Circadian rhythms may influence how the body detoxifies food contaminants

The timing of meals may affect how well the liver breaks down food contaminants such as pesticides, according to researchers supported in part by NIEHS.

Food often contains contaminants such as pesticide residues and chemicals introduced through food processing, packaging, or cooking. These substances can interfere with the absorption of nutrients and contribute to a range of health problems. Because liver enzymes that metabolize food contaminants follow circadian clock rhythms, researchers hypothesized that the timing of meals could influence their toxic effects.

To explore this possibility, the researchers asked 45 adults to eat the same amount and type of fruit and vegetables within either a morning or evening three-hour window, while maintaining their normal diet, over a two-week period. The researchers measured 125 biomarkers of food contaminants in urine samples. The results showed that the timing of meals altered the urinary body burden (concentrations) and temporal patterns of numerous classes of chemicals, including pesticides, compounds from smoking, estrogen-mimicking compounds, volatile organics, parabens, phthalates, and flame retardants. Pesticides and volatile organics, in particular, were linked to molecular oxidative stress and tissue damage.

According to the researchers, the findings suggest that circadian rhythms may interact with metabolism to shape the body’s response to food contaminants. Additional studies are needed to develop precision nutrition strategies that align eating patterns with natural circadian rhythms to optimize the detoxification of food contaminants.

Citation: Kunde H, Ioannou EI, Chovatiya J, Jagani R, Charisiadis P, Arora M, Andra SS, Makris KC. 2025. An exposomics analysis of 125 biomarkers of exposure to food contaminants and biomarkers of oxidative stress: a randomized cross-over chrononutrition trial of healthy adults. Environ Int 202:109682.

Optimizing a one-step treatment for water decontamination

A modeling approach provides new mechanistic insights into designing catalytic nanofiltration membranes for water treatment, according to an NIEHS-supported study.

Catalytic nanofiltration membranes are a one-step technology that can remove a variety of contaminants from water. These membranes consist of tiny pores, each smaller than a nanometer, which filter out inorganic salts and metals. They also contain catalysts that break down small organic compounds, including certain pesticides and pharmaceuticals. However, their use has been limited because it is unclear how catalytic reactions interact with solute mass transport — the movement of dissolved substances through the membrane.

To overcome this limitation, the researchers used a modeling method that integrates mass transport and catalytic reactions. They found that contaminant degradation is optimized when oxidants — substances that help break down contaminants upon catalytic activation — are efficiently transported through the membrane.

The study also showed that catalyst placement matters. Catalysts on the membrane surface perform best when solute mass transport is relatively fast. Catalysts embedded in the membrane perform better when oxidants are properly distributed within the membrane pores. In addition, choosing the right combinations of oxidants and catalysts can further boost the performance of membranes.

According to the researchers, the findings provide a roadmap for designing more efficient, one-step water treatment technologies that can remove contaminants while minimizing secondary pollution.

Citation: Duan Y, Wang R, Shocron AN, Elimelech M. 2025. Design principles of catalytic reactive membranes for water treatment. Nature Water 3:949-62.

Air pollution gases may trigger stress response tied to heart disease

Exposure to volatile organic compounds (VOCs) may overstimulate the body’s fight-or-flight response, offering a potential explanation for how these air pollutants contribute to cardiovascular disease, according to an NIEHS-supported study.

Air pollution causes an estimated nine million deaths worldwide each year and is a major contributor to cardiovascular disease. Polluted air often contains VOCs — carbon-based chemicals that evaporate easily and are emitted from sources such as vehicles, industrial processes, and household products. Compared to particulate air pollution, less is known about the health impact of VOCs and how they might increase the risk of cardiovascular disease.

In the new study, the researchers examined whether the activation of the sympathetic nervous system (SNS) — also known as the fight-or-flight response — might play a role, because prolonged SNS activity can lead to chronic stress and cardiovascular problems. The researchers recruited 696 adults in Louisville, Kentucky and analyzed urinary metabolites of VOCs and neurotransmitters that indicate a hyperactive SNS. The results revealed that higher concentrations of VOC metabolites were associated with higher levels of the neurotransmitters epinephrine, norepinephrine, dopamine, and serotonin.

