Environmental Health Perspectives • VOLUME 110 | NUMBER 6 | June 2002 A 313

Chemical Contaminants in Breast Milk and Their Impacts on Children’s Health: An Overview

Philip J. Landrigan,1 Babasaheb Sonawane,2 Donald Mattison,3 Michael McCally,1 and Anjali Garg1

1Center for Children’s Health and the Environment, Department of Community and Preventive Medicine, Mount Sinai School ofMedicine, New York, New York, USA; 2National Center for Environmental Assessment, U.S. Environmental Protection Agency,Washington, DC, USA; 3March of Dimes Birth Defects Foundation, White Plains, New York, USA

Human milk is, without question, the bestsource of nutrition for infants. Breast milkcontains the optimal balance of fats, carbo-hydrates, and proteins for developingbabies, and it provides a range of benefitsfor growth, immunity, and development(1). Breast milk contains powerful immunefactors that help infants fight infections (2),and it contains growth factors that appear toinfluence brain development and increaseresistance to chronic diseases such asasthma, allergies, and diabetes. Breast-feed-ing builds a powerful bond between amother and her child, and this bondenhances health and well-being across thegenerations. Recognition of the manifoldbenefits of breast milk has led to the adop-tion of breast-feeding policies by numeroushealth and professional organizations (3–9)and stimulated development of the recent“Blueprint for Action on Breastfeeding” bythe U.S. Department of Health and HumanServices (10).

Unfortunately, breast milk is not pristine.Contamination of human milk is widespreadand is the consequence of decades of inade-quately controlled pollution of the environ-ment by toxic chemicals. Polychlorinatedbiphenyls (PCBs), DDT and its metabolites,

dioxins, dibenzofurans, polybrominateddiphenyl ethers (PBDEs), and heavy metalsare among the toxic chemicals most oftenfound in breast milk (11,12). These com-pounds are encountered to varying extentsamong women in industrially developed aswell as in developing nations. Some of thehighest levels of contaminants are seenamong women in agricultural areas of thedeveloping world that are extensively treatedwith pesticides (13) and among women inremote areas, such as the Canadian Inuit,who eat a diet rich in seal, whale, and otherspecies high on the marine food chain thataccumulate heavy burdens of persistentorganic pollutants (POPs) (14).

The finding of toxic chemicals in breastmilk raises a series of important issues forpediatric practice, for the practice of publichealth, and for the environmental healthresearch community.

Lack of data on contaminants. Althoughmuch information has been generated on thetypes of chemicals likely to be found inbreast milk, this database is scattered andincomplete. Data have been collected ononly a limited number of chemicals, fromsmall samples of women in relatively fewgeographic locations (15). Major need exists

for more data on exposure patterns, levels ofcontamination, and trends.

Lack of consistent protocols. No standard-ized methodology has been developed in theUnited States for collecting and analyzingbreast milk samples. This makes it difficult tocompare data from study to study. Althoughmore data are available in other nations,again, standardized protocols do not exist.Methodologic shortcomings of publishedstudies include inconsistent sampling andanalysis protocols, incomplete descriptions ofsampling methods, nonrepresentative sam-pling (in regard to geography, parity, age),limited duration of sampling, small numbersof study participants, and limited numberand types of chemicals analyzed (16).

Lack of toxicokinetic data. Women maybe exposed to lipophilic chemicals from var-ious sources including air, food, water, andoccupational and household environments.

Address correspondence to P. J. Landrigan, Centerfor Children’s Health and the Environment,Department of Community and PreventiveMedicine, Box 1057, 1 Gustave L. Levy Place,Mount Sinai School of Medicine, New York, NY10029 USA. Telephone: (212) 241-4804. Fax:(212) 996-0407. E-mail: phil.landrigan@mssm.edu

This article is an introduction to the Mini-Monograph on “Chemical Contaminants in BreastMilk.” The series of articles in this mini-monographwere developed from ideas developed at the confer-ence on “Chemical Contaminants in Breast Milk:Impacts on Children’s Health.”

The conference, “Chemical Contaminants inBreast Milk: Impacts on Children’s Health,” was sup-ported by the following federal agencies: the U.S.Environmental Protection Agency, the Agency forToxic Substances Disease Registry, the NationalInstitute of Child Health and Human Development,the National Institute of Environmental HealthSciences, and the Centers for Disease Control andPrevention. The conference also received supportfrom the following private foundations: the March ofDimes Birth Defects Foundation, the Pew CharitableTrusts, the Bauman Family Foundation, the ShulskyFoundation, and the Wallace Genetic Foundation.

We thank L. Boni of the Center for Children’sHealth and the Environment for her valuable con-tributions to successfully organizing the conference.

The views expressed in this paper are the opin-ions of the authors and do not represent endorse-ment or policy of their affiliated institutions or theU.S. Environmental Protection Agency.

Received 20 December 2001; accepted 11February 2002.

