Lead (Pb2+) is a well-established neurotoxin that impairs motor, learning, and memory functions, particularly in children and younger adults. However, its impact on older adults remains less understood. Pb2+ toxicity involves disruption of DNA methyltransferase activity and associated epigenetic pathways, potentially altering the expression of specific genes relevant to neurological functions. As methylation patterns naturally shift during aging, Pb2+ exposure may induce additional neurological risks in aged populations. Using a zebrafish model, we investigated the combined effects of Pb2+ exposure and brain aging. Two-year-old male zebrafish were exposed to 1, 10, 100, 1000, 10 000 µg/l Pb2+ or fish water control for five days. Brain tissues were collected for DNA extraction and whole-genome bisulfite sequencing to assess global and gene-specific methylation changes. Our results found that Pb2+ exposures ≥ 100 μg/l significantly increased global methylation levels in the aged brain. Differentially methylated genes (DMGs) exhibited methylation changes within gene body regions and were mostly annotated with ion transportation and signal transduction pathways. Although only a limited number of DMGs showed corresponding changes in gene expression, several of them were associated with locomotor-related functions, including shank1 at 10 000 Pb2+ μg/l, and ptprsa, plxna2, and aopep at 100 μg/l Pb2+. These findings suggest that Pb2+ exposure during aging predominantly induces gene body-localized DNA methylation changes, and the role of such epigenetic regulation in Pb-associated neurobehavioral outcomes warrants further investigation.

1,4-Dioxane, a synthetic volatile organic compound (VOC), has been found in products including paints, cosmetics, and pesticides as well as food products and drinking water. Contamination in groundwater poses significant environmental and public health risks due to its high mobility and widespread human exposure through vapor intrusion and multiroute exposure pathways. Adverse health effects have been observed as a result of exposure to this compound; however, there is little research on the developmental and reproductive effects. Controlled VOC exposures [0.004, 0.40, and 40 parts per million (ppm)] of zebrafish embryos were conducted in sealed glass vials over a developmental period (120 h). Endpoints evaluated were mortality, abnormalities, larval behavior, transcriptomics, and adult-onset effects. The behavior of zebrafish larvae was significantly altered for the 40 ppm group. Expression of key genes (insig1, tbc1d10aa) was observed immediately following exposure and some persisted into adulthood. The top dysregulated diseases and disorders pathways in every concentration were cancer, organismal injury and abnormality, endocrine system disorders, gastrointestinal disease, and neurological disorders. Pathways of note enriched in larval and adult tissues include endocrine gland tumorigenesis, insulin resistance, movement disorders, cell survival, and cellular homeostasis. Specific reproductive pathways included pelvic, genital, uterine, and mammary tumors and carcinomas, however, there was no significant effect on adult zebrafish fertility. This study moves the field forward by integrating a novel zebrafish model and lifespan approach, shedding new light on understudied implications of low-level VOC exposure, ultimately informing public health policies to mitigate the risks associated with this ubiquitous environmental contaminant.

Microplastic (MP) and nanoplastic (NP) pollution has permeated virtually all aspects of life on earth - from high altitude clouds and arctic ice cores to single celled algae and unborn fetuses. Compared to MPs, the ability of NPs to infiltrate biological barriers such as the blood-brain and testes barriers is concerning to human health. Evidence of accumulation across human tissues has accrued, but the long-term health consequences are not well understood. Previously, we exposed zebrafish larvae to environmentally relevant doses of NPs (0-10,000 parts per billion) for five days during early development, reporting NP accumulation, hyperactivity, and disruption of neuromuscular, metabolic, and epigenetic pathways immediately post-exposure. Here, we reared these developmentally exposed animals to adulthood, assessing reproductive capacity, offspring neurobehavior, and transcriptomics of brain and gonadal tissue for comparison. NP exposure impaired reproduction in adulthood: while high level exposure profoundly reduced overall spawning capacity, intermediate exposure also decreased fertilization of elicited eggs. Surviving offspring from the intermediate group were also hyperactive, like their parents, demonstrating a persistent and heritable neurobehavioral phenotype. Overall, far more significantly differentially expressed genes were found in adult tissues than in larvae; however, larval disruption of endocrine and neurological disease pathways persisted into adulthood. While female transcriptomics suggested recovery from early life NP exposure, male tissues were deleteriously and disproportionately affected. Male transcriptomics implicated neuromuscular and neurodegenerative diseases, endocrine disruption, and cancer. Oxidative stress was a consistently present mechanism underlying persistent disruption and adult-onset pathologies.

Exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), an environmental endocrine disruptor and model AhR agonist, is linked to skeletal abnormalities, cardiac edema, stunted growth rate, altered metabolism, and neurobehavioral deficits. We have previously reported transgenerational reproductive outcomes of developmental TCDD exposure in adult zebrafish (Danio rerio), an NIH-validated model for developmental and generational toxicology. Using the same paradigm of sublethal TCDD exposure (50 pg/ml) at both 3 and 7 weeks post fertilization (wpf), we investigated several novel endpoints, including longitudinal morphometrics and anxiety-linked behavior, in fish exposed as juveniles. We also assessed developmental abnormalities and neurobehavior in their F1 larval offspring. TCDD exposure induced timepoint-dependent decreases in several craniofacial and trunk morphometrics across juvenile development. In early adulthood, however, only exposed males underwent a transient period of compensatory growth, ending between 7 and 12 months post fertilization (mpf). At 12 mpf, exposed adult fish of both sexes displayed increased exploratory behaviors in a novel tank test. The F1 offspring of parents exposed at both 3 and 7 wpf were hyperactive, but neurobehavioral outcomes diverged depending on parental exposure window. F1 exposure-lineage larvae had increased rates of edema and skeletal abnormalities, but fewer unhatched larvae compared to controls. Parent- and timepoint-specific effects of exposure on abnormality rate were also evaluated; these outcomes were considerably less severe. Our novel behavioral findings expand current knowledge of the long-term and intergenerational consequences of early-life TCDD exposure in a zebrafish model, in addition to delineating minor longitudinal morphometric changes in exposed fish and abnormalities in larval offspring.

Lead (Pb) is a well-known neurotoxin with established adverse effects on the neurological functions of children and younger adults, including motor, learning, and memory abilities. However, its potential impact on older adults has received less attention. Using the zebrafish model, our study aims to characterize the dose–response relationship between environmentally relevant Pb exposure levels and their effects on changes in behavior and transcriptomics during the geriatric periods. We exposed two-year-old zebrafish to waterborne lead acetate (1, 10, 100, 1000, or 10,000 µg/L) or a vehicle (DMSO) for 5 days. While lower concentrations (1–100 µg/L) reflect environmentally relevant Pb levels, higher concentrations (1000–10,000 µg/L) were included to assess acute toxicity under extreme exposure scenarios. We conducted adult behavior assessment to evaluate the locomotor activity following exposure. The same individual fish were subsequently sacrificed for brain dissection after a day of recovery in the aquatic system. RNA extraction and sequencing were then performed to evaluate the Pb-induced transcriptomic changes. Higher (1000–10,000 ug/L) Pb levels induced hyperactive locomotor patterns in aged zebrafish, while lower (10–100 ug/L) Pb levels resulted in the lowest locomotor activity compared to the control group. Exposure to 100 µg/L led to the highest number of differentially expressed genes (DEGs), while 10,000 µg/L induced larger fold changes in both directions. The neurological pathways impacted by Pb exposure include functions related to neurotransmission, such as cytoskeletal regulation and synaptogenesis, and oxidative stress response, such as mitochondrial dysfunction and downregulation of heat shock protein genes. These findings emphasize a U-shape dose–response relationship with Pb concentrations in locomotor activity and transcriptomic changes in the aging brain.