According to the researchers, the findings provide new insights into the potential health effects of exposure to a major constituent of air pollution.

Citation: Stopforth CK, Sears C, Gao H, Riggs DW, Srivastava S, Krivokhizhina T, Hart JL, et al. 2025. Associations of sympathetic activation with exposure to volatile organic compounds: a cross-sectional study. Environ Res 285(Pt 2):122451.

PFAS may reduce long-term benefits of weight-loss surgery in teens

The long-term effectiveness of weight-loss surgery may be diminished in adolescents with higher presurgical levels of per- and polyfluoroalkyl substances (PFAS), according to an NIEHS-supported study.

Obesity is a major public health challenge among children and adolescents, increasing their risk of cardiovascular disease and type 2 diabetes. Severe obesity among teens has become more common in recent years, and bariatric surgery (weight-loss) surgery can be an effective treatment. However, many of these patients regain weight within one year, for reasons that are unclear.

To investigate, the researchers focused on the potential role of PFAS, which are widely used, persistent chemicals that accumulate in the body and can disrupt hormones and metabolic processes. Past studies have shown that high PFAS levels may reduce the effectiveness of weight-loss diets in adults. In the new study, the team measured baseline levels of seven PFAS in 186 adolescents undergoing bariatric surgery. They found that higher plasma concentrations of three PFAS — PFOS, PFHxS, and PFHpS — were associated with greater body mass index regain, reduced percent weight loss, and increased waist circumference from 1-5 years after bariatric surgery.

According to the authors, the findings may inform strategies to enhance the long-term success of bariatric surgery and improve health outcomes among adolescents.

Citation: Baumert BO, Costello E, Li Z, Ryder JR, Inge T, Jenkins T, Sisley S, et al. 2025. PFAS exposure and postoperative weight regain in adolescents after bariatric surgery: findings from the Teen-LABS Study. Obesity (Silver Spring); doi: 10.1002/oby.70009 [online 4 Aug ahead of print].

Indoor air pollution may disrupt a child’s sleep

High levels of indoor fine particulate matter (PM2.5) are associated with sleep problems among low-income children, according to a study supported by NIEHS and the National Heart, Lung, and Blood Institute.

Sleep-disordered breathing (SDB) refers to conditions that disrupt normal breathing during sleep. Symptoms include snoring and daytime sleepiness, and the condition is linked to health problems such as high blood pressure and cognitive impairment. SDB disproportionately affects people living in disadvantaged neighborhoods, and many children may be at heightened risk. Although previous research has connected outdoor air pollution to SDB, few studies have examined the potential role of indoor air pollution — where children spend a significant portion of their time.

In the new study, researchers assessed the relationship between SDB and indoor PM2.5 levels of 260 children ages 6-12 years living in predominantly low-income neighborhoods in Boston. They found that exposure to higher concentrations of PM2.5 was associated with more than a three-fold increase in the risk of SDB. The air pollutant was also linked to higher odds of loud snoring.

The findings suggest that poor indoor air quality may be an under-appreciated contributor to SDB and snoring among children and may help explain higher rates of sleep disorders among people who reside in disadvantaged neighborhoods. The authors note that more research is needed to identify the specific sources of indoor air pollution that may be driving these patterns.

Citation: Wang J, Gueye-Ndiaye S, Castro-Diehl C, Bhaskar S, Li L, Tully M, Rueschman M, Owens J, Gold DR, Chen J, Phipatanakul W, Adamkiewicz G, Redline S. 2025. Associations between indoor fine particulate matter (PM2.5) and sleep-disordered breathing in an urban sample of school-aged children. Sleep Health 11(4):408-14.

How fine particulate matter may worsen Alzheimer’s disease

Autopsy data clarify how fine particulate matter (PM2.5) may increase the risk of dementia and cognitive decline, according to a new NIEHS-supported study.

Previous research has linked PM2.5 exposure with a higher risk of dementia and poorer cognitive function. However, the biological mechanisms that mediate this relationship have remained unclear.

To answer this question, the researchers analyzed data from 602 autopsy examinations, considered the most accurate method for diagnosing Alzheimer’s disease and related dementias. They also estimated exposure to ambient PM2.5 one year before death using high-resolution air pollution data matched to each participant’s residential address.

