Trace Heavy Metals in Ghanaian Breast Milk Pose Low Risk to Infants

Breast milk remains the gold standard of infant nutrition, delivering essential nutrients, immunological protection, and bioactive compounds that shape a child’s early development. The World Health Organization recommends exclusive breastfeeding for the first six months of life precisely because of these unmatched benefits for both mother and child. Yet breast milk also carries a little-known double role: it can serve as a transfer pathway for environmental contaminants, including toxic heavy metals, moving from mother to infant during lactation. A new study from Ho, Ghana, has now provided one of the most detailed pictures yet of what lactating mothers in the region carry in their milk, and the headline finding is broadly reassuring—although arsenic remains a chemical worth watching.

Researchers from the University of Health and Allied Sciences and collaborating institutions conducted a cross-sectional biomonitoring study at Ho Teaching Hospital, a tertiary facility serving the Volta Region, between December 2020 and June 2021. Forty-seven lactating mothers practicing exclusive breastfeeding were enrolled after careful screening that excluded mothers with chronic conditions such as diabetes or hypertension, those on long-term medication, mothers with breast infections, and those practicing mixed feeding. Written informed consent was obtained from every participant, with ethical approval from the University of Health and Allied Sciences Research Ethics Committee. Recruitment proved challenging—the study fell short of its target of 50 participants—because breast milk donation for research was unfamiliar in the setting, and the requirement for repeated sampling at three lactation stages increased the burden on volunteers. Nevertheless, the achieved sample represented 94 percent of the target and proved sufficient for exploratory biomonitoring.

What distinguishes this investigation methodologically is its composite sampling strategy. Rather than relying on a single milk sample drawn at one point in lactation, the researchers collected approximately 10 milliliters of colostrum within five days postpartum, transitional milk between days six and fourteen, and mature milk from day fifteen onward. Equal volumes from the three stages were pooled into a 30-milliliter composite sample for each participant. This design matters because contaminant concentrations are known to shift across lactation stages, and many earlier studies that sampled only one stage may have systematically underestimated or overestimated infant exposure. By integrating all three stages, the team produced an estimate of exposure that better reflects the entire exclusive breastfeeding window. Samples were stored at minus 20 degrees Celsius, transported under cold chain, digested with nitric acid and hydrogen peroxide, and analyzed on a Thermo Scientific iCAP 7400 Duo ICP-OES instrument following US EPA Method 2007 principles. Quality assurance included reagent blanks, duplicate analyses, and certified reference material, with recovery rates between 85 and 115 percent and relative standard deviations under 5 percent.

The results revealed generally low concentrations of five target metals: aluminum, arsenic, cadmium, lead, and mercury. Aluminum showed the highest mean concentration, followed by arsenic, mercury, lead, and cadmium. Detection frequencies were high for aluminum, arsenic, and mercury, moderate for lead, and notably low for cadmium, which appeared in only about a third of samples. Mercury displayed the greatest relative variability, with a coefficient of variation approaching 283 percent, hinting at uneven and possibly localized exposure sources among the mothers. When the authors compared their means against historical WHO and International Atomic Energy Agency breast milk biomonitoring data, concentrations of arsenic, cadmium, lead, and mercury all fell below those earlier comparator values, which date back to a joint collaborative study across Guatemala, Hungary, Nigeria, the Philippines, Sweden, and Zaire.

Correlation analysis uncovered a few significant associations. Aluminum and lead concentrations were positively correlated with each other, suggesting they may share a common environmental or dietary pathway. More intriguingly, aluminum showed an inverse relationship with gestational age, and lead did as well, meaning mothers who delivered at earlier gestational stages tended to show higher concentrations of these metals in their milk. Using the Kruskal-Wallis test, the team also found that cadmium concentrations differed significantly according to maternal parity, with multiparous mothers showing distinct distributions. The researchers consider this biologically plausible: cadmium has a prolonged biological half-life and accumulates in maternal tissues over years, so women who have experienced more pregnancies and lived longer with accumulated body burdens may mobilize more of the metal during lactation. No significant associations emerged between the other metals and maternal age, body mass index, or gestational age, echoing findings elsewhere that environmental and behavioral exposure pathways often outweigh individual maternal characteristics.

