The study drew on 289 children enrolled in the PROGRESS cohort in Mexico, a long-running birth cohort designed to examine how environmental exposures shape child health. Rather than relying on blood or urine samples, which capture only recent exposure, the researchers turned to deciduous teeth, the baby teeth that children naturally shed. Teeth grow in layers much like tree rings, and the dentine that forms during specific developmental periods locks in a chemical record of what circulated in the child’s bloodstream at the time. By segmenting dentine along growth lines, the team was able to retrospectively quantify arsenic exposure for every week from sixteen weeks before birth through fourteen weeks after birth, an unprecedented temporal resolution for an immunotoxicology study.

When the children returned for a follow-up visit around age four to five, the investigators measured serum levels of immunoglobulin G antibodies directed against six vaccine antigens: measles, mumps, and rubella from the MMR vaccine, and diphtheria, tetanus, and pertussis from the DTP series. These antibodies are the immune system’s memory of vaccination, the molecular shield that prevents re-infection, and their concentrations in blood are a standard benchmark of how well a vaccine has taken hold. The measurements were performed using a multiplexed Luminex bead-based immunoassay, a technique that allows all six antibody targets to be quantified simultaneously from a small serum sample.

The statistical challenge was considerable. Because arsenic exposure was estimated for thirty consecutive weeks, the researchers needed a method that could detect when in that timeline exposure mattered, not just whether it mattered overall. They employed Distributed Lag Non-linear Models, or DLNMs, a framework originally developed in environmental epidemiology for studying delayed and time-varying effects of air pollution and temperature. The models related log2-transformed dentine arsenic concentrations to log2-transformed antibody levels across every week of the perinatal period, while adjusting for the child’s age, maternal education, parity, and child sex. The log2 transformation means the reported effects can be read as the change in antibody level associated with a doubling of arsenic exposure during a given week.

The results converged on a single, well-defined period. A doubling of arsenic exposure in the window spanning one week before birth to six weeks after birth was associated with significantly lower anti-measles antibody levels, with an estimated effect of minus 5.62 on the log2 scale and a 95 percent confidence interval running from minus 8.39 to minus 0.83. The same perinatal window showed a significant association for anti-rubella antibodies, with an effect estimate of minus 3.85 and a confidence interval from minus 6.99 to minus 0.63. In practical terms, children with higher arsenic exposure in the weeks surrounding delivery carried measurably weaker antibody defenses against measles and rubella years later, even though their vaccinations occurred long after the exposure itself.

Just as telling was what the analysis did not find. Arsenic exposure during the perinatal window showed no significant association with antibody levels against mumps, diphtheria, tetanus, or pertussis. Nor did earlier or later periods of prenatal and early postnatal exposure produce significant signals for any antigen. This selectivity is biologically intriguing. It suggests that the immune pathways supporting long-term antibody maintenance against measles and rubella may be more sensitive to arsenic’s interference than those supporting the other four antigens, or that different vaccine antigens rely on differently timed developmental programs of B-cell and plasma-cell maturation that vary in their vulnerability to toxic insult.

The timing of the susceptible window makes biological sense. The weeks surrounding birth are a period of profound immunological transition. The fetus must shift from the sterile, maternally protected environment of the womb to an microbe-rich world, and neonatal immune cells are actively learning to distinguish threat from tolerance. Maternal antibodies transferred across the placenta are waning while the infant’s own antibody production is just beginning. Arsenic is known to disrupt immune signaling, generate oxidative stress, and interfere with methylation processes that regulate gene expression, and a toxic exposure during this delicate choreography could plausibly leave a lasting imprint on how well vaccine memory is established and maintained.

The researchers also probed whether the effects differed between boys and girls, or between children who were breastfed at one month postpartum and those who were not, since both factors can shape immune development and arsenic dynamics. They found no heterogeneity by either sex or breastfeeding status, indicating that the association between perinatal arsenic and reduced measles and rubella antibodies appears to operate similarly across these subgroups. That consistency strengthens the case that the finding reflects a general biological vulnerability rather than an effect confined to a particular subset of children.

The methodological innovation deserves particular attention. Traditional exposure assessment in environmental health has long been hampered by the difficulty of reconstructing what a person was exposed to years or decades earlier. Baby teeth offer a solution that is both retrospective and precise, and their use here demonstrates how naturally shed biomaterials can transform the study of developmental toxicology. Combined with the DLNM framework, which treats exposure timing as a variable to be mapped rather than averaged, the approach allowed the team to draw a temporal map of vulnerability with weekly resolution, something conventional single-biomarker studies simply cannot achieve.