The results showed that higher PM2.5 exposure was associated with greater cognitive and functional impairment. It was also linked to a higher chance of more severe Alzheimer’s disease-related changes, such as the buildup of amyloid plaques and abnormal tau proteins. Moreover, these changes in the brain accounted for 63% of the relationship between PM2.5 exposure and cognitive or functional decline.

As the authors noted, the findings suggest that PM2.5 may contribute to Alzheimer’s disease progression by increasing brain vulnerability, offering new insight into the underlying mechanisms. However, additional studies are needed to replicate the findings in larger populations.

Citation: Kim B, Blam K, Elser H, Xie SX, Van Deerlin VM, Penning TM, Weintraub D, Irwin DJ, Massimo LM, McMillan CT, Mechanic-Hamilton D, Wolk DA, Lee EB. 2025. Ambient air pollution and the severity of Alzheimer disease neuropathology. JAMA Neurol 82(11):1153-61.

Persistent organic pollutants may impair thyroid function

Long-lasting chemicals — including some banned in the U.S. due to toxicity — may continue to influence thyroid hormones in Hispanic/Latino adults, according to researchers supported in part by NIEHS.

Persistent organic pollutants (POPs) are toxic, human-made chemicals that remain in the environment for decades and accumulate in living organisms. Certain POPs — such as organochlorine pesticides (OCPs), brominated flame retardants, and banned chemicals called polychlorinated biphenyls (PCBs) — have been associated with diabetes and high blood pressure. Even though thyroid function plays an important role in the development of these conditions, the effects of POPs on thyroid hormones have not been thoroughly investigated. This is especially relevant to aging Hispanic/Latino adults, who tend to have higher levels of certain hormone-disrupting chemicals and are more prone to cardiovascular and metabolic disorders.

The researchers evaluated POP concentrations and thyroid function among 1,073 middle-aged to older men and 716 postmenopausal women participating in a multi-site U.S. study of diverse Hispanic/Latino populations.

The team found notable sex-specific patterns. Among postmenopausal women, brominated flame retardants, but not PCBs, were associated with thyroid-related hormones. In contrast, among men, thyroid-related hormones were linked to PCBs and OCPs with weaker associations observed with brominated flame retardants.

According to the authors, these findings highlight the potential for POPs to influence thyroid hormone regulation and underscore the need for additional research to inform interventions to prevent these thyroid-related chronic conditions in Hispanic/Latino communities.

Citation: Abasilim C, Persky V, Sargis RM, Day T, Tsintsifas K, Daviglus M, Cai J, Freels S, Grieco A, Peters BA, Isasi CR, Talavera GA, Thyagarajan B, Davis M, Jones R, Sjodin A, Turyk ME. 2025. Associations between persistent organic pollutants and thyroid-related hormones and homeostasis parameters in middle-aged to older men and postmenopausal women: The HCHS/SOL. Environ Res 285(Pt 4):122584.

Evaluating the health impact of extreme temperature events

A new method that provides accurate, high-resolution estimates of extreme temperature events could advance precision health applications, according to researchers supported in part by NIEHS.

Exposure to extreme heat or cold may increase the risk of health problems, such as cardiovascular disease, respiratory illnesses, heat exhaustion, and heatstroke, especially among older adults and young children. To understand these health effects, it is critical to accurately measure exposure to extreme events. However, such measures are not standardized across agencies, and many datasets lack the spatial detail needed to support health research.

To address this need, the researchers developed a new approach that measures exposure to extreme heat and cold events at a high-spatial resolution of 500 by 500 meters. The method, called Grid EXposure (GridEX), enables individual-level health data to be evaluated across multiple spatial scales. In addition, GridEX automates the collection of data from weather stations and estimates thermal comfort and perceived temperature. Importantly, it can be combined with health datasets across geographic locations, helping to identify specific populations that should be prioritized for public health interventions.

Citation: Fard P, Hügel J, Keivabu RC, Dominici F, Zagheni E, Estiri H, Patel CJ. 2025. Developing a spatiotemporal repository of extreme heat and cold exposure in the United States for precision public health research. Environ Sci Technol 59(37):19872-84.