing macrophages from working properly and reducing lung cell survival.

According to the authors, these findings suggest that wildfire smoke exposure weakens the lungs’ immune defenses, potentially increasing the risk of respiratory infections. More research is needed to better understand how wildfire smoke affects overall lung health and immunity, they added. (MV)

Citation: Bazina L, Deloid G, Fritzky L, Lizonova D, Vaze N, Demokritou P. 2025. Impact of Canadian wildfire-emitted particulate matter on THP-1 lung macrophage health and function. Environ Sci Technol 59(8):3869-83.

Combustion byproducts found in soil after East Palestine train derailment

An NIEHS-funded study found higher levels of dioxins, furans, and environmentally persistent free radicals (EPFRs) in the soil at the East Palestine, Ohio, train derailment site after the accident compared to nearby soil before the accident. The study suggests that elevated levels of these contaminants remain at the derailment site and may require further monitoring. The February 2023 train derailment released chemicals that were intentionally burned off and spilled into the soil.

EPFRs are contaminants formed during combustion when chemicals interact with certain metals, such as those in train cars or in soil. Dioxins and furans are also formed during the burning of chemicals like those spilled during the train derailment.

The researchers hypothesized that EPFRs, dioxins, and furans were created simultaneously during combustion and that soil near the derailment site would have higher levels of the pollutants compared with soil farther away. The scientists collected soil samples around East Palestine and within a two-mile radius of the derailment site. They tested the samples for concentrations of EPFRs, dioxins, and furans and analyzed the relationship between their levels. For comparison, the scientists also tested soil samples collected before the accident from a nearby site.

The researchers found that soil concentrations of EFPRs were 10 times higher at the derailment site, and dioxin and furan levels were also higher near the site. In addition, EPFR concentrations were correlated to dioxin and furan levels.

According to the authors, these findings corroborate previous research that reported EPFRs may share a source with dioxins and furans. This is the first study to show a link between EPFRs and dioxin and furan concentrations in soil, the authors added. (MZ)

Citation: Lard ML, Eichler SE, Gao P, Singh K, Ortiz JD, Cook RL, Lomnicki S, Cormier SA, Richmond-Bryant J. 2025. Soil contamination by environmentally persistent free radicals and dioxins following train derailment in East Palestine, OH. Environ Sci Process Impacts 27(3):729-40.

PFAS exposure may increase risk of childhood leukemia

Childhood exposure to PFAS mixtures through house dust may increase the risk of developing childhood acute lymphoblastic leukemia (ALL), according to researchers funded by NIEHS. ALL, a cancer of blood and bone marrow, is the most common type of cancer in children.

PFAS are a class of long-lasting contaminants that may be toxic to the immune system and are linked to certain cancers in adults. House dust is a source of PFAS exposure in young children who crawl and spend most of their time indoors. Although there is some evidence that PFAS exposure may be linked to childhood cancers, most research has not focused on the effects of PFAS on children.

The researchers collected vacuum bags from Californian households with children diagnosed with ALL, as well as from control households, and analyzed the vacuumed dust for levels of eight types of PFAS. The team found that higher levels of the PFAS mixture in house dust were linked to an overall higher risk of childhood ALL. EtFOSAA, a type of PFAS used in various consumer products, such as carpets and packaging paper, was most strongly related to increased risk of childhood ALL compared with other PFAS found in the dust samples.

According to the authors, this study is among the first to identify a link between childhood PFAS exposure from house dust and an elevated risk of childhood ALL. In addition, the study was the first to report a link between EtFOSAA and an increased risk of childhood ALL. (MZ)

Citation: Metayer C, Morimoto LM, Vieira VM, Godri Pollitt KJ, Bartell SM, Wong L, Young TM. 2025. Exposure to per- and polyfluoroalkyl substances in residential settled dust and risk of childhood acute lymphoblastic leukemia. Int J Cancer; online ahead of print Feb 14. doi; 10.1002/ijc.35370