Unexpected Chemicals Found in Human Milk Raise New Questions About Infant Exposure

• The study revealed chemicals that had never been reported in human milk before — Among the newly identified substances were antimicrobial preservatives, which appear in soaps, disinfectants, and personal care products. Plastic-related antioxidant additives also showed up, reflecting exposure from food packaging and manufactured materials. For parents, this confirms that everyday products leave biological traces in breast milk, even without obvious overuse.

• Agricultural and household chemicals appeared alongside personal-care residues — The researchers also detected propanil, an agricultural herbicide, and chloroxylenol, an antimicrobial common in household disinfectants. None of these compounds had been previously documented in human milk.

• Medication byproducts offered a real-world snapshot of treatment history — In samples from South Africa, scientists identified a breakdown product of efavirenz, a medication once widely used to treat HIV. When chemicals enter your body, they don’t necessarily stay in their original form. Your liver and other organs chemically modify them into metabolites — breakdown products that can be more or less toxic than the parent compound.

This is why researchers now track both the original chemicals and their transformed versions. According to study co-author Stéphane Bayen, the presence of the HIV drug breakdown product indicated maternal use during or before the sample years, before treatment guidelines changed after 2019. This shows how past medical decisions remain visible in biological samples years later.

Bayen described the results as evidence that people experience a “complex cocktail of chemical residues,” shaped by diet, environment, and lifestyle. This matters because chemicals rarely act alone. Two chemicals that seem safe individually might amplify each other’s effects when combined — or create entirely new effects. Regulatory testing evaluates one chemical at a time, but your baby receives them all at once.

• Some chemical levels correlated with measurable infant outcomes — Concentrations of certain chemicals, including bisphenol A and bisphenol AF, aligned with altered growth patterns among South African infants. Jonathan Chevrier, an associate professor of epidemiology involved in the work, stressed that this was the first study of its kind and that replication remains necessary before drawing firm conclusions. Still, this link explains why scientists track growth signals so closely during infancy.

• Breast milk remains the gold standard for infant nutrition — Bayen stated that the detected substances appeared at low concentrations and that the health effects of many remain unknown. Establishing baseline data allows regulators and scientists to expand testing targets beyond the usual suspects.

That creates a practical pathway for reducing exposure over time instead of guessing where risks originate. Once you understand the exposure pathways — how these chemicals travel from products to your bloodstream to your milk — the leverage points for intervention become obvious. You can’t control industrial contamination of the entire food supply, but you can control whether you microwave leftovers in plastic or store them in glass.

• Bisphenols in breast milk linked to measurable changes in infant growth — A study published in Environmental Research examined bisphenols — plastic-related chemicals that disrupt hormones — in breast milk from South Africa and Canada.³ Levels of BPA, BPS, and BPAF were highest in rural South Africa and lowest in Montreal, where only BPS was detected.

Microwaving food in plastic containers and maternal diet strongly influenced exposure. Among South African infants, BPAF aligned with greater body length and head circumference, while higher BPA aligned with smaller head size.

This contradictory pattern reveals a problem with chemical substitution: manufacturers replace BPA with structurally similar cousins (BPS, BPAF), assuming safety, but these “replacements” interact with the body’s hormone receptors in entirely different ways. Same chemical family, opposite biological effects.

• Testing revealed chlorinated chemicals not previously found in human milk — Research published in Exposome used a broad scanning method rather than a preset chemical list.⁴ This approach identified six chlorinated compounds, including disinfectant antimicrobials, pesticide-related chemicals, a UV filter, and a breakdown product of an HIV medication.

Several of these substances had never been reported in human milk before. The findings show that standard testing overlooks meaningful exposures from cleaning products, agriculture, and medical treatments combined.

• Plastic substitutes appeared alongside the chemicals they replaced — A Journal of Exposure Science & Environmental Epidemiology study looked beyond BPA and searched for structurally similar replacements.⁵

Researchers identified 11 additional compounds, including chemicals used in thermal receipt paper, ultraviolet filters, and synthetic antioxidants. Two plastic stabilizers were detected in human milk for the first time. This demonstrates that removing one known chemical often results in exposure to newer alternatives rather than true reduction.

• Parabens showed up in multiple processed forms, not just their original state — A Chemosphere study focused on parabens, preservatives common in cosmetics and personal care products.⁶ Scientists identified common parabens, newly recognized parabens, and sulfated forms that show how the body chemically modifies these compounds.

Some parabens appeared only in South African samples. The same analysis detected phthalates, PFAS, and even a tire-related chemical, illustrating how environmental contamination reaches breast milk through indirect and unexpected routes.

• Country-specific patterns revealed chemical substitution rather than elimination — An Environmental Pollution study measured nine bisphenols using a sensitive extraction method.⁷ South African samples showed higher BPA levels, mostly in processed form, while Canadian samples showed a shift away from BPA toward BPS. BPAF appeared only in South Africa. These findings show that regulatory changes often swap one chemical for another, leaving overall exposure intact rather than reduced.

1. Keep breastfeeding as the nutritional foundation — If you’re breastfeeding, staying the course supports your baby’s immune defenses, gut development, and brain growth, while supplying antibodies, enzymes, and hormones that help guide healthy metabolism.

The researchers behind the breast milk findings stated clearly that breast milk remains ideal for infants because it delivers nutrition and immune protection no substitute can match. Lowering environmental exposure strengthens these benefits by reducing what transfers alongside those protective compounds rather than replacing breastfeeding itself.

2. Filter your drinking water — Drinking water and cooking water contribute to ongoing chemical intake, including residues from pesticides, plastics, and disinfectants. Install a high-quality water filtration system to intercept contaminants before they enter every glass of water you drink, every meal you cook, and every bottle you prepare. This single step lowers cumulative intake without changing routines.

3. Simplify personal care and household products — Many of the unexpected compounds identified in breast milk trace back to soaps, disinfectants, and cosmetic products. Reducing the number of products you use each day lowers the number of preservatives and antimicrobial agents absorbed through your skin.

Fewer products create fewer exposure pathways. Choosing natural personal care products and cleaning agents, or making your own at home, also reduces your exposure to toxic chemicals. Specific swaps that matter:

4. Limit plastic contact with food and beverages — Plastic-related additives detected in breast milk originate largely from food packaging and storage materials. Switch to glass, stainless steel, or ceramic containers to eliminate contact with plastic stabilizers and antioxidants — especially when heating food, since heat dramatically accelerates chemical migration into whatever you’re eating or drinking. Prioritize these changes in order of impact:

5. Use my homemade formula recipe if breastfeeding is not possible — Some parents can’t breastfeed, and that reality deserves a practical solution. In those cases, my homemade formula recipe avoids industrial seed oils and unnecessary additives common in commercial formulas. This option allows greater control over ingredients and reduces exposure to avoidable contaminants.

Below is my preferred dairy-based formula, which will make 36 ounces of milk. If you need to make large batches to last several days, you can do so, but make sure to freeze the finished product. For children who are unable to tolerate milk proteins, I recommend trying my hypoallergenic milk formula instead.