The problem the team set out to solve is both chemical and practical. Cadmium and lead are persistent environmental pollutants: neither is metabolized into a less toxic form, and both bioaccumulate in tissues and bone, making them a permanent fixture of the human exposure landscape. Blood levels of these metals reflect recent exposure from external sources, which is why blood is the matrix of choice for surveillance programs such as the German Environmental Survey. But the gold standard sampling method, venipuncture, demands medically trained personnel and relatively high logistical costs. In structurally weak regions or occupational settings where repeated monitoring is needed, those requirements can make large-scale studies impractical or impossible.

Microsampling has long promised a way around this. Dried blood spots, the technique used in newborn screening for decades, involve blotting a drop of capillary blood onto filter paper. The sample dries, can be stored at ambient temperature, and can be collected by non-medical personnel or even by participants themselves. Studies have repeatedly shown high participant acceptability for such methods. But dried blood spots carry two well-documented flaws when it comes to trace metals. First, the filter paper itself can contain background levels of lead and cadmium so high that they exceed the blood levels of non-exposed people, rendering quantification impossible in some earlier studies. Second, the volume of blood absorbed by the paper depends on hematocrit, the proportion of red blood cells in the blood, which varies between individuals and distorts the apparent concentration.

VAMS was designed to overcome the hematocrit problem. The device consists of a hydrophilic polymer tip mounted on a plastic handle. When the tip briefly touches a drop of blood, it wicks up a fixed volume, roughly 24 microliters in the devices used in this study, regardless of the blood’s viscosity or cell content. Until recently, VAMS was mainly the province of pharmaceutical scientists monitoring drug molecules, peptides, and proteins, and of forensic and anti-doping laboratories. Only a handful of studies had applied it to trace element analysis in human blood, including work on prosthesis-related metals, mercury, and lead, and one recent study that attempted simultaneous monitoring of a broader panel of elements under field conditions. Relatively high limits of quantification remained a persistent obstacle.

The Munich team’s study design was deliberately rigorous. They recruited occupationally non-exposed adults at the university hospital and collected paired samples from each participant: about seven milliliters of venous blood drawn by needle, and three separate capillary samples taken by fingertip prick onto VAMS tips, with a fourth tip left empty to measure background contamination. Sixty participants provided samples using VAMS devices straight from the manufacturer. A further twenty-seven participants were sampled with devices that had been pre-cleaned in an ultrasonic bath of 0.5 percent nitric acid at 60 degrees Celsius for 45 minutes, then rinsed in ultrapure water, in an effort to strip out the metals lurking in the polymer itself. All samples were extracted or diluted in nitric acid and analyzed by triple quadrupole ICP-MS, with terbium as an internal standard and helium collision gas to suppress polyatomic interferences.

The background contamination they found was striking. In untreated devices, blank levels equivalent to as much as 373 micrograms per liter of lead were observed, wildly variable and batch-dependent, against participant blood lead levels that ranged from just 4.57 to 49.77 micrograms per liter. For cadmium, the situation was different: background levels were low, around 0.07 micrograms per liter, and pre-cleaning barely changed them. But for lead, the acid wash was transformative. Pre-cleaning reduced the mean lead background by more than 90 percent, from 3.61 to 0.35 micrograms per liter, and cut the variance of the blanks by more than 85 percent. That collapse in uncertainty drove the limit of quantification for lead down from 15.3 to 2.10 micrograms per liter, low enough to detect lead in people with ordinary, low-level environmental exposure.

How well did the fingertip samples match the venous gold standard? For lead, remarkably well. The Spearman correlation between venous and pre-cleaned VAMS results was 0.98, and the Passing-Bablok regression line sat almost exactly on the identity line, meaning the two methods agreed nearly perfectly across the measured range. For cadmium, the correlation improved from 0.84 with untreated devices to 0.91 with pre-cleaned ones, though the regression slope suggested VAMS slightly overestimates cadmium, likely a residue of the background problem. Recovery, the ratio of the VAMS result to the venous result, averaged 117.2 percent for cadmium and 104.6 percent for lead with pre-cleaned devices, and more than 90 percent of lead samples fell within the accepted 70 to 130 percent recovery window. Difference plots showed no concentration-dependent bias, and the average deviation was tiny: 0.04 micrograms per liter for cadmium and 0.31 for lead.

