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