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Human Milk: Still the Best Choice

Rachel Mosteller
Kingwood TX USA
From: NEW BEGINNINGS, Vol. 21 No. 5, September-October 2004, p. 164

Many women choose to breastfeed because of the many studies demonstrating the wonderful nutritional and immunological properties of human milk. So, when stories in the media focus on environmental chemicals found in human milk, it can be disconcerting to the new mother. It's easy to worry and wonder, "Am I actually harming my baby by breastfeeding?"

The short answer is, "No." Human milk is still the right food for babies. All of the research on environmental chemicals in human milk indicates that women should continue to breastfeed.

The very studies that show breastfed babies are healthier have been done in the post-industrial age. The human milk used in the research invariably contained chemicals that came into the environment from people's manufacturing and industrial processes.

It is no surprise that the environment contains chemicals, pesticides, and waste products. Even women who live in geographically isolated regions are exposed to chemicals in the environment. Throughout her lifetime, a woman's body will come in contact with a variety of substances, which are absorbed through her lungs, skin, and digestive track. By the time a baby is born, he or she has already been exposed to a variety of chemicals during pregnancy.

Researchers test mother's milk in order to find out the level and types of pollutants in our bodies. The easiest bio-monitoring (testing humans for pollutants) tests are done using human milk. Urine, blood, and fat tissues can also be tested, but samples can be harder to acquire-and a large sample may be required. Some chemicals don't show up in blood samples, only in tissue samples containing fat. Testing human milk means that the mother can pump it herself, and volunteers are not subjected to needle pricks or invasive procedures to remove fat tissues.

Bio-monitoring of human milk provides an easy way to collect data about which chemicals are retained in body tissues. Researcher Kim Hooper states in his article, "Levels of chemicals in humans (body burdens) are useful indicators of environmental quality and community health." Like other researchers, Hooper says that the bio-monitoring of human milk should not be used to discourage breastfeeding, stating that, "Body-burden monitoring using breast milk should include educational programs that encourage breastfeeding" (Hooper 2002).

Sandra Steingraber, PhD, ecologist, and author of the book Having Faith: An Ecologist's Journey to Motherhood, explains that toxins (including heavy metals such as mercury and lead) and other chemicals (such as flame retardants) bind to milk proteins and become trapped inside the milk fat, which is then carried by the liquid fraction of milk "like so many bath-oil beads."

Humans store environmental contaminants in their fat tissues over their lifetime, and at least 60 percent of the fat in milk-globules is drawn from reserves scattered throughout the mother's body. Hence, human milk carries with it the chemicals the mother has been exposed to and stored her whole life. It is also, therefore, one of the easiest tissue samples to use for monitoring the "body burden" of chemicals for an average adult. Particularly worrisome are the persistent organic pollutants (POPs) including DDT, PCBs, and dioxins, which remain in the environment for years.

The Environmental Working Group's Study of Flame Retardants in Human Milk

The Environmental Working Group (EWG) tested the milk of 20 first-time mothers from all over the United States, and found that every mother showed unexpectedly high levels of bromine-based flame retardants in their milk. Flame retardants are neurotoxic chemicals (chemicals that are poisonous to nerve tissue) used in hundreds of industrial, automotive, and household products, from bedding to computers, carpets to foam padding, wastewater pipes to electrical connectors. The study confirmed that American women have far higher levels of flame retardants in their body tissues than women in Europe (Lunder 2003).

There are many types of flame retardants with varying levels of toxicity. The most potentially dangerous type still being manufactured today is a group of brominated fire retardants called polybrominated diphenyl ethers, or PBDEs. PBDEs are the chemical cousin to PCBs and, like PCBs, they are persistent in the environment and bioaccumulative, meaning they build up in people's bodies over a lifetime. While PCBs have been banned in the United States, the United States Environmental Protection Agency has set no safety standards on the manufacture, use, or disposal of flame retardants. Earlier studies that showed PBDEs rapidly accumulating in the human milk of Swedish mothers prompted a ban on their use in Sweden, Germany, and Netherlands in the mid-1980s and early 1990s. Since the ban, the level of fire retardants in Swedish mothers' milk has declined. Since the beginning of 2004, the European Union has also banned the use of PBDEs. It is therefore likely that a similar ban in the US would have a similar effect.

What the Studies Show and What Remains Unknown

While the EWG found high levels of PBDEs in American mothers' milk, the research on what the effects are on babies remains unclear. While low exposures of PBDEs in laboratory animals have been linked with thyroid hormone disruption, permanent learning and memory impairment, behavioral changes, hearing deficits, delayed puberty onset, decreased sperm count, fetal malformations, and, possibly, cancer, it is difficult and unpredictable to transfer those findings to humans.

