U.S. preschoolers exposed to broad range of potentially harmful chemicals

Findings concern researchers because early childhood is a critical period for brain and body development

University of California - Davis Health

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(SACRAMENTO, Calif.) — A national study published in Environmental Science & Technology finds children aged 2 to 4 years in the United States are routinely exposed to a broad range of potentially harmful chemicals. Many of the chemicals the researchers identified are not routinely monitored and may pose health risks.

The research was conducted by multiple institutions across the United States in coordination with the Environmental influences on Child Health Outcomes (ECHO), a program supported by the National Institutes of Health (NIH).

The researchers analyzed urine samples from 201 children aged 2 to 4 years. They tested for 111 chemicals. Their study found:

• 96 chemicals were detected in at least five children.
• 48 chemicals were found in over half of the children.
• 34 chemicals were detected in more than 90% of children — including nine chemicals not currently tracked in national health surveys like the National Health and Nutrition Examination Survey (NHANES).

“Our study shows that childhood exposure to potentially harmful chemicals is widespread. This is alarming because we know early childhood is a critical window for brain and body development,” said Deborah H. Bennett, lead author and UC Davis professor in the Department of Public Health Sciences. “Many of these chemicals are known or suspected to interfere with hormones, brain development and immune function.”

Children exposed to chemicals through everyday activities

The NIH-funded ECHO Cohort combines data from pregnancy and pediatric cohorts to examine the impacts of early environmental exposures on child health and development. This study looked at samples of 201 children from four states (California, Georgia, New York and Washington).

The researchers looked for childhood exposure to common environmental chemicals, including:

• Phthalates and phthalate alternatives used in plastics like toys and food packaging, as well as personal care products and household items.
• Parabens commonly used in cosmetics, lotions, shampoos and pharmaceuticals.
• Bisphenols found in plastic containers, food can linings and thermal paper receipts.
• Benzophenones found in sunscreens, cosmetics and plastics.
• Pesticides used in agricultural and residential pest control.
• Organophosphate esters (OPEs) used as flame retardants in furniture and building materials and as plasticizers in food packaging.
• Polycyclic aromatic hydrocarbons (PAHs), byproducts of combustion found in vehicle exhaust, grilled foods and tobacco smoke.
• Bactericides found in antibacterial soaps and personal care products.

Children are exposed to these environmental chemicals through everyday activities, such as eating, drinking, breathing indoor and outdoor air and touching contaminated surfaces.

Frequent hand-to-mouth contact, playing close to the ground, and higher intake rates relative to their smaller body weight make kids especially vulnerable to chemical exposure.

Trends and disparities

In addition to the widespread exposure, the researchers noted some trends.

• Levels of triclosan, parabens, PAHs and most phthalates decreased over the years the samples were collected (from 2010 to 2021).
• An alternative plasticizer, DINCH (di-iso-nonyl-cyclohexane-1,2-dicarboxylic acid), and emerging pesticides, such as the neonicotinoid acetamiprid, pyrethroid pesticides, and the herbicide 2,4-D, showed an upward trend.
• Firstborn children had significantly lower chemical levels than their younger siblings.
• Chemical levels were often higher in younger children (age 2) than in 3- or 4-year-olds.
• Children from racial and ethnic minority groups had higher levels of parabens, several phthalates and PAHs.

Most of the children’s mothers had provided urine samples during pregnancy. This allowed the researchers to analyze the chemicals in the mother’s urine with the chemicals in the children’s urine.

They found the children had higher levels of several chemicals than their mothers did during pregnancy. These included two phthalates, bisphenol S (often used as a BPA replacement) and the pesticide biomarkers 3-PBA and trans-DCCA.

Need for more monitoring and regulation

The researchers emphasize that further studies are necessary to comprehend the long-term health implications of these chemicals.

“Exposure to certain chemicals in early childhood — such as pesticides, plasticizers and flame retardants — has been linked to developmental delays, hormone disruption and other long-term health issues,” said Jiwon Oh, first author of the study and a postdoctoral scholar in the UC Davis Department of Public Health Sciences. “This new study highlights the urgent need for expanded biomonitoring and stronger regulations to protect children from harmful exposures.”

A complete list of authors and funders appears in the paper.

How to limit chemical exposure

It is impossible to eliminate all chemical exposures. Yet, there are many simple steps parents can take to help reduce their children’s contact with harmful chemicals.

1. Choose safer products: Look for “phthalate-free,” “paraben-free” and “fragrance-free” labels.
2. Avoid plastics labeled #3, #6, and #7: These may contain BPA or similar chemicals.
3. Wash hands frequently, especially before eating.
4. Ventilate your home and use HEPA filters, when possible.
5. Limit pesticide exposure: Wash produce thoroughly and consider organic options.
6. Clean regularly: Use a damp cloth to reduce dust that may contain chemical residues.

