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By Melissa Fleur Afshar
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Researchers at McGill University have identified several unexpected chemical contaminants in human milk, finding traces of pesticides, antimicrobials and additives used in plastics and personal‑care products.
The team said the data, drawn from Canadian and South African samples, could help strengthen chemical safety regulations and improve protections for infants and parents.
“It is important to note that these chemicals were detected at low concentrations, and we do not fully understand the health effects of many of them. So, despite these findings, breast milk remains ideal for infants, as it has the nutrients infants need to develop as well as antibodies that protect them against diseases,” Stéphane Bayen, the study's co-author, said in a statement.
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A group of scientists published the results across five papers after analyzing 594 human milk samples collected between 2018 and 2019 in Montreal, Vhembe and Pretoria.
The researchers used a non‑targeted analysis, allowing them to search broadly for unusual chemical residues rather than focusing on individual, pre‑selected substances. This approach enabled them to detect several compounds not previously reported in human milk.
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What Did the Researchers Find?
Among the newly identified chemicals were antimicrobial preservatives 2‑ethylhexyl 4‑hydroxybenzoate and phenyl paraben. These ingredients are commonly added to soaps, disinfectants and personal‑care items. The researchers also found two plastic‑related antioxidant additives—Irganox 1010 and BHT‑COOH—used during manufacturing to package materials.
Additional contaminants included propanil, an agricultural herbicide, and chloroxylenol, an antimicrobial used in disinfectants and household products.
In South African samples, the team also detected 8‑hydroxyefavirenz, a breakdown product of efavirenz, a medication used to treat HIV.
How Were the Chemicals Found?
To identify these substances, the scientists combined different data‑mining strategies with high‑resolution mass spectrometry, a technique capable of pinpointing molecules in complex samples. This method allowed them to detect unexpected or unknown contaminants that may not appear in conventional testing.
The research also identified potential links between certain contaminants and infant health.
The team reported that concentrations of bisphenol A (BPA) and bisphenol AF in breast milk were associated with altered growth among South African infants. While the study did not examine specific health outcomes, the association underlined the need for further investigation into how contaminants present in milk might influence early development.
Is Breastfeeding Still Safe?
The researchers said their findings should not discourage breastfeeding or frighten new parents but instead highlight how environmental exposures can reach infants.
Jonathan Chevrier, an associate professor at McGill added: “This is the first study of this type, and so results need to be replicated before any conclusion can be drawn. Human milk is considered the gold standard for infant nutrition. It is therefore essential to understand everything infants are exposed to during this critical window of susceptibility in development."
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References
Chi, Z. H., Cariou, R., Motteau, S., Le Bizec, B., Dervilly, G., Liu, L., Zheng, J., Tian, L., Chevrier, J., Bornman, R., Obida, M., Goodyer, C. G., Robaire, B., Hales, B. F., & Bayen, S. (2025). Application of non-targeted analysis for the identification of uncommon or unreported chlorinated contaminants in human milk. Exposome, 5(1). https://doi.org/10.1093/exposome/osaf008
Chi, Z. H., Liu, L., Zheng, J., Tian, L., Chevrier, J., Bornman, R., Obida, M., Gates Goodyer, C., Hales, B. F., & Bayen, S. (2025). Investigation of common and unreported parabens alongside other plastic-related contaminants in human milk using non-targeted strategies. Chemosphere, 373. https://doi.org/10.1016/j.chemosphere.2025.144154
Chi, Z. H., Liu, L., Zheng, J., Tian, L., Chevrier, J., Bornman, R., Obida, M., Goodyer, C. G., Hales, B. F., & Bayen, S. (2024). Biomonitoring of bisphenol A (BPA) and bisphenol analogues in human milk from South Africa and Canada using a modified QuEChERS extraction method. Environmental Pollution, 348. https://doi.org/10.1016/j.envpol.2024.123730
Chi, Z. H., Liu, L., Zheng, J., Tian, L., Chevrier, J., Bornman, R., Obida, M., Goodyer, C. G., Hales, B. F., & Bayen, S. (2025). Suspect screening of bisphenol A (BPA) structural analogues and functional alternatives in human milk from Canada and South Africa. Journal of Exposure Science & Environmental Epidemiology, 35(4), 557–566. https://doi.org/10.1038/s41370-025-00782-2
Elsiwi, B., Bayen, S., Chi, Z. H., Goodyer, C. G., Hales, B. F., Robaire, B., Bornman, R., Obida, M., Moodie, E. E. M., & Chevrier, J. (2025). Breast milk bisphenol concentrations in Canada and South Africa and associations with body size among South African infants. Environmental Research, 285, 122452. https://doi.org/10.1016/j.envres.2025.122452
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