The team also tackled a question that matters enormously for field deployment: can these tiny dried samples survive real-world logistics? Samples in the study were stored at room temperature in aluminum-coated mylar bags for between 14 and 51 days before analysis. A linear model testing whether recovery declined with storage time found no statistically significant relationship for either metal, suggesting that VAMS samples for cadmium and lead remain stable for at least seven weeks at ambient conditions. That is a decisive advantage over liquid blood, which requires freezing, and it opens the door to mailing samples from remote collection sites to central laboratories. The researchers even replaced the commercial clamshell holders with custom 3D-printed polylactide versions, hinting at how cheap and adaptable the workflow could become.

None of this means the method is foolproof, and the authors are candid about its limits. Because the study population was largely unexposed, most cadmium values fell below the VAMS limit of quantification, inflating uncertainty at the low end. A single unnoticed contamination event, a tip touching a surface, a stray dust particle, can wreck a measurement, which is why the protocol demands obsessive hygiene: washed hands, air-dried disinfectant, the first drop of blood wiped away, and the tip only lightly touching the blood drop. The researchers recommend collecting at least three samples per person so that outliers can be identified, and they applied a statistical rule excluding any replicate whose relative standard deviation exceeded 30 percent. Because an extracted VAMS tip cannot be re-analyzed, this triplicate strategy is the only safety net available.

Even with those caveats, the implications are considerable. In populations with genuine exposure, people living near smelters, recycling operations, or contaminated water supplies, blood levels of both metals would sit well above the quantification limits, and the background problem that dominated this study of low-exposed volunteers would fade into irrelevance. Pre-cleaning the devices is simple, cheap, and reproducible, and the authors argue it should become standard practice, along with batch testing of blanks before any field campaign. If those precautions are followed, a finger prick, a plastic tip, and a sealed envelope could replace the needle and the cold chain for surveillance of two of the world’s most stubborn poisons, bringing toxic metal monitoring within reach of communities that have never had it.

Subject of Research: Volumetric absorptive microsampling for blood cadmium and lead biomonitoring

Article Title: Application of volumetric absorptive microsampling (VAMS) for the simultaneous determination of cadmium and lead in blood

Article References: Gutknecht, C., Burianova, A., Bose-O’Reilly, S., & Rakete, S. (2026). Application of volumetric absorptive microsampling (VAMS) for the simultaneous determination of cadmium and lead in blood. Environmental Monitoring and Assessment, 198(9), Article 1018. https://doi.org/10.1007/s10661-026-15796-y

Image Credits: AI Generated

DOI: 10.1007/s10661-026-15796-y

Keywords: volumetric absorptive microsampling, VAMS, cadmium, lead, human biomonitoring, ICP-MS, microsampling, blood analysis, toxic metals, dried blood spots, background correction, environmental health

The research drew on residual blood samples collected during the 2019 endline survey of the FAARM trial, a cluster-randomized study conducted in rural Bangladesh. In total, 719 participants—433 women and 286 children—were included in the investigation. The team, led by Nicholas N. A. Kyei of the Institute of Public Health at Charité – Universitätsmedizin Berlin together with colleagues at Heidelberg University, the Potsdam Institute for Climate Impact Research, and the Institute of Food Chemistry at Universität Münster, analyzed 712 whole blood and 578 serum samples using ultra-high-performance liquid chromatography coupled to tandem mass spectrometry, or UHPLC-MS/MS. This technique can detect and quantify multiple fungal toxins and their metabolites at vanishingly low concentrations, making it the gold standard for human biomonitoring of mycotoxins.

The starkest result concerned ochratoxin A, a nephrotoxic and possibly carcinogenic mycotoxin produced by Aspergillus and Penicillium fungi that frequently contaminates cereals, spices, and dried fruit. OTA was detected in 100 percent of whole blood samples, and its lesser-known isomer, 2′R-ochratoxin A, appeared in 98 percent. Citrinin, a toxin produced by the same fungi and known to damage the kidneys, was found in 91 percent of samples, while Enniatin B, an emerging mycotoxin with antimicrobial and cytotoxic properties, was present in 92 percent. Beauvericin, another emerging toxin, was detected in 6 percent of samples. The sheer ubiquity of these compounds in human blood underscores how difficult it is to avoid mycotoxin exposure where contaminated staple foods form the daily diet.

Perhaps the most consequential finding involved aflatoxin B1, one of the most potent liver carcinogens known to science. Because AFB1 itself is rapidly metabolized, researchers instead measured AFB1-lysine adducts—molecules formed when the toxin’s reactive metabolite binds covalently to the blood protein albumin. Serum samples were enzymatically digested and cleaned up by solid-phase extraction before analysis. The adduct, a biomarker of chronic exposure over the preceding two to three months, was detected in nearly one-quarter of the women and 4 percent of the children with serum samples. Chronic aflatoxin exposure is linked to liver cancer, immune suppression, and child growth impairment, so its presence in a substantial fraction of reproductive-age women is a serious public health signal.