Urban environments are afflicted by mixtures of anthropogenic volatile organic compounds (VOCs). VOC sources that drive human exposure include vehicle exhaust, industrial emissions, and oil spillage. The highly volatile VOC benzene has been linked to adverse health outcomes. However, few studies have focused on the later-in-life effects of low-level benzene exposure during the susceptible window of early development. Transcriptomic responses during embryogenesis have potential long-term consequences at levels equal to or lower than 1 ppm, therefore justifying the analysis of adult zebrafish that were exposed during early development. Previously, we identified transcriptomic alteration following controlled VOC exposures to 0.1 or 1 ppm benzene during the first five days of embryogenesis using a zebrafish model. In this study, we evaluated the adult-onset transcriptomic responses to this low-level benzene embryogenesis exposure (n = 20/treatment). We identified key genes, including col1a2 and evi5b, that were differentially expressed in adult zebrafish in both concentrations. Some DEGs overlapped at the larval and adult stages, specifically nfkbiaa, mecr, and reep1. The observed transcriptomic results suggest dose- and sex-dependent changes, with the highest impact of benzene exposure to be on cancer outcomes, endocrine system disorders, reproductive success, neurodevelopment, neurological disease, and associated pathways. Due to molecular pathways being highly conserved between zebrafish and mammals, developmentally exposed adult zebrafish transcriptomics is an important endpoint for providing insight into the long term-effects of VOCs on human health and disease.

Despite growing urbanization, our understanding of the impacts of water and sanitation on human health has largely come from studies in rural sectors. To this end, we collected data at both regional (water quality measures from water treatment systems) and community (cross-sectional surveys) scales to examine determinants of enteric pathogen infection and diarrheal disease among infants in Addis Ababa, Ethiopia. Regionally, the Legedadi water treatment plant had significantly lower heterotrophic plate counts, total coliform counts, and fecal coliform counts compared with the Gefersa water treatment plant. The number of pathogen types in infant stool also differed by plant. Decreases in chlorine levels and increases in the relative abundance of Gammaproteobacteria with distance from treatment plants suggest a compromised water distribution system. In communities, infants in households that obtained water from yard pipes or public taps had significantly lower odds of diarrhea compared to households that had water piped into their dwellings (OR = 0.35, 95% CI 0.16, 0.76, and OR = 0.39, 95% CI 0.15, 1.00, respectively). Similarly, infants in households that boiled or filtered water had significantly lower odds of diarrhea compared to households that did not treat water (OR = 0.40, 95% CI 0.19, 0.86 and OR = 0.23, 95% CI 0.06, 0.84, respectively). Integrating multiscalar data better informs the health impacts of water in urban settings.

Per- and polyfluoroalkyl substances (PFASs) are ubiquitous in the environment and are tied to myriad health effects. Despite the phasing out of the manufacturing of two types of PFASs (perfluorosulfonic acid (PFOS) and perfluorooctanoic acid (PFOA)), chemical composition renders them effectively indestructible by ambient environmental processes, where they thus remain in water. Exposure via water can affect both human and aquatic wildlife. PFASs easily cross the placenta, exposing the fetus at critical windows of development. Little is known about the effects of low-level exposure during this period; even less is known about the potential for multi- and transgenerational effects. We examined the effects of ultra-low, very low, and low-level PFAS exposure (7, 70, and 700 ng/L PFOA; 24, 240, 2400 ng/L PFOS; and stepwise mixtures) from 0–5 days post-fertilization (dpf) on larval zebrafish (Danio rerio) mortality, morphology, behavior and gene expression and fecundity in adult F0 and F1 fish. As expected, environmentally relevant PFAS levels did not affect survival. Morphological abnormalities were not observed until the F1 and F2 generations. Behavior was affected differentially by each chemical and generation. Gene expression was increasingly perturbed in each generation but consistently showed lipid pathway disruption across all generations. Dysregulation of behavior and gene expression is heritable, even in larvae with no direct or indirect exposure. This is the first report of the transgenerational effects of PFOA, PFOS, and their mixture in terms of zebrafish behavior and untargeted gene expression.

