A Spanish study found traces of environmental pollution in breast milk

By Dr. Liji Thomas, MDJul 6 2022Reviewed by Benedette Cuffari, M.Sc.

Breastfeeding is important for the health of both the mother and infant. By providing nutrients, immunologic factors, emotional satisfaction, and bonding, breastfeeding is recommended to begin within an hour of birth and continue for a minimum of six months.

Environmental pollution continues to have a significant impact on many aspects of modern life, including breastfeeding. A new Environment International study reveals that breast milk is often contaminated by environmental pollutants, including those that can disrupt the hormonal balance, brain development, and establishment of the gut microbiome in the infant.

Study: Mixture of Environmental Pollutants in Breast Milk from A Spanish Cohort of Nursing Mothers. Image Credit: Art_Photo / Shutterstock.com

Introduction

Breastmilk contains a rich array of nutrients, including lactose, proteins like caseinogen, and fats. Additionally, breast milk contains important bioactive compounds such as secretory immunoglobulin A (sIgA), lactalbumin, lysozyme, growth factors for various tissues including the brain and epidermis, and immunological factors.

Children who were breastfed as infants are more likely to be protected against excess weight gain in later life, have a higher intelligence quotient and have greater capabilities to think and react to stimuli.

Breastfeeding also promotes the development and maturation of the immune system. In fact, breastfed babies have a lower risk of respiratory infection, diarrhea, anemia, and hypertension.

Moreover, breastfeeding is associated with better oral development due to the sucking action. The digestibility of breast milk has also been shown to reduce the incidence of colic.

Breastfeeding is also associated with several benefits for the mother, some of which include a lower incidence of breast, uterus, and ovarian cancers, osteoporosis, cardiovascular disease, and type 2 diabetes. Furthermore, breastfeeding appears to promote a return to a normal body weight after childbirth.

Pollution and breastmilk

The cumulative exposure of women to environmental pollutants, especially persistent organic pollutants (POPs) such as polychlorinated biphenyls (PCBs), dioxins, and furans, as well as toxic metals, has led these chemicals to be identified at varying concentrations within breastmilk. Some of these chemicals disrupt normal endocrine function, which could subsequently affect the normal development of the infant.

The effect of these chemicals on the infant microbiome could also be significant, as it is a crucial component of immunologic maturation. Furthermore, neurotoxicity is a concern in infants consuming contaminated breast milk, as their immature brains are more vulnerable to exposure to such toxins.

Study findings

The current study reports the levels of various pollutants found in breastmilk samples collected from a group of Spanish women. The measured pollutants included various POPs such as dichlorodiphenyltrichloroethane (DDT), dichlorodiphenyldichloroethylene (DDE), hexachlorobenzene (HCB), oxy-chlordane, PCBs, polybrominated diphenyl ethers (PBDEs) congeners, and both per- and poly-fluoroalkyl substances (PFASs).

DDT was found in all samples at a concentration of up to about 900 pg/mL of milk or 2 ng/g of fat. Similar levels have been reported in the breastmilk of mothers residing in other European countries as well. DDE, which is a metabolite of DDT, was found in concentrations of up to 62,000 pg/mL or about 70 ng/g of fat.

HCB was found at levels comparable to DDT at about 300 pg/mL and 11 ng/g fat.

Oxy-chlordane was identified in about 50% of samples at concentrations of up to about 200 pg/mL and 7 ng/g fat. This was lower than recent Norwegian and Swedish figures that reported concentrations of up to 30 ng/g fat, as well as previous findings from a 2002 Spanish study.

Nine of 11 PCB congeners were detected in the samples, with the highest concentration being about 800 pg/mL for PCB-153

Different PBDEs congeners were found at different levels, with BDE-47 found in all samples. Comparatively, BDE-153 was found at a concentration of about 10 pg/mL. Earlier studies showed higher PBDE levels than those which were reported in the current study, which corroborates the declining levels of PCBs over the last several decades.

PFASs were undetectable in all samples, thus indicating a lower level than earlier samples. However, perfluorooctane sulfonate (PFOS), which is a type of PFAS, was found in almost 90% of samples.

Several other pollutants were also identified in the breastmilk samples analyzed in the current study. These included chlorpyrifos, bisphenol A (BPA), tetrabromobisphenol A (TBBPA), and several other toxins.

Chlorpyrifos, for example, was present in up to 40% of samples at concentrations of up to 150 pg/mL and 11 ng/g fat. While these levels compare with those of most other non-European countries, as European levels were not available at the time the study was conducted, they were much lower than those reported in Iran or India, which were over 2,000 pg/mL and about 70 ng/g fat.

Whereas BPA was identified in about 90% of samples at a concentration of about 2 ng/mL, TBBPA was present in half the samples at a concentration of up to 0.02 ng/mL or 13 ng/g fat.

Other toxins like mercury were found in 12% of samples, which is near the limit of detection, whereas methylmercury was invariably absent. In contrast, up to 60% of Italian samples showed the presence of this toxin, and lower levels were found in other countries.

Several metals including aluminum, arsenic, copper, chromium, manganese, and lead, while essential elements, were found in all samples. Moreover, some toxic elements were detectable in up to 15% of samples, including arsenic, chromium, and mercury.

Notably, infant formula also contains environmental pollutants, as does baby food, presumably from the manufacturing chain.

Risk factors

HCB and PCBs were found at higher levels in samples from older women, with other POPs showing the same age-dependent trend that is likely due to cumulative exposure. Conversely, PFOA was found in younger mothers.

POPs including DDT and DDE were present at higher levels in mothers with lower income. This may be due to their varying exposure to such pollutants as compared to those in a wealthier social stratum.

Arsenic, chromium, and manganese levels were all higher in passive smokers, which could be the result of exposure to tobacco smoke.

The body mass index (BMI) of mothers was positively correlated with DDT, DDE, and HCB concentrations, as many of these contaminants accumulate in fat cells. Other chemicals did not show such a correlation, which corroborates previous studies.

Spanish mothers appeared to have higher PCB levels than those of other nationalities. Other sociodemographic factors did not show any correlation, nor did dietary habits or the use of personal care products like creams and makeup.

Infants younger than one month, those between the age of one and six months, as well as those older than nine months of age were found to have been exposed to BPA, PFASs, and PCBs above the tolerable daily or weekly intake. Thus, it is essential to understand how these toxins travel through the infant’s body during early life to set proper tolerability limits.

Implications

The study findings indicate that breastmilk may expose infants to potentially harmful pollutants that can disrupt their development and health.

“This cocktail of toxic substances is not exclusive of breast milk, since chemicals can be also found in infant formulas. Biomonitoring and food monitoring studies are clearly required, not only to control the presence of pollutants in children’s food, but also to raise awareness of competent inspection authorities.”