Mother’s milk is widely considered the safest and purest source of nutrition for infants. But a recent study has raised concern after it found that breastmilk samples collected from 40 lactating mothers in Bihar were ‘highly contaminated’ with uranium. The study, published in the journal Nature, analysed samples collected over nearly three years. Although uranium was detected in all the samples, the researchers said the levels were below the limit considered harmful and would likely have ‘very least impact’ on the health of mothers and their infants.
Study conducted across six districts
The study was carried out between October 2021 and July 2024 in six districts of Bihar: Bhojpur, Samastipur, Begusarai, Khagaria, Katihar and Nalanda. Fourty mothers aged between 17 and 35 took part in the research. Each participant provided a breastmilk sample, which was then tested for uranium content.
The findings showed that every single sample contained uranium. According to the report, “The present study reports 100 per cent of lactating mothers having their breastmilk highly contaminated with uranium.” Researchers said the highest contamination level was found in Katihar district, where uranium concentration in breastmilk reached 5.25 µg/L. Katihar was followed by Samastipur, Nalanda, Khagaria, Begusarai and Bhojpur in decreasing order of exposure.
The study pointed out that while uranium was present in all samples, the measured levels were still below the permissible limits set for drinking water. “However, the reported concentrations are below the permissible limits; hence, there could be at least a significant health threat from uranium exposure,” the study added.
No standard limit for uranium in breastmilk
One of the major observations from the study is the absence of any global or national benchmark for uranium levels in breastmilk. At present, no agency has specified what amount of uranium, if any, is considered safe in human milk. The World Health Organisation (WHO), however, sets a permissible limit of 30 µg/L for uranium in groundwater. This benchmark is often used as a reference point to assess contamination in water sources.
Groundwater identified as possible source
The study examined possible sources of uranium contamination in the region. Researchers found a significant presence of uranium in groundwater samples collected from several districts of Bihar. The highest concentration in groundwater was reported in Supaul district at 82 µg/L, followed by Nalanda at 77 µg/L and Vaishali at 66 µg/L.
According to the report, uranium contamination may be entering the food chain through water used for drinking and irrigation. “The source of uranium contamination in the six studied districts could be drinking water sources or the food source cultivated in the same location,” the study stated.
The researchers also noted that extensive use of groundwater for farming and household use has led to the accumulation of pollutants over time. The study added that untreated industrial waste released into rivers and other water bodies has contributed to the presence of heavy metals in the ecosystem. This contamination can move into the food chain and affect human health. The use of pesticides and chemical fertilisers in agriculture was cited as another major factor polluting soil and water.
Health experts raise concern
While the study reveals that the uranium levels detected in breastmilk samples may not pose an immediate threat, health experts have expressed concern about the long-term effects. Co-author Dr Ashok Sharma from AIIMS told the Times of India that the exact source of uranium contamination remains unclear and that the Geological Survey of India is also investigating the issue.
Dr Sharma suggested that uranium entering the food chain is alarming because it can cause cancer, neurological problems and hinder the growth of children. “It is a very serious concern,” he said.
Possible impact on infants
The study explained that uranium exposure in infants could lead to neurological problems if concentrations rise beyond safe levels. Uranium can interfere with brain development, potentially lowering IQ, affecting learning abilities and increasing the risk of long-term cognitive issues. It may also raise the chances of developing certain cancers later in life.
However, the report emphasised that the overall impact on infants in the current samples is likely to be low. This is because uranium does not accumulate easily in breastmilk. Instead, it tends to collect in the bones and kidneys of the mother due to its attraction to phosphate and carbonate compounds.
The study noted that uranium has a low affinity for milk components such as lipids, proteins and water. It also lacks a specific biological transport mechanism that would allow it to move easily into breastmilk. Additionally, most uranium absorbed by the body is expelled through urine, limiting the amount that could reach an infant through breastfeeding.
Study backed by Indian Research Institutions
The research was conducted at the Mahavir Cancer Sansthan and Research Centre in Patna. It received support from the Indian Council of Medical Research (ICMR) and the National Institute of Pharmaceutical Education and Research (NIPER) in Hajipur, Vaishali. The findings have prompted calls for more extensive testing of groundwater and food sources across Bihar to determine how widespread the contamination might be.
While the study offers some reassurance that health risks remain low for now, experts say the presence of uranium in breastmilk is a warning sign. They believe further investigation and stronger monitoring of water sources are needed to protect mothers and children from long-term exposure.