As Cheston Berlin, MD, professor of pediatrics and pharmacology at Hershey Medical Center in Pennsylvania, says:

Of course, there is concern for PBDEs, just as there's concern over the 500 different compounds in tobacco smoke and thousands of other chemicals in the environment. But I don't know of any documented problems with bromated flame retardants in terms of exposure to an infant. (Kircheimer 2003)

It's important to note that many studies of laboratory animals and humans show that many of the problems associated with exposure to environmental contaminants occur in utero and not during breastfeeding or after. Sonya Lunder, an environmental analyst for the Environmental Working Group, writes:

Several long-term studies have followed groups of babies exposed to PCBs (polychlorinated biphenyls) in utero and found that the breastfed babies appear to be less impacted by the chemical exposures than their formula-fed counterparts. One study of Michigan [USA] babies found significant improvements in babies breastfed for at least six weeks. The researchers concluded that PCB exposures in the womb were responsible for the neurological impacts, and that breastfed infants showed far fewer effects of PCB exposure. (Lunder 2003)

Still, according to some Dutch studies, mothers whose milk is more contaminated have children with more mental and psychomotor deficits, although less than there are in formula-fed infants.

In reading and evaluating any study, it is important to consider who conducted the study and their methodology. For example, recent Dutch research on toxins in human milk, specifically PCBs and dioxin, which used pooled milk and were conducted by labs connected to the formula industry, linked high levels of chemicals in human milk with some mothers' inability to even produce milk. The US Natural Resources Defense Council, in commenting on dioxin in human milk, states the following:

A group of women may all donate samples that are then combined into one sample for analysis. This means that individual levels, and the variability (range) of dioxin levels, may not be known. Not knowing the range can be problematic because outliers (extremely high or low values) can indicate unique exposure scenarios.

What Mothers Need to Know

Environmental pollution is a reason to get rid of toxins from the environment, not to get rid of breastfeeding. As stated in "Towards Healthy Environments for Children," a FAQ (frequently asked questions) sheet published by WABA:

The existence of chemical residues in breastmilk is not a reason for limiting breastfeeding. In fact, it is a reason to breastfeed because breastmilk contains substances that help the child develop a stronger immune system and gives protection against environmental pollutants and pathogens. Breastfeeding can help limit the damage caused by fetal exposure. (WABA 2003)

If mothers are looking to take specific action to reduce the level of chemicals in their body, research shows that not smoking cigarettes and not drinking alcohol helps reduce pollutants in the body. Also, limiting fish intake from waters reported as contaminated and limiting exposure to chemicals, such as solvents in paints and gasoline fumes, can help reduce environmental contaminants.

Mothers do not need to have their milk tested, according to "Towards Healthy Environments for Children."

Individual testing of breastmilk should never be used as a basis for making decisions about breastfeeding, except in the rare case of an emergency short term response to an industrial accident. (WABA 2003)

Breast Is Still Best

No discussion on chemicals in human milk would be complete without looking at the risks of not breastfeeding. Although soy-based and cow's milk-based infant formulas are generally lower in some chemicals, they are hardly contaminant-free. In many areas of the midwestern United States, artificially fed infants are exposed to high doses of weed killers and nitrate fertilizers when powdered formula is mixed with tap water (Steingraber 2001). An artificially fed baby born in those regions will have absorbed 25 percent of his or her lifetime allowable dose of atrazine in his first year (EWG 1999). Most water treatment plants cannot filter these contaminants out. Also, formula tends to be more contaminated with lead than human milk. Human milk is, and always will be, a living, changing fluid that adapts to the needs of the infant.

Unless a mother's exposure to contaminants is extremely high-as in high-level occupational exposures-the benefits of human milk far exceed the risks of low levels of chemicals in human milk (Schrieber 2001). In fact, there is evidence that human milk, with its species-specific optimal nutrition and its anti-inflammatory agents, including antioxidants, helps a child develop a stronger immune system and other potential protection against environmental pollutants and pathogens. In regard to organochlorine compounds (organic compounds containing chlorine), a recent study in Pediatrics states:

Long-term breastfeeding was found to be beneficial to neurodevelopment, potentially counterbalancing the impact of exposure to these chemicals through breast milk. (Ribas-Fito 2003)

Though each person carries some body burden of chemicals, human milk is the perfect food for babies, species specific, and designed for optimal growth and development. It is pollution, not breastfeeding, that needs to be stopped at its source.

Ruth Lawrence, MD, a breastfeeding researcher at the University of Rochester School of Medicine, leads the toxicology committee of the Academy of Breastfeeding Medicine. She states:

I certainly wouldn't suggest for one minute that you shouldn't breastfeed or that the theoretic risk of passing a few more nanograms of this chemical to your baby outweighs the tremendous benefit of breastfeeding. (Kircheimer 2003)


Berlin, Jr, C., Lakind, J., and Selevan, S. Human Milk Monitoring for Environmental Chemicals: Guidance for Future Research. ABM News and Views. 2003.

Crase, B. Pesticides and breastfeeding. LEAVEN 1994; 30(4):37-40.

DeKoning, E.P. and Karmaus, W. PCB exposure in-utero and via breast milk: A review. J Expo Anal Environ Epidemiol 2000; 10:285-93.