The public health implications are significant. Measles remains one of the most contagious human pathogens, and even modest reductions in population-level antibody levels can erode herd immunity and fuel outbreaks, a concern made vivid by recent resurgences of measles in countries where the disease was once controlled. Arsenic contamination of groundwater affects an estimated hundreds of millions of people worldwide, and in regions such as Mexico, where the PROGRESS cohort is based, exposure often begins before birth. If the findings are confirmed in other cohorts, they would add vaccine-preventable disease susceptibility to the long list of harms attributable to early-life arsenic exposure, and they would sharpen the argument for reducing arsenic exposure among pregnant women and newborns, whether through water filtration, dietary interventions, or regulatory limits on contaminated sources. The study, funded by the National Institutes of Health and led by researchers at the Icahn School of Medicine at Mount Sinai together with collaborators at Mexico’s National Institute of Public Health and other institutions, was published open access, with the authors reporting no competing interests.

Subject of Research: Perinatal arsenic exposure and vaccine-specific antibody levels in children

Article Title: Susceptible perinatal windows to arsenic exposure and serum antibody levels in children

Article References: Scotti, A., India-Aldana, S., Martinez, M., Arora, M., McRae, N., Lamadrid-Figueroa, H., Quataert, S. A., Estrada-Gutierrez, G., Torres-Olascoaga, L., Téllez-Rojo, M. M., Wright, R. O., Jusko, T. A., & Colicino, E. (2026). Susceptible perinatal windows to arsenic exposure and serum antibody levels in children. Environmental Health. https://doi.org/10.1186/s12940-026-01331-6

Image Credits: AI Generated

DOI: 10.1186/s12940-026-01331-6

Keywords: arsenic exposure, perinatal window, vaccine antibodies, measles, rubella, immunotoxicology, baby teeth, dentine, PROGRESS cohort, DLNM, humoral immunity, environmental health

The research, led by Shimao Xiong, Naiyi Yin, and Yanshan Cui of the College of Resources and Environment at the University of Chinese Academy of Sciences, together with colleagues at Peking University People’s Hospital, set out to answer a deceptively simple question: does arsenic encountered before or shortly after birth program the gut microbial community in ways that persist or even amplify later in life? To find out, the team built a carefully staged exposure model in C57BL/6J mice, one of the most widely used strains in biomedical research. Pregnant females were given drinking water laced with arsenic at an environmentally relevant concentration of 0.10 milligrams per liter, with exposure beginning either on gestational day zero, before embryos had even implanted, or on gestational day fourteen, during late organogenesis. Exposure then continued through lactation, meaning that pups were dosed both in the womb and through their mother’s milk.

The consequences for growth were immediate and, crucially, dependent on when exposure began. Pups whose mothers started drinking arsenic-contaminated water on gestational day zero showed markedly reduced body weight at weaning, while pups exposed only from gestational day fourteen onward actually gained weight significantly faster than controls. That divergence is more than a curiosity. It implies that the earliest embryonic window, when the foundations of metabolism and organ development are being laid, may be uniquely sensitive to arsenic, whereas later prenatal exposure can steer growth in the opposite direction. Because both groups received the same dose, the timing of exposure, not the amount, was the decisive variable, a conclusion with uncomfortable implications for regulatory standards that typically treat a contaminant as a uniform hazard regardless of developmental stage.

The gut microbiome told an equally nuanced story. When the researchers sequenced the 16S ribosomal RNA genes of bacteria in pup feces at three weeks of age, they found that maternal arsenic exposure had elevated gut microbial diversity in the offspring, a counterintuitive result given that reduced diversity is usually framed as a hallmark of a stressed or dysbiotic gut. Arsenic, it appears, does not simply poison the microbial community; it restructures it, opening ecological space for different species. Whether that restructuring is beneficial, harmful, or neutral depends on which microbes move in, and the study’s longer-term experiments suggest the answer differs between the sexes.

To probe those long-term effects, the team extended the experiment beyond weaning. Some pups received only a five-week high-dose arsenic exposure of 10.0 milligrams per liter during adolescence, a level designed to test the impact of a concentrated later-life hit. Others carried the legacy of early-life low-dose exposure from their mothers and then received the same adolescent high dose. Comparing these groups at eight weeks of age revealed that early-life exposure fundamentally changed how the body and its microbes handled the later arsenic assault, and that the changes ran in opposite directions in males and females.