Resources

• Read the study
• Residents in San Joaquin Valley breathe chemical pesticides, according to new study
• Exposure to flame retardants linked to premature birth, higher birth weight
• How much is the dust in your home affecting your child?

 

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Journal

Environmental Science & Technology

DOI

10.1021/acs.est.4c13605 

Method of Research

Data/statistical analysis

Subject of Research

People

Article Title

Exposures to Contemporary and Emerging Chemicals among Children Aged 2 to 4 Years in the United States Environmental Influences on the Child Health Outcome (ECHO) Cohort Click to copy a

Article Publication Date

30-Jun-2025

COI Statement

The authors declare the following competing financial interest(s): RJS consults for Beasley Law, Inc. RJS has received travel support to present at the 35th Annual Meeting of the Organization of Teratology Information Specialists (OTIS). RJS and DHB consult for Linus Biotechnology, Inc. The remaining authors have no conflicts of interest to report.

 

Pair of malaria parasite proteins could lead to targeted therapies

UC Riverside-led team identifies essential gene regulators in deadly malaria parasite

University of California - Riverside

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RIVERSIDE, Calif. -- A University of California, Riverside-led team has made an advance in the basic understanding of Plasmodium falciparum, the parasite responsible for the deadliest form of human malaria, that could make novel, highly targeted anti-malarial therapies possible.

Led by Karine Le Roch, a professor of molecular, cell and systems biology, the team identified two key proteins inside the “apicoplast” — a unique, parasite-specific organelle found in P. falciparum — that control gene expression. These proteins belong to the RAP (RNA-binding domain Abundant in Apicomplexans) family of proteins. Far more numerous in parasites than in humans, RAP proteins play critical roles in regulating RNA molecules and translating them into proteins inside parasite organelles.

Using advanced genetic tools, the team created knockdown strains of P. falciparum to selectively deactivate the two RAP proteins, PfRAP03 and PfRAP08. The team found the loss of either protein led to parasite death, confirming their essential roles.

The researchers also discovered that PfRAP03 and PfRAP08 specifically bind to ribosomal RNA (rRNA) and transfer RNA (tRNA) molecules, respectively. These non-coding RNAs are fundamental to protein synthesis within the apicoplast.

“This is the first time anyone has shown how RAP proteins in the apicoplast directly interact with rRNA and tRNA,” said Le Roch, who directs the UCR Center for Infectious Disease Vector Research. “We’ve now shown mechanistically how these proteins regulate translation in an organelle that’s completely foreign to the human body.”

Le Roch explained that humans have six RAP proteins, but parasites like Plasmodium have more than 20. 

“This evolutionary expansion suggests that RAP proteins may perform parasite-specific functions, making them exciting drug targets,” she said.

The study, published in Cell Reports, builds on the team’s previous research on RAP proteins in parasite mitochondria and represents the first detailed mechanistic analysis of their function in the apicoplast. 

Unlike any structure found in human cells, the apicoplast is unique to apicomplexan parasites — a large group of single-celled organisms that includes Plasmodium, Toxoplasma gondii, and Babesia. This uniqueness makes it an ideal target for therapies that can eliminate the parasite without harming the human host.

“While the focus of our paper is malaria, the implications extend to other apicomplexan diseases like toxoplasmosis — dangerous especially to pregnant women — and babesiosis, a growing tick-borne threat in the United States,” Le Roch said. “This work exposes vulnerabilities across an entire class of parasites, revealing the molecular machinery these parasites rely on. If we can take it apart, we can stop these diseases before they take hold.”

Though no drugs currently target RAP proteins, Le Roch’s lab is working toward solving the 3D structure of these RNA-protein complexes, a crucial step toward structure-guided drug design.

“Our research is a step toward future therapeutic strategies,” Le Roch said. “By targeting essential, parasite-specific proteins that have no human counterparts, we can develop drugs that are both effective and have minimal side effects.”

Le Roch was joined in the study by first author Thomas Hollin, Zeinab Chahine, Steven Abel, Todd Lenz, Jacques Prudhomme, Caitlyn Marie Ybanez, and Anahita S. Abbaszadeh of UCR; Charles Banks and Laurence Florens of the Stowers Institute for Medical Research, Kansas City, Missouri; and Charisse Flerida A. Pasaje and Jacquin C. Niles of the Massachusetts Institute of Technology, Cambridge, Massachusetts.

The research was supported by grants from the National Institute of Allergy and Infectious Diseases of the National Institutes of Health and UCR. 