Human milk is the best source of nutrition for infants. Breast milk contains the optimal balanceof fats, carbohydrates, and proteins for developing babies, and it provides a range of benefits forgrowth, immunity, and development. Unfortunately, breast milk is not pristine. Contaminationof human milk is widespread and is the consequence of decades of inadequately controlled pollu-tion of the environment by toxic chemicals. The finding of toxic chemicals in breast milk raisesimportant issues for pediatric practice, for the practice of public health, and for the environmentalhealth research community. It also illuminates gaps in current knowledge including a) insufficientinformation on the nature and levels of contaminants in breast milk; b) lack of consistent proto-cols for collecting and analyzing breast milk samples; c) lack of toxicokinetic data; and d) lack ofdata on health outcomes that may be produced in infants by exposure to chemicals in breast milk.These gaps in information impede risk assessment and make difficult the formulation of evidence-based health guidance. To address these issues, there is a need for a carefully planned and con-ducted national breast milk monitoring effort in the United States. Additionally, to assess healthoutcomes of toxic exposures via breast milk, it will be necessary to examine children prospectivelyover many years in longitudinal epidemiologic studies that use standardized examination proto-cols that specifically assess breast milk exposures. Finally, current risk assessment methods need tobe expanded to include consideration of the potential risks posed to infants and children by expo-sures to chemical residues in breast milk. Key words: breast milk, breast-feeding, children’s health,chemical contaminants. Environ Health Perspect 110:A313–A315 (2002). [Online 13 May 2002]http://ehpnet1.niehs.nih.gov/docs/2002/110pA313-A315landrigan/abstract.html

CHEMICAL CONTAMINANTS IN BREAST MILKMini-Monograph

edited by PJ Landrigan

Lipophilic chemicals can be stored and accu-mulated over time in body fat and can thenbe mobilized into milk during lactation.Generally, chemicals enter breast milk bypassive transfer from plasma, and their con-centration in milk is proportional to theirsolubility and lipophilicity (17). Twenty per-cent or more of maternal body burden ofsome persistent pollutants, such as PCBs,can be transferred during 6 months of lacta-tion (18). Information on the toxicokineticsof chemicals in breast milk is incomplete.

Lack of data on health outcomes. Thereare scant data on the health outcomes thatmay be produced in infants by exposures tochemicals via breast-feeding. Thus far, effectson the nursing child have been seen primarilyin high-dose poisonings where the motherwas clinically ill (19). The prospective epi-demiologic studies that are needed to assesschronic outcomes that may occur at lowerlevels of exposure have been undertaken foronly a few chemical contaminants, mostnotably PCBs. Few data exist on long-termeffects or on interactions among chemicals.

Lack of evidence-based health standards.Although most breast-feeding mothers havedetectable levels of several environmentalagents in their milk, there are no establishednormal or abnormal values for clinical inter-pretation that are derived from toxicologicor epidemiologic studies; therefore, evi-dence-based guidance cannot be provided.

To examine these emerging issues and tochart a course for the future, the Mount SinaiCenter for Children’s Health and theEnvironment convened a conference on 5October 2001 titled “Chemical Contaminantsin Breast Milk: Impacts on Children’sHealth.” The stimulus for this conference wasa desire to confront the issue of nursinginfants’ exposure to chemicals in breast milkand to assess the hazards to health and devel-opment that may result from those exposures.A group of scientists and clinicians cametogether to examine what we know and donot know about patterns and trends ininfants’ exposure to chemicals in breast milk,toxicokinetics, possible health outcomes,research needs, and implications for riskassessment. The following are the major find-ings and recommendations of this conference.

Breast Milk Monitoring

The conferees agreed unanimously that aneed exists for a carefully planned and con-ducted national breast milk monitoring effortin the United States. A few countries, mainlySweden and Germany, have systematic breastmilk monitoring programs that have testedconsiderable numbers of women over timeusing consistent sampling methods (15).However, most countries have done littlemonitoring for pesticides, metals, or industrial

chemicals in breast milk. To be nationallyrepresentative, such an effort would need toinclude women of various socioeconomicbackgrounds and geographic locations.

Comprehensive breast milk monitoringwith standardized protocols for specimencollection and analysis must be expandedworldwide. Only with more reliable and bet-ter standardized approaches to selection ofsubjects, milk sampling and collection, andanalytical methods can conclusions be drawnabout global patterns of contamination,trends over time, and emerging hazards.Good data on time trends and geographicpatterns would aid in generating hypothesesand would lead to more definitive studies.Such information would also provide asound basis for evidence-based public healthpolicies. Without such data, it is difficult toprovide advice to health care professionalsand to new mothers on the potential risksand benefits of breast-feeding.

Another need is to study lactatingwomen prospectively to determine rates ofdecrease in concentrations of chemicals overthe course of lactation. It has been recom-mended that women should donate milksamples on a monthly basis (or more fre-quently in the first 2 months) and then every2–3 months if lactation continues (16).

It will also be necessary to develop datathat will permit comparison of breast milkcontamination levels with contaminant levelsassociated with other infant food sources,such as formula and cow’s milk. Such datawill permit us to compare the risks associatedwith each source of infant nutrition. Use offormula feeding does not necessarily result ina child being protected from chemicals in theenvironment because formula can be dilutedwith water that is polluted (15). Infant for-mula has been found to be contaminated withtoxic metals, bacteria, and other environmen-tal toxicants. Pesticide residues and bovinegrowth hormone can be found in cow’s milk.