In female pups with the early-life exposure history, the adolescent high dose promoted gut microbial diversity and strengthened the network of interactions among bacterial species, indicating a more interconnected and, in ecological terms, more complex community. At the molecular level, the researchers measured the abundance of arsenic biotransformation genes using a high-throughput quantitative PCR chip that targeted eighty genes involved in arsenic reduction, oxidation, methylation, and transport. In females, genes responsible for reducing arsenate, the pentavalent and generally more toxic form of arsenic, into arsenite were downregulated. Because arsenite is more readily taken up by cells, dampening this reduction pathway coincided with a meaningful outcome: less arsenic accumulated in the females’ kidneys. In other words, the microbial community sculpted by early exposure appeared to blunt the internal dose of the toxin in females, potentially softening the blow of later-life contamination.

Male pups responded in nearly mirror-image fashion. Their gut microbial diversity and network interactions declined under the combined exposure, and instead of retaining arsenic, their bodies excreted more of it in feces, which corresponded with reduced arsenic bioaccumulation in the liver. On the surface, more fecal excretion might sound protective, and for the liver it plausibly was. But the accompanying loss of microbial diversity and the weakening of interaction networks hint at a community under strain, and the study’s authors emphasize that the divergent arsenic metabolic profiles of males and females represent genuinely different biological strategies rather than simply better or worse outcomes. The sex-specific nature of these responses is consistent with a growing body of literature showing that the gut microbiome is shaped by sex hormones and that males and females metabolize xenobiotics differently, but few studies have traced those differences back to exposures occurring before birth.

The technical apparatus behind these conclusions was considerable. The team used inductively coupled plasma mass spectrometry to quantify total arsenic in blood, liver, kidney, and fecal samples, and paired high-performance liquid chromatography with the same detector to separate and measure individual arsenic species, including inorganic arsenate and arsenite and the methylated metabolites monomethylarsonic acid and dimethylarsinic acid. Speciation matters because the toxicity and mobility of arsenic depend entirely on its chemical form, and the gut microbiome is a major site of arsenic methylation and reduction. The researchers also examined histopathology of the ileum and measured the expression of pro-inflammatory cytokines such as IL-8, IL-1 beta, and TNF-alpha, along with transport-related proteins including NaPi-IIb, OATP2B1, and MRP4, which govern how arsenic and its metabolites move across the intestinal barrier. Ecological network analyses of the sequencing data mapped which bacterial groups tended to co-occur or exclude one another, revealing that the architecture of the microbial community, not just its composition, shifted with exposure history and sex.

What emerges from the full dataset is a picture of arsenic as a developmental programming agent whose effects ripple through a biological network spanning metabolism, immunity, and microbial ecology. The authors frame their work as highlighting both the short-term and long-term impacts of arsenic exposure on gut microbiome stability and arsenic metabolic characteristics under different exposure conditions, offering what they call novel insights into the developmental toxicity of early-life exposure. The practical implications are hard to ignore. If the timing of exposure during gestation determines whether offspring grow slower or faster, and if early-life exposure determines whether a later arsenic burden lands in the kidneys or the liver, then risk assessments built on steady-state exposure assumptions may systematically misjudge the hazard, particularly for girls and boys whose responses diverge from the very start.

The study also carries a broader message for microbiome science. The gut microbiome is increasingly recognized as a mediator between environmental chemicals and human health, and this work demonstrates that its mediating role is calibrated by developmental timing and biological sex. For the hundreds of millions of people worldwide whose drinking water exceeds recommended arsenic limits, and for the fetuses and infants exposed in utero and through breast milk, the findings suggest that the microbial consequences of contamination may be set in motion long before symptoms appear, and that protecting the earliest stages of development may be the most effective intervention point. As the researchers and their funders, including the National Natural Science Foundation of China, continue to untangle the mechanisms, the humble gut microbes of laboratory mice have delivered an unmistakable warning: the health effects of arsenic are written differently in males and females, and the writing begins before birth.

