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Mother's Milk or Mother's Poison? Pesticides in Breast Milk

By Ruth M. Heifetz and Sharon S. Taylor

In the year of the tainted apple,' it seems appropriate to explore whether human breast milk also shows the presence of pesticides. The fate 1970s and early 1980s witnessed a tremendous resurgence of breast-feeding. Sixty percent of newborns were breast-fed in contras" to the fate 1960s and early 1970s when only 25% of infants who left the hospital were breast-feeding.2 The advantages of breast-feeding are well established: it offers superior nutrition, protection against infection, enhancement of the immune system, a contraceptive effect while lactating, economic benefits, and emotional support.3 However, breast-feeding shifted from being the norm in the early years of this century, to the low points described in the 1960s and early 1970s, as a result of the aggressive marketing by infant formula companies:

This shift from breast-fed to "bottle babies" was also dramatic and particularly tragic in the developing world. Formula feeding's impact on families living in severe poverty was catastrophic. Infant diarrhea, severe malnutrition, increased infections, and` a tragic bounty of preventable illness and death were all consequences of this shift from breast to bottle in the developing world.4

Pesticide residues found.

"Although environmental contaminants may have potential for entering breast milk, pesticides. are among the groups with greatest concern," states one author in Clinical Nutrition. Pesticides such as chlordane, heptachlor, DDT, DDE and other organohalogen compounds do not biodegrade in the environment. Instead they bioconcentrate and are stored in the fat of human beings, who feed at the top of the food chain. The infant feeding on its mother's milk is even higher on this chain.5

In the 1960s, many articles signaled the presence of pesticides in human milk. However, surveys as early as 1948, 1949, and 1951 had already found traces of DDT in one-quarter of market samples of cow's milk in the U.S .6 In 1978, reports indicated that during the previous years of that decade, 96 percent of commercial milk samples in Illinois had dieldrin residues, 93 percent had heptachlor epoxide, 73 percent had lindane, 69 percent had chlordane, and 48 percent had DDT residues.

Because cow's milk had become contaminated with widely used insecticides, it should have been of considerable interest to explore the state of human milk. But the first evaluation of human milk for insecticide contamination did not occur until 1951 when 32 non-occupationally exposed black women were surveyed in Washington, D.C., 30 of whom had detectable levers of DDT with mean value of 0.13 ppm.7

More than a decade passed before another paper was published in the U.S. on the results of a small survey taken in California noting both DDT (0-0.12 ppm) and DDE (0-0.25 ppm) in human milk.8

Since that time many research papers have been published that report on limited surveys of the levers of chlorinated hydrocarbons , principally DDT and its metabolites. There has been considerable variation in the DDT levers, based undoubtedly on significant differences in the variables explored, such as urban and rural differences, age of mothers, occupations, and geographic variability.

E.J. Calabrese comments there does not seem to be a downward trend in DDT levers in human breast milk over the 30 years since the original reports, including the years since DDT was banned in 1970.6 He notes that despite the differences between studies, all reported that breast milk had such high levers of DDT that substantial percentages of nursing infants were ingesting more DDT than was considered acceptable by the World Health Organization.9 Calabrese states that cow's milk containing the average lever of DDT found in human milk would have been banned by the Federal Department of Agricultures

While initial studies focused on DDT in the fate 1960s, other pesticides were identified in reviewing breast milk samples. It was not until 1981 that a national survey of over 1400 nursing women was conducted.' The survey revealed that 83%, 61%, and 74% of the milk samples had detectable levers of dieldrin, heptachlor epoxide . (a breakdown product of heptachlor) and oxychlordane (breakdown product of chlordane), respectively. Most of the studies concerning a spectrum of pesticides document that pesticides continue to be present in the milk of nearly all nursing mothers.

How Does Breast Milk Become Contaminated?

The human breast is capable of producing a liter of milk a day. It is a complex organ that both synthesizes and excretes chemicals. Milk is composed of protein, fat, carbohydrates, minerals, vitamins, hormones and antibodies. Milk contains the fat as droplets suspended in water, an emulsion separated from. the blood plasma by a semipermeable membrane. Chemicals can be excreted into breast milk by binding to milk protein or adhering to the surface of milk fat globules, or they can be totally contained within the fat globules.

Fat soluble materials such as the organochlorines, DDT and chlordane, can be stored for long periods of time in maternal body fat. Body fat mobilization and turnover are increased during lactation and fat soluble substances may also be mobilized. Fat soluble substances may be released from fat during weight loss, which typically occurs during lactation."

Thus past exposures to fat soluble pesticides pose a risk that the breast-feeding mother cannot avoid at the time of pregnancy and lactation, in contrast to other substances like medications, coffee, and recreational drugs. A mother's prior lifetime burden of pesticides represent an important source of pesticides for the fetus and for the infant during breast-feeding.

Fat solubility influences the storage of pesticides in the mother's "issues, their mobilization during lactation, the transfer of pesticides form the mother's blood plasma to the milk, and thus the total dose to the infant. The passage through several barriers is greatly accelerated if a substance is fat-soluble.

In general the very young are open to exposure to pesticides on three levers. The first involves the capacity for toxic materials to get into the brain. The second is based on the fact that the brain is still developing. The third concerns the fact that fat soluble pesticides are "fat seeking." An area of concern with infants is the adequacy of the "blood brain barrier," a special protective feature of the human brain. Thus infants may be particularly vulnerable to exposure to neurotoxic pesticides.'2

Living at the Top of the Food Chain

The actual amount of pesticides that the breast-feeding infant receives is related to the intake during pregnancy via the placenta and the concentration of. pesticides in the breast milk, both of which are related to the maternal body burden, as well as the volume and duration of breast-feeding.

The fat content of a mother's milk actually varies during the nursing process. The milk is longer in fat in the first period of a feeding than the latter period. It has been suggested that infants feeding briefly, but more frequently, might therefore obtain milk with a longer fat content and thus receive a longer dose of fat soluble pesticides

The actual infant pesticide burden is related to the amount available in the breast milk, to the amount actually absorbed by the nursing infant, and to the ability of the infant to remove these substances from its body.

The major routes for elimination of pesticides are through the kidneys and via metabolism, much of which is dependent on effective river functioning. Both these organs are often poorly developed in the very young infant, which decreases the organs ability to, remove toxic substances from the body. Clearance mechanisms are particularly weak in the many low birth-weight infants (not all of whom are preterm).

Low birth-weight infants constitute 6% of all newborns. In high risk populations (e.g., those living in poverty, or born to teenage mothers, those with delayed or absent prenatal care), 12% of the infants will have a low birth weight. These less mature newborns represent a significant number of infants who already have a diminished capacity to survive, since they are more prone to other illnesses and developmental problems. The premature infant may be more vulnerable to milk contaminants not only because of their impaired elimination mechanisms, but because the integrity of the blood brain barrier may be more easily breached. This raises particular concern about entities like pesticides and their pesticide solvent vehicles, both recognized as neurotoxins. The potential for central nervous system damage is great, when one considers that substantial human growth and maturation occur in the brain following birth

Sources of Contamination

Sources of exposure to pesticides for the mother and her nursing infant are ubiquitous. It is important to