Environmental Working Group. Into the Mouths of Babes: Bottle-fed Infants at Risk from Atrazine in Tap Water. 1999.

Gross-Loh, C. Breastfeeding, biomonitoring and the media. Mothering 2004 Jan-Feb; 122.

Hooper, K. and She, J. Lessons from the polybrominated diphenyl ethers (PBDEs): Precautionary principle, primary prevention, and the value of community-based body-burden monitoring using breast milk. Environ Health Perspect 2002; 111:109-14.

Hormann, E. Breastfeeding in a polluted world: The fears, the facts, the solutions. Mothering 2000 May-Jun; 66.

Jacobson, J.L. and Jacobson, S.W. Association of prenatal exposure to an environmental contaminant with intellectual function in childhood. J Toxicol Clin Toxicol 2002; 40(4):467-75.

Lawrence, R. A Review of the Medical Benefits and Contraindications to Breastfeeding in the US. Technical Information Bulletin, National Center for Education in Maternal and Child Health, Oct. 1997.

Lunder, S. and Sharp, R. et al. Study Finds Record High Levels of Toxic Fire Retardants in Breast Milk from American Mothers. Environmental Working Group, 2003.

Mittelstaedt, M, "Flame Retardant In Breast Milk Raises Concern," The Globe and Mail, 7 June 2004.

Ribas-Fito, N. et al. Breastfeeding, exposure to organochlorine compounds, and neurodevelopment in infants. Pediatrics 2003; 111(5):580-85.

Roan, S, "When Breast Milk Talks, People Listen," Los Angeles Times, 6 October 2003.

Schreiber, J. Parents worried about breast milk contamination: What is best for baby? Pediatr Clin of North Am 2001; 48(5):1113-27.

Schreiber, J. "Transport of Organic Chemicals to Breast Milk: Tetrachloroethene Case Study," in Environmental Toxicology and Pharmacology of Human Development, (London: Taylor and Francis, 1997) 95-143.

Steingraber, S. Having Faith: An Ecologist's Journey to Motherhood. New York: Berkley Books, 2001.

For more information:

Living Organic
Adrienne Clarke
Sourcebooks, 2001
Living Organic is the ultimate handbook for those wanting to learn more about living naturally, avoiding toxins and moving towards a healthier lifestyle. In harmony with the choice to breastfeed, this book offers practical advice, helpful hints, and additional resources for living a modern life without the addition of unnecessary chemicals.

Breastfeeding, Breast Milk, and Environmental Contaminants
International Lactation Consultant Association (ILCA), 2003

Healthy Milk, Healthy Baby: Chemical Pollution and Mother's Milk
Natural Resources Defense Council (NRDC), 2001

Towards Healthy Environments for Children: Frequently asked questions about breastfeeding in a contaminated environment.
World Alliance for Breastfeeding Action

Working Together for a Toxic-Free Future
World Alliance for Breastfeeding Action

What You Can Do

It is impossible to reduce exposure to all contaminants. However, for those who would like to reduce contact with chemicals, especially before pregnancy and during pregnancy and lactation, the following suggestions may be helpful.

10 Simple Steps to Help Reduce the Level of Chemicals in Your Body

  • Avoid smoking cigarettes and drinking alcohol. The levels of contaminants have been found to be higher in those who smoke and drink alcoholic beverages.
  • Avoid pesticides and lead-based paints. Be aware when purchasing homes and buildings that have been treated with pesticides for termites and/or older homes that might have lead-based paints.
  • Reduce consumption of animal fats. In general, eat a variety of foods low in animal fats, remove skin and excess fat from meats and poultry. Avoiding high-fat dairy products may reduce the potential burden of fat-soluble contaminants.
  • Increase consumption of grains, fruits, and vegetables. Thoroughly wash and peel fruits and vegetables to help eliminate the hazard of pesticide residues on the skin. When available, eat food grown without fertilizer or pesticide application.
  • Reduce consumption of freshwater fish. Avoid swordfish and shark or freshwater fish from waters reported as contaminated by local health agencies.
  • Limit exposure to common chemicals. Common chemicals include solvents found in paints, non-water based glues, furniture strippers, nail polish, and gasoline fumes.
  • Limit exposure to dry-cleaned garments. Remove the plastic cover of dry-cleaned clothing, and air out the garments in a room with open windows for 12-24 hours.
  • Avoid contact with incinerator products. Try to avoid contact with incinerator discharge (smoke and ash), preserved wood, or produce grown near incinerators.
  • Avoid occupational exposure to chemical contaminants. For those in the workforce, attempt to avoid occupational exposure to chemical contaminants and seek improved workplace chemical safety standards for all employees, especially pregnant and lactating women.
  • Avoid bringing contaminant residue into the home. Encourage other family members to be sensitive to contaminant residue they may inadvertently bring into the home.

Adapted from the LLLI media release, "Breastfeeding Remains Best Choice in a Polluted World." For more information, see the following LLLI Web pages:


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