Triclosan, triclocarban and 4-nonylphenol are all chemicals of emerging concern found in a wide variety of consumer products that have exhibited a wide range of endocrine-disrupting effects and are present in increasing amounts in groundwater worldwide. Results of the present study indicate that exposure to these chemicals at critical developmental periods, whether long-term or short-term in duration, leads to significant mortality, morphologic, behavioral and transcriptomic effects in zebrafish (Danio rerio). These effects range from total mortality with either long- or short-term exposure at 100 and 1000 nM of triclosan, to abnormalities in uninflated swim bladder seen with long-term exposure to triclocarban and short-term exposure to 4-nonylphenol, and cardiac edema seen with short-term 4-nonylphenol exposure. Additionally, a significant number of genes involved in neurological and cardiovascular development were differentially expressed after the exposures, as well as lipid metabolism genes and metabolic pathways after exposure to each chemical. Such changes in behavior, gene expression, and pathway abnormalities caused by these three known endocrine disruptors have the potential to impact not only the local ecosystem, but human health as well.

Urban environments are plagued by complex mixtures of anthropogenic volatile organic compounds (VOCs), such as mixtures of benzene, toluene, ethylene, and xylene (BTEX). Sources of BTEX that drive human exposure include vehicle exhaust, industrial emissions, off-gassing of building material, as well as oil spillage and leakage. Among the BTEX mixture, benzene is the most volatile compound and has been linked to numerous adverse health outcomes. However, few studies have focused on the effects of low-level benzene on exposure during early development, which is a susceptible window when hematological, immune, metabolic, and detoxification systems are immature. In this study, we used zebrafish to conduct a VOC exposure model and evaluated phenotypic and transcriptomic responses following 0.1 and 1 ppm benzene exposure during the first five days of embryogenesis (n = 740 per treatment). The benzene body burden was 2 mg/kg in 1 ppm-exposed larval zebrafish pools and under the detection limit in 0.1 ppm-exposed fish. No observable phenotypic changes were found in both larvae except for significant skeletal deformities in 0.1 ppm-exposed fish (p = 0.01) compared with unexposed fish. Based on transcriptomic responses, 1 ppm benzene dysregulated genes that were implicated with the development of hematological system, and the regulation of oxidative stress response, fatty acid metabolism, immune system, and inflammatory response, including apob, nfkbiaa, serpinf1, foxa1, cyp2k6, and cyp2n13 from the cytochrome P450 gene family. Key genes including pik3c2b, pltp, and chia.2 were differentially expressed in both 1 and 0.1 ppm exposures. However, fewer transcriptomic changes were induced by 0.1 ppm compared with 1 ppm. Future studies are needed to determine if these transcriptomic responses during embryogenesis have long-term consequences at levels equal to or lower than 1 ppm.

This study investigates the pesticides atrazine, chlorpyrifos, and dieldrin for endocrine disrupting, phenotypic, and neurobehavioral effects. Zebrafish embryos were exposed to various environmentally relevant concentrations of pesticides during two critical windows, 0-5 days post fertilization (dpf) throughout embryogenesis and 4-5 dpf at early larval development. The toxicity of each chemical and concentration was then determined by evaluating developmental abnormalities, behavioral alterations, and transcriptomic changes. We found the most significant outcomes resulted from dieldrin exposures as low as 1 nM at 0-5 dpf, or 0.1 nM at 4−5 dpf, including abnormalities in skeleton, swim bladder, and yolk sec, as well as hyperactive behavioral phenotypes. Following dieldrin exposures at higher concentrations, 100 nM at 0-5 dpf and 1000 nM at 4−5 dpf, we observed startle movements at the transition between light and dark stimulus. The transcriptomic changes of high-level dieldrin exposures (1000 nM) implicated movement or seizure disorders. Atrazine at concentrations equal or above 100 nM led to underinflated swim bladders following exposure at 0-5 dpf. Both atrazine exposure paradigms showed transcriptomic changes related to neurological disorders and breast cancer. All chlorpyrifos exposures showed no significant morphological abnormalities and the fewest differentially expressed genes, suggesting chlorpyrifos at 0.01-100 nM exhibited the lowest toxicity among these three pesticides.