The research paper is titled “RAP proteins regulate apicoplast noncoding RNA processing in Plasmodium falciparum.”

The University of California, Riverside is a doctoral research university, a living laboratory for groundbreaking exploration of issues critical to Inland Southern California, the state and communities around the world. Reflecting California's diverse culture, UCR's enrollment is more than 26,000 students. The campus opened a medical school in 2013 and has reached the heart of the Coachella Valley by way of the UCR Palm Desert Center. The campus has an annual impact of more than $2.7 billion on the U.S. economy. To learn more, visit www.ucr.edu.

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Journal

Cell Reports

DOI

10.1016/j.celrep.2025.115928 

Method of Research

Experimental study

Subject of Research

Cells

Article Title

RAP proteins regulate apicoplast noncoding RNA processing in Plasmodium falciparum

Article Publication Date

22-Jul-2025

 

Brain stimulation can boost math learning in people with weaker neural connections

Frontoparietal network strength predicts certain math skills and whether brain stimulation can help

PLOS

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image: 

3D volume, generated manually by the authors in CONN, depicting the four frontoparietal seeds (left dlPFC, right dlPFC, left PPC, right PPC) as well as the right and left frontoparietal connectivity that was used in the functional connectivity analyses.

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Credit: Zacharopoulos G et al., 2025, PLOS Biology, CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)

The strength of certain neural connections can predict how well someone can learn math, and mild electrically stimulating these networks can boost learning, according to a study published on July 1st in the open-access journal PLOS Biology by Roi Cohen Kadosh from University of Surrey, United Kingdom, and colleagues.

When it comes to cognitive skills like reading and math, early advantages tend to compound over time. Mathematical abilities, however, seem to plateau from childhood to adulthood, raising the possibility that innate brain characteristics might shape academic outcomes independently of external factors like socioeconomic status. To better understand the neurobiology of mathematical learning, the authors measured connection strength between brain regions associated with learning math while 72 participants performed a 5-day math task. While solving math problems that required either calculating a solution or rote memorization, participants received weak electrical stimulation to either the dorsolateral prefrontal cortex (dlPFC), which plays an important role in executive function and calculations; the posterior parietal cortex (PPC), which is associated with memory recall; or a placebo. They also used magnetic resonance spectroscopy to measure two brain chemicals, glutamate and GABA, that hint at the brain’s current capacity for learning and change.

The researchers found that stronger baseline connectivity between dlPFC, PPC, and the hippocampus — a region involved in long-term memory and in this context, generalizing algorithms across problems — predicted better math performance when participants were asked to calculate the solution, but not when they memorized it. People with weaker connections between the dlPFC and PPC regions improved at calculation learning after electrically stimulating dlPFC. The authors suggest that these results hint at the viability of using brain stimulation to aid math learning in people struggling with biological disadvantages. The authors also identified a complex relationship between neurochemistry, brain plasticity, and communication between regions associated with executive function and memory. Future studies should more deeply examine these relationships, and test whether a neurostimulation approach like this could help people outside of the lab.

Professor Roi Cohen Kadosh, the lead author of the study and Head of the School of Psychology at the University of Surrey, said, “So far, most efforts to improve education have focused on changing the environment – training teachers, redesigning curricula – while largely overlooking the learner’s neurobiology. Yet, a growing body of research has shown that biological factors often explain educational outcomes in mathematics more powerfully than environmental ones. By integrating insights from psychology, neuroscience and education to develop innovative techniques that address these neurobiological constraints, we can help more people reach their potential, broaden access to diverse career pathways and reduce long-term inequalities in income, health and wellbeing.”

 

In your coverage, please use this URL to provide access to the freely available paper in PLOS Biology: http://plos.io/3STohc7

Citation: Zacharopoulos G, Dehghani M, Krause-Sorio B, Near J, Cohen Kadosh R (2025) Functional connectivity and GABAergic signaling modulate the enhancement effect of neurostimulation on mathematical learning. PLoS Biol 23(7): e3003200. https://doi.org/10.1371/journal.pbio.3003200

Author countries: United Kingdom, Canada, United States

Funding: Funding: This research was supported by the European Research Council (Learning&Achievement 338065 to RCK, https://erc.europa.eu/) and the Wellcome Trust (0883781 to RCK, https://wellcome.org/). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

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Journal

PLOS Biology

DOI

10.1371/journal.pbio.3003200 

Method of Research

Experimental study

Subject of Research

People

COI Statement

Competing interests: I have read the journal's policy and the author RCK of this manuscript has the following competing interests: RCK serves on the scientific advisory boards of Neuroelectrics Inc., Innosphere Inc., is the founder and shareholder of Cognite Neurotechnology Ltd., and is an Editorial Board Member at PLOS Biology.