Subject of Research: Sex-specific effects of early-life arsenic exposure on body weight, arsenic metabolism, and gut microbiome stability in mice

Article Title: Sex-specific effects of early-life arsenic exposure on body weight, arsenic metabolism, and gut microbiome stability in C57BL/6J mice

Article References: Xiong, S., Jiang, X., Wu, Y., Li, R., Zhao, F., Xiao, P., Yang, Y., Li, Z., Xie, B., Xu, X., Cai, X., Yin, N., & Cui, Y. (2026). Sex-specific effects of early-life arsenic exposure on body weight, arsenic metabolism, and gut microbiome stability in C57BL/6J mice. Microbiome. https://doi.org/10.1186/s40168-026-02535-1

Image Credits: AI Generated

DOI: 10.1186/s40168-026-02535-1

Keywords: arsenic exposure, gut microbiome, developmental toxicity, C57BL/6J mice, sex differences, arsenic metabolism, microbial diversity, prenatal exposure, environmental toxicology, arsenic biotransformation genes, body weight, kidney bioaccumulation

The numbers themselves are striking. The average blood arsenic concentration across the cohort was 41.86 micrograms per litre, and the average blood lead level was 369.19 micrograms per litre, equivalent to roughly 36.9 micrograms per decilitre. To put that in context, the World Health Organization considers permissible blood arsenic levels to be around 10 micrograms per decilitre and blood lead levels around 5 micrograms per decilitre. In this study population, 87.3 percent of participants exceeded the WHO public-health action threshold of 50 micrograms per litre for lead, 30.4 percent had blood arsenic above 10 micrograms per litre, and about one in five carried arsenic levels above 70 micrograms per litre, a clinical benchmark suggesting significant toxicological concern. The researchers emphasize that these are not isolated hotspots but population-wide exposures spanning rural and semi-urban communities in thirteen districts.

The fieldwork, carried out between June 2023 and January 2025, covered Arwal, Begusarai, Bhojpur, Buxar, Darbhanga, Jehanabad, Khagaria, Munger, Nalanda, Patna, Samastipur, Saran and Vaishali. Participants were recruited through multistage cluster random sampling and ranged in age from twenty to sixty years, with a mean age of just under 46. Adults with known haematological disorders, chronic kidney or liver disease, cancer, recent acute illness or recent blood transfusions were excluded, as were pregnant and breastfeeding women, to ensure that the measured blood abnormalities could be more confidently attributed to environmental exposures rather than pre-existing medical conditions. Written informed consent was obtained from every participant under a protocol approved by the ethics committee of ICMR-Rajendra Memorial Research Institute of Medical Sciences in Patna.

On the laboratory side, the team used graphite furnace atomic absorption spectrometry on a PerkinElmer PinAAcle 900T instrument to quantify total arsenic and lead in digested blood samples, following a nitric and perchloric acid digestion protocol derived from National Institute for Occupational Safety and Health methods. Calibration curves maintained a correlation coefficient of 0.999, quality-control standards were run after every ten samples, and method detection limits were set at 0.09 micrograms per litre for arsenic and 0.08 micrograms per litre for lead. Haematological parameters, including red blood cells, white blood cells, haemoglobin and platelets, were measured within twenty-four hours of collection using a three-part differential automated analyzer. The analytical rigour matters because attributing population health effects to environmental toxicants demands defensible measurement, and this study meets that standard.

The haematological findings are where the study becomes genuinely alarming. Among the 1,279 adults examined, 42.7 percent had red blood cell counts below the normal threshold, 30.3 percent were anaemic with haemoglobin below 12.1 grams per decilitre, 20.9 percent showed leukopenia, meaning abnormally low white blood cell counts, and 41.8 percent had thrombocytopenia, a platelet count below 150,000 per microlitre. These are not marginal deviations at the edge of clinical reference ranges; they affect a substantial fraction of the adult population. The average haemoglobin level in the cohort was 12.71 grams per decilitre, slightly below standard adult reference values, while the average platelet count of 170.25 thousand per microlitre sat uncomfortably close to the lower clinical boundary.

When the researchers applied Pearson correlation analysis to link metal burdens with blood indices, arsenic emerged as the clearer culprit. Blood arsenic concentrations showed a statistically significant negative correlation with white blood cell counts, with a correlation coefficient of minus 0.064 and a p-value of 0.023, and a moderate inverse relationship with platelet counts, with a coefficient of minus 0.108 and a p-value below 0.001. Although these correlations are individually weak to moderate in magnitude, their statistical significance across such a large sample lends biological plausibility to the idea that chronic arsenic exposure acts as both an immunotoxin, suppressing the white cells that form the front line of immune defence, and a haematotoxin, depleting the platelets responsible for clotting. In contrast, blood lead, despite being markedly elevated in absolute terms, showed no statistically significant association with any of the haematological markers examined.