Activated carbon block (ACB) point-of-use (PoU) drinking water filters can change the bacterial composition in drinking water. Consuming ACB PoU filtered water may also influence gut microbiomes. This study uses the zebrafish model to evaluate how the ACB PoU filter affects the gut microbiomes and phenotypic responses in larvae and adulthood. An ACB PoU filter manifold system was constructed to feed larval and adult zebrafish tap and filtered water at the early and late stages of the filter operation period. Adult zebrafish gut microbiomes were not affected by exposure to water types and filter stages. Unlike the adult, gut microbiomes of the larvae exposed to filtered water at the late stage of filter operation were dominated by more filter-relevant bacterial taxa, including Comamonadaceae and Brevundimonas, than the early stage-filtered-water- and tap water-exposed larvae. We also found some fish that were either exposed to filtered water at early and late stages or tap water supplied to the filter toward the end of the experiment showed hyperactive locomotion behaviour, and had significantly lower relative abundances of a Pseudomonas spp. (OTU3) than the normally behaved fish. Our findings indicate that ACB PoU filtered water can alter gut microbiomes and affect the behaviour patterns in larval zebrafish.

Identifying the breakthrough pattern of drinking water bacteria through faucet-mounted activated carbon block filters at the point of use using abiotic microspheres and biotic surrogates, fluorescent-tagged E. coli and P. aeruginosa.

Metformin is found in the majority of lakes and streams in the United States, leading to widespread environmental exposure. Results of the present study indicate that extended duration metformin exposure at critical developmental periods leads to decreased survival rates in zebrafish (danio rerio), an NIH approved human model. Significant abnormalities are seen with extended duration metformin exposure from 4 h post fertilization up to 5 days post fertilization, although short term metformin exposure for 24 h at 4-5 days post fertilization did not lead to any significant abnormalities. Both extended and short term duration did however have an impact on locomotor activity of zebrafish, and several genes involved in neurological and cardiovascular development were differentially expressed after exposure to metformin. The changes seen in behavior, gene expression and morphological abnormalities caused by metformin exposure should be examined further in future studies in order to assess their potential human health implications as metformin prescriptions continue to increase worldwide.

Estrone and BPA are two endocrine disrupting chemicals (EDCs) that are predicted to be less potent than estrogens such as 17β-estradiol and 17α-ethinylestradiol. Human exposure concentrations to estrone and BPA can be as low as nanomolar levels. However, very few toxicological studies have focused on the nanomolar-dose effects. Low level of EDCs can potentially cause non-monotonic responses. In addition, exposures at different developmental stages can lead to different health outcomes. To identify the nanomolar-dose effects of estrone and BPA, we used zebrafish modeling to study the phenotypic and transcriptomic responses after extended duration exposure from 0 to 5 days post-fertilization (dpf) and short-term exposure at days 4-5 post fertilization. We found that non-monotonic transcriptomic responses occurred after extended duration exposures at 1 nM of estrone or BPA. At this level, estrone also caused hypoactivity locomotive behavior in zebrafish. After both extended duration and short-term exposures, BPA led to more apparent phenotypic responses, i.e. skeletal abnormalities and locomotion changes, and more significant transcriptomic responses than estrone exposure. After short-term exposure, BPA at concentrations equal or above 100 nM affected locomotive behavior and changed the expression of both estrogenic and non-estrogenic genes that are linked to neurological diseases. These data provide gaps of mechanisms between neurological genes expression and associated phenotypic response due to estrone or BPA exposures. This study also provides insights for assessing the acceptable concentration of BPA and estrone in aquatic environments.

Activated carbon based point-of-use drinking water filters change the bacterial community structure and increase the absolute abundance of genera, including those associated with opportunistic pathogens.