To translate blood concentrations into estimates of actual intake, the team calculated the probable daily intake, or PDI, for the most frequently detected toxins using toxicokinetic-based approaches. The results were alarming. The PDI of ochratoxin A exceeded health-based guidance values in 80 percent of the women and a striking 99 percent of the children. Citrinin intake was of concern for 12 percent of women and 27 percent of children. Children, with their lower body weight and developing organs, emerged as the most vulnerable group, absorbing comparable toxin burdens through smaller bodies and facing proportionally higher risks.

The study’s co-exposure findings add another layer of concern. Toxicology has traditionally assessed chemicals one at a time, yet mycotoxins frequently co-occur on the same food items because the fungi that produce them thrive under similar conditions of humidity, poor storage, and inadequate drying. OTA and citrinin, for instance, are often produced together by the same fungal species, and their combined kidney toxicity may be greater than either alone. With every participant carrying at least two mycotoxins and most carrying three or more, the realistic exposure scenario in rural Bangladesh is a complex toxicological cocktail whose interactions remain poorly understood.

Why is exposure so pervasive? In rural Bangladesh, maize, rice, wheat, and groundnuts are dietary staples, and these crops are highly susceptible to fungal contamination in the country’s hot, humid climate. Smallholder households often lack access to proper drying facilities, hermetic storage, or the means to sort and discard moldy grain. Food safety regulations, where they exist, are difficult to enforce in informal markets. As a result, mycotoxins enter the food supply at the farm level and travel directly to the family plate, with no practical means of avoidance for the households most affected.

The health implications extend beyond acute toxicity. Ochratoxin A is associated with chronic kidney disease and has been classified as possibly carcinogenic to humans. Aflatoxin B1 is a Group 1 human carcinogen that synergizes with hepatitis B infection to multiply liver cancer risk, a particularly worrying combination in regions where hepatitis B remains prevalent. Emerging toxins like enniatin B and beauvericin are only beginning to be characterized, and their long-term effects at chronic low doses are unknown. For children, chronic mycotoxin exposure has been linked in previous research to growth faltering, immune dysfunction, and reduced vaccine response—burdens that compound the already heavy challenges of malnutrition and infectious disease.

The authors emphasize that their findings demonstrate widespread co-exposure to multiple mycotoxins, with OTA, citrinin, and aflatoxin B1 posing notable risks, and they call for urgent, targeted interventions to protect vulnerable populations. Such interventions could include promoting improved post-harvest handling and drying practices, introducing hermetic storage bags that block fungal growth, supporting biocontrol agents that competitively exclude toxigenic fungi in the field, and strengthening food monitoring systems. Because blood biomonitoring captures actual internal exposure rather than estimated dietary intake, the approach used here could serve as a model for other low- and middle-income countries where mycotoxin contamination is suspected but poorly quantified.

The study also highlights the value of repurposing existing trial infrastructure for environmental health surveillance. By analyzing residual samples from the FAARM trial, the researchers obtained population-scale exposure data at a fraction of the cost of a dedicated biomonitoring campaign. As climate change expands the geographic range of toxigenic fungi and staple food systems come under increasing stress, the silent burden of mycotoxins documented in rural Bangladesh is likely a warning of what many other communities face. Making the invisible visible, this study suggests, is the first step toward reducing a health risk that has been simmering in the blood of millions for generations.

Subject of Research: Chronic blood-borne exposure to the mycotoxins aflatoxin B1, ochratoxin A, and citrinin among women and children in rural Bangladesh

Article Title: Chronic exposure to aflatoxin B1, ochratoxin A, and citrinin in women and children and associated health risk characterization: blood biomonitoring evidence from rural Bangladesh

Article References: Kyei, N. N. A., Cramer, B., Humpf, H.-U., Kuhn, M., Sobhan, S., Veerkamp, J., & Gabrysch, S. (2026). Chronic exposure to aflatoxin B1, ochratoxin A, and citrinin in women and children and associated health risk characterization: blood biomonitoring evidence from rural Bangladesh. Environmental Health, 25(1), Article 75. https://doi.org/10.1186/s12940-026-01330-7

Image Credits: AI Generated

DOI: 10.1186/s12940-026-01330-7

Keywords: mycotoxins, aflatoxin B1, ochratoxin A, citrinin, biomonitoring, Bangladesh, blood analysis, risk characterization, food safety, public health, children's health, UHPLC-MS/MS