The district-level analysis adds an important geographic dimension to the story. Blood arsenic concentrations were highest in Patna, averaging 181.20 micrograms per litre, followed by Vaishali at 159.93 micrograms per litre and Arwal at 82.12 micrograms per litre, while districts such as Buxar, Khagaria and Samastipur recorded comparatively low levels. For lead, the picture was inverted: Darbhanga topped the table with an average of 895.61 micrograms per litre, followed by Arwal at 665.63 and Samastipur at 580.72, while Vaishali and Saran showed relatively modest lead levels. Geospatial mapping using GPS coordinates overlaid on satellite imagery revealed that the most heavily contaminated sampling sites cluster along the Ganga River basin, consistent with the well-documented geology of arsenic mobilization in the alluvial sediments of the Indo-Gangetic Plain, where natural leaching and tectonic activity release arsenic into shallow aquifers that millions of people draw on for drinking and cooking.

The divergence between arsenic and lead in their haematological signatures is one of the study’s most thought-provoking findings. Lead is a classical haematotoxin, long known to inhibit the enzyme delta-aminolaevulinic acid dehydratase, a critical step in haem biosynthesis, and to produce microcytic, hypochromic anaemia. Its failure to correlate with blood parameters here does not mean it is harmless. The authors point to several possible explanations, including differences in exposure duration, nutritional status, particularly iron intake, individual susceptibility, physiological adaptation, and the inherent limits of a cross-sectional design that captures a single point in time and may miss cumulative or delayed toxic effects. Previous adult biomonitoring studies, including analyses of NHANES data from the United States, have similarly reported inconsistent haematological associations with lead, and the researchers caution that elevated lead remains a serious public-health problem because of its systemic toxicity to the nervous system, kidneys and cardiovascular system regardless of what the complete blood count shows.

The study also raises the question of combined exposures. Because many participants carried elevated levels of both metals simultaneously, the authors note that additive or modifying interactions between arsenic and lead could influence haematopoiesis in ways that single-metal analyses cannot capture, although such interaction effects were not formally tested. They likewise acknowledge that no information on specific exposure routes was collected, so the internal blood burden cannot be attributed with certainty to drinking water alone, and that unmeasured environmental and nutritional factors may contribute to the observed blood abnormalities. What the data do establish, with unusual clarity for the region, is the scale of internal exposure and the strong suggestion that arsenic is measurably compromising immune and haematopoietic function in the general adult population.

The implications for public health policy are direct. The researchers call for routine biomonitoring programmes across affected districts, universal access to tested and safe drinking water, and strengthened regulatory enforcement against the sources of lead, which include unregulated industrial effluents, informal battery recycling, and lead in paints, spices and cosmetics. Earlier work by some of the same team has documented arsenic contamination in breast milk, lead in breastmilk, elevated blood lead among children and pregnant women, and increased cancer risk across the Gangetic Plains, making the new adult data part of a disturbing continuum that spans entire lifetimes. In a densely populated agrarian state where groundwater remains the dominant water source, the study’s message is unambiguous: the toxic metal burden in Bihar is not a future risk but a present physiological reality, visible in the blood of nearly half the adults tested, and it demands coordinated intervention before the haematological warning signs translate into the clinical disease burden that toxicology predicts.

Subject of Research: Blood arsenic and lead exposure and their associations with haematological parameters among adults in the Gangetic Plains of Bihar, India

Article Title: Haematological investigation of arsenic and lead exposure burden in adult human population at the Gangetic Plains of Bihar, India

Article References: Kumar, A., Kumari, V., Kumar, N., Kumar, A., Kumar, S., Kumar, K., Khan, M., Sharma, M., Agarwal, R., Suman, S., Srivastava, A., Ali, M., Kumar, D., Bishwapriya, A., Sharma, A., Singh, M., Rastogi, M. K., & Ghosh, A. K. (2026). Haematological investigation of arsenic and lead exposure burden in adult human population at the Gangetic Plains of Bihar, India. Discover Toxicology, 3(1), Article 13. https://doi.org/10.1007/s44339-026-00058-w

Image Credits: AI Generated

DOI: 10.1007/s44339-026-00058-w

Keywords: arsenic exposure, lead exposure, heavy metal toxicity, Bihar, Gangetic Plains, haematology, biomonitoring, anaemia, thrombocytopenia, groundwater contamination, public health, Discover Toxicology