Health Outcomes

The conferees agreed that to assess the effectsof contaminants in breast milk on child healthand development, it will be necessary to exam-ine children prospectively over many years inlongitudinal epidemiologic studies that usestandardized examination protocols and thatspecifically assess exposures to environmentalcontaminants via breast milk. This is the studydesign envisioned for the National Children’sStudy, a major prospective epidemiologicstudy now being planned under the directionof the National Institute of Child Health andHuman Development in collaboration withthe National Institute of EnvironmentalHealth Sciences, the Centers for DiseaseControl and Prevention, and the U.S.Environmental Protection Agency. The goal

of this study will be to examine the influencesof multiple exposures—environmental, behav-ioral, socioeconomic, and genetic—on childand adult health. It will follow as many as100,000 children in all regions of the UnitedStates, from in utero to at least 21 years of age(20). Companion studies are under develop-ment in Canada and possibly in Mexico. Thechoice of which exposures to measure, whichoutcomes to assess, what data infrastructure tobuild, what specimens to store, and what ethi-cal safeguards to impose will be critical to theNational Children’s Study.

Risk Assessment

The conferees agreed that current risk assess-ment methods generally do not considerchemical exposures to infants via mother’smilk and therefore need to be expanded. Intraditional risk assessment, assessment of riskis normally based on adult body weights andfood consumption data (11).

The level of risk to infants and childrenof exposure to chemical residues in humanmilk depends on each mother’s food con-sumption patterns, the nature and levels ofchemical residues in her milk, and the toxico-logic potency of those chemicals. A compre-hensive analysis of the potential health risksto infants and children exposed to chemicalsfrom breast milk will require consideration ofall these factors as well as of the unique vul-nerabilities of infants and children.

Infants and children may exhibit uniquesusceptibilities to the toxic effects of chemicalsbecause they are undergoing rapid tissuegrowth and development (21). Infants andchildren also consume much greater quantitiesof milk fat and certain foods than do adults ona body weight basis, and thus they may besubjected to proportionately higher levels ofexposure to certain chemicals. These exposuresoccurring earlier in life may predispose infantsand children to a greater risk of chronic toxiceffects than exposure occurring later in life(22). Traditional approaches to health riskassessment need to be expanded to encompassthose factors and to adequately protect infantsand children. Furthermore, it must be recog-nized that there are only limited data on theresidue levels of chemicals in milk and foodconsumption patterns of infants and childrenthat are appropriate for use in risk assessment.

Another source of exposure of infants tochemicals that must be considered in riskassessment is drinking water and the waterused for mixing formulas. Although waterintake is considered in current risk assess-ment, neither nondietary exposures norexposures in drinking water are consideredin deriving risk estimates for total chemicalexposure in infants’ milk. Because of theselimitations, burden of total exposures toinfants and children may be underestimated.

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Stockholm ConventionThe conference concluded by noting thatthere is some encouraging news for nursingmothers. On 22 May 2001, the UnitedStates and 119 other nations signed an inter-national treaty in Stockholm to phase outuse and production of 12 POPs worldwideand established a procedure to add addi-tional chemicals to the list of banned pollu-tants (15). The treaty also promotes actionto minimize the release of biologically persis-tent industrial byproducts such as dioxinsand furans. Over the last several decades,individual nations have banned certainchemicals, effectively reducing the threatthat these chemicals pose. For example, theUnited States has banned DDT and PCBs.Countries that have banned certain POPsare likely to have lower levels of pollutants inmother’s milk. However, even with the sign-ing of the treaty, newly emerging hazardssuch as PBDEs and nonyl phenols must bemonitored (12). Breast milk remains the bestsource of nutrition for babies, but constantvigilance is needed to keep it pure.

REFERENCES AND NOTES

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14. Dewailly É, Ayotte P, Bruneau S, Laliberté C, Muir DCG,Norstrom RJ. Inuit exposure to organochlorines throughthe aquatic food chain in Arctic Quebec. Environ HealthPerspect 101:618–620 (1993).

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18. Niessen KH, Ramolla J, Binder M, Brugmann G,Hofmann U. Chlorinated hydrocarbons in adipose tissueof infants and toddlers: inventory and studies on theirassociation with intake of mothers’ milk. Eur J Pediatr142:238–243 (1984).

19. Rogan WJ. Pollutants in breast milk. Arch PediatrAdolesc Med 150:981–990 (1996).

20. Berkowitz GS, Wolff MS, Matte T, Susser E, Landrigan PJ.The rationale for a national prospective cohort study ofenvironmental exposure and childhood development.Environ Res 85:59–68 (2001).

21. Landrigan PJ. Risk assessment for children and othersensitive populations. Ann N Y Acad Sci 895:1–9 (1999).

22. Committee on Pesticides in the Diets of Infants andChildren, National Research Council. Pesticides in theDiets of Infants and Children. Washington, DC:NationalAcademy Press, 1993.

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