Neurotechnology reverses biological disadvantage in maths learning

University of Surrey

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Roi Cohen Kadosh

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Credit: University of Surrey

Safe, painless, and non-invasive brain stimulation could help people who are at risk of falling behind in maths, according to a new study led by the University of Surrey. 

The study, published in PLoS Biology, found that applying safe electrical currents to the dorsolateral prefrontal cortex (dlPFC) – a region involved in learning and memory, focus, and problem-solving – helped people aged 18 to 30 solve maths problems more efficiently. 

Seventy-two healthy adults took part in a five-day maths training programme – 24 received a form of brain stimulation known as transcranial random noise stimulation (tRNS) to the dlPFC, 24 received tRNS over the posterior parietal cortex and 24 received a placebo (sham) version of the treatment. This allowed researchers to compare the effects of tRNS in different brain regions against a placebo group. 

The study showed, via brain scans, that individuals with stronger brain connectivity between the dlPFC and the posterior parietal cortex performed better in maths learning tasks. They then demonstrated that tRNS over the dlPFC significantly improved learning outcomes for individuals with lower natural brain connectivity between this region and the posterior parietal cortex – a neurobiological profile associated with poorer learning.  

Improvements were also linked to lower levels of GABA – a brain chemical involved in learning. The same research team has previously shown that GABA plays a role in maths learning from childhood to adulthood, including A-level education. 

Professor Roi Cohen Kadosh, the lead author of the study and Head of the School of Psychology at the University of Surrey, said: 

“So far, most efforts to improve education have focused on changing the environment – training teachers, redesigning curricula – while largely overlooking the learner’s neurobiology. Yet, a growing body of research has shown that biological factors often explain educational outcomes in mathematics more powerfully than environmental ones. By integrating insights from psychology, neuroscience and education to develop innovative techniques that address these neurobiological constraints, we can help more people reach their potential, broaden access to diverse career pathways and reduce long-term inequalities in income, health and wellbeing.” 

These findings point to a biological basis for the ‘Matthew effect’ – the tendency for those who start ahead in education to continue advancing, while others fall further behind. The study suggests that targeted brain stimulation could help bridge this gap. 

As the UK looks to boost maths skills across the population, especially in young adults, this basic research and future research on larger samples outside the lab could help shape future policies by showing how tailored support, focusing on brain activity, might make learning fairer and more effective. 

The study was funded by the European Research Council and the Wellcome Trust. 

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Journal

PLOS Biology

DOI

10.1371/journal.pbio.3003200 

Article Title

Functional connectivity and GABAergic signaling modulate the enhancement effect of neurostimulation on mathematical learning

Article Publication Date

1-Jul-2025

Neurotechnology reverses biological disadvantage in maths learning

University of Surrey

Neurotechnology reverses biological disadvantage in maths learning 

Safe, painless, and non-invasive brain stimulation could help people who are at risk of falling behind in maths, according to a new study led by the University of Surrey. 

The study, published in PLoS Biology, found that applying safe electrical currents to the dorsolateral prefrontal cortex (dlPFC) – a region involved in learning and memory, focus, and problem-solving – helped people aged 18 to 30 solve maths problems more efficiently. 

Seventy-two healthy adults took part in a five-day maths training programme – 24 received a form of brain stimulation known as transcranial random noise stimulation (tRNS) to the dlPFC, 24 received tRNS over the posterior parietal cortex and 24 received a placebo (sham) version of the treatment. This allowed researchers to compare the effects of tRNS in different brain regions against a placebo group. 

The study showed, via brain scans, that individuals with stronger brain connectivity between the dlPFC and the posterior parietal cortex performed better in maths learning tasks. They then demonstrated that tRNS over the dlPFC significantly improved learning outcomes for individuals with lower natural brain connectivity between this region and the posterior parietal cortex – a neurobiological profile associated with poorer learning.  

Improvements were also linked to lower levels of GABA – a brain chemical involved in learning. The same research team has previously shown that GABA plays a role in maths learning from childhood to adulthood, including A-level education. 

Professor Roi Cohen Kadosh, the lead author of the study and Head of the School of Psychology at the University of Surrey, said: 

“So far, most efforts to improve education have focused on changing the environment – training teachers, redesigning curricula – while largely overlooking the learner’s neurobiology. Yet, a growing body of research has shown that biological factors often explain educational outcomes in mathematics more powerfully than environmental ones. By integrating insights from psychology, neuroscience and education to develop innovative techniques that address these neurobiological constraints, we can help more people reach their potential, broaden access to diverse career pathways and reduce long-term inequalities in income, health and wellbeing.” 