To translate concentrations into health meaning, the team estimated average daily intakes and hazard quotients for breastfed infants under two scenarios: a typical milk ingestion rate of 0.510 liters per day and an upper scenario of 0.950 liters per day, standardized to an average infant body weight of 4.6 kilograms. The hazard quotient compares estimated daily exposure against a toxicity reference value drawn from agencies such as the US EPA and ATSDR. For every metal with an applicable reference value, all hazard quotients came in below the threshold of 1 under both scenarios, indicating that estimated exposures sit comfortably below levels of toxicological concern. Arsenic produced the highest quotients, at roughly 0.068 under typical intake and 0.127 under upper intake, followed by mercury, then cadmium. No hazard quotient was calculated for lead because no consensus oral reference dose exists for inorganic lead—a regulatory gap the authors handled conservatively by excluding it rather than guessing.

The carcinogenic side of the assessment tells a more nuanced story. The researchers calculated lifetime average daily doses over the 180-day exclusive breastfeeding period, averaged across a 70-year lifespan, and applied cancer slope factors for arsenic, cadmium, and lead. Arsenic again dominated, yielding an estimated carcinogenic risk of about 9.25 times 10 to the minus 7 under typical intake and 1.72 times 10 to the minus 6 under upper intake. The typical-intake estimate sits just below the 10 to the minus 6 benchmark, while the upper-intake estimate lies near the lower end of the 10 to the minus 6 to 10 to the minus 4 risk-management range commonly applied in environmental health practice. Cadmium and lead risks were orders of magnitude lower. Crucially, however, the study measured total arsenic rather than distinguishing its chemical species. Because inorganic arsenic is the principal carcinogenic form and organic arsenic species are far less hazardous, applying an inorganic arsenic slope factor to total arsenic yields a deliberately conservative screening estimate that likely overstates real risk. The authors are explicit that arsenic speciation in future studies would sharpen the picture considerably.

Placed in global context, the findings align with a growing body of evidence from low- and middle-income settings. Recent assessments in northeastern Algeria detected lead, mercury, cadmium, and arsenic in breast milk but reported generally low infant risks, while work in Iran has highlighted substantial population-level variability driven by diet, environmental contamination, and maternal characteristics. Systematic reviews confirm that maternal consumption of fish and seafood influences breast milk concentrations of several metals. Within Ghana itself, breast milk biomonitoring data remain scarce, though earlier work in Obuasi detected mercury among lactating mothers, underscoring why continued surveillance matters in a country with a long history of artisanal gold mining and its associated mercury use. This study’s integrated exposure and risk framework—one of the first of its kind for Ghana—fills a genuine regional data gap.

The public health message is ultimately affirmative. Despite detectable concentrations of toxic metals, every hazard quotient fell below 1, and lifetime carcinogenic risk estimates were generally low, supporting the continued promotion of breastfeeding even in environments with low-level contamination. Breastfeeding’s established protective benefits far outweigh the modeled risks under the exposure assumptions applied. At the same time, the authors emphasize that their findings should not breed complacency. The study’s limitations include a modest sample from a single hospital, reliance on standardized rather than participant-specific milk ingestion rates and infant weights, measurement of total rather than speciated arsenic and mercury, and the absence of quantitative source attribution for maternal exposure. Future research incorporating larger cohorts, arsenic speciation, individualized exposure parameters, and dietary and environmental characterization would enable more precise risk estimates.

For Ghana, the study delivers something the country has lacked: a baseline. Composite breast milk sampling across colostrum, transitional, and mature milk offers an integrated, realistic portrait of what exclusively breastfed infants actually ingest during their most vulnerable developmental window. The finding that cadmium tracks with parity adds a biologically grounded marker for identifying mothers who may carry higher accumulated body burdens, and the aluminum-gestational age link invites further investigation into prenatal exposure dynamics. As environmental pressures intensify across West Africa through mining, industrialization, and changing food systems, systematic breast milk biomonitoring of this kind offers an early-warning instrument—one that protects both the credibility of breastfeeding promotion and the health of the next generation.

Subject of Research: Heavy metal contamination in composite breast milk and health risk assessment for breastfed infants in Ho, Ghana

Article Title: Heavy metal concentrations in composite breast milk and health risk assessment for breastfed infants in Ho, Ghana

Article References: Jonathan, J. W. A., Kabotso, D. E. K., Essumang, D. K., Bentum, J. K., Boamah, I., Nketsiah, J., Gborgblorvor, I. R., Dayie, A. D., & Hayfron, J. (2026). Heavy metal concentrations in composite breast milk and health risk assessment for breastfed infants in Ho, Ghana. Heliyon, 12(15), Article e45425. https://doi.org/10.1016/j.heliyon.2026.e45425

Image Credits: AI Generated

DOI: Not provided

Keywords: breast milk, heavy metals, arsenic, cadmium, lead, mercury, aluminum, infant health risk, biomonitoring, Ghana, breastfeeding, carcinogenic risk