These findings point to a biological basis for the ‘Matthew effect’ – the tendency for those who start ahead in education to continue advancing, while others fall further behind. The study suggests that targeted brain stimulation could help bridge this gap. 

As the UK looks to boost maths skills across the population, especially in young adults, this basic research, and future research on larger samples outside the lab, could help shape future policies by showing how tailored support, focusing on brain activity, might make learning fairer and more effective. 

The study was funded by the European Research Council and the Wellcome Trust. 

 

[ENDS] 

 

• Roi Cohen Kadosh is available for interview, please contact mediarelations@surrey.ac.uk to arrange.   

• The preview of the paper is available at: https://plos.my.salesforce.com/sfc/p/#U0000000Ifis/a/PM000009bjx3/1ccrJNZ2kD0M4OhdrO1P8wnNttNKa796anHn.htxtoo 

• An image of Roi Cohen Kadosh is available here 

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Journal

PLOS Biology

DOI

10.1371/journal.pbio.3003200 

Sugar, the hidden thermostat in plants

Researchers finally uncover how plants sense heat during the day

University of California - Riverside

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Plants growing in a UC Riverside greenhouse. 

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Credit: Elena Zhukova/UCR

For a decade, scientists have believed that plants sensed temperature mainly through specialized proteins, and mainly at night when the air is cool. New research suggests that during the day, another signal takes over. Sugar, produced in sunlight, helps plants detect heat and decide when to grow.

The study, led by Meng Chen, a University of California, Riverside professor of cell biology, shows that plants rely on multiple heat-sensing systems, and that sugar plays a central and previously unrecognized role in daytime temperature response. The findings, published in Nature Communications, reshape a long-standing view of how plants interact with their environment and could influence future strategies for climate-resilient agriculture.

“Our textbooks say that proteins like phytochrome B and early flowering 3 (ELF3) are the main thermosensors in plants,” Chen said. “But those models are based on nighttime data. We wanted to know what’s happening during the day, when light and temperature are both high because these are the conditions most plants actually experience.”

To investigate, the researchers used Arabidopsis, a small flowering plant favored in genetics labs. They exposed seedlings to a range of temperatures, from 12 to 27 degrees Celsius, under different light conditions, and tracked the elongation of their seedling stems, known as hypocotyls — a classic indicator of growth response to warmth.

They found that phytochrome B, a light-sensing protein, could only detect heat under low light. In bright conditions that mimic midday sunlight, its temperature-sensing function was effectively shut off. Yet, the plants still responded to heat, growing taller even when the thermosensing role of phytochrome B was greatly diminished. That, Chen said, pointed to the presence of other sensors.

One clue came from studies of a phytochrome B mutant lacking its thermosensing function. These mutant plants could respond to warmth only when grown in the light. When grown in the dark, without photosynthesis, they lacked chloroplasts and did not grow taller in response to warmth. But when researchers supplemented the growing medium with sugar, the temperature response returned.

“That’s when we realized sugar wasn’t just fueling growth,” Chen said. “It was acting like a signal, telling the plant that it’s warm.”

Further experiments showed that higher temperatures triggered the breakdown of starch stored in leaves, releasing sucrose. This sugar in turn stabilized a protein known as PIF4, a master regulator of growth. Without sucrose, PIF4 degraded quickly. With it, the protein accumulated but only became active when another sensor, ELF3, also responded to the heat by stepping aside.

“PIF4 needs two things,” Chen explained. “Sugar to stick around, and freedom from repression. Temperature helps provide both.”

The study reveals a nuanced, multi-layered system. During the day, when light is used as the energy source to fix carbon dioxide into sugar, plants also evolved a sugar-based mechanism to sense environmental changes. As temperatures rise, stored starch converts into sugar, which then enables key growth proteins to do their job.

The findings could have practical implications. As climate change drives temperature extremes, understanding how and when plants sense heat could help scientists breed crops that grow more predictably and more resiliently under stress.

“This changes how we think about thermosensing in plants,” Chen said. “It’s not just about proteins flipping on or off. It’s about energy, light, sugar, as well.”

The findings also underscore, once again, the quiet sophistication of the plant world. In the blur of photosynthesis and starch reserves, there’s a hidden intelligence. One that knows, sweetly and precisely, when it’s time to stretch toward the sky.

 

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Journal

Nature Communications

DOI

10.1038/s41467-025-60498-7 

Article Title

A multisensor high-temperature signaling framework for triggering daytime thermomorphogenesis in Arabidopsis

Article Publication Date

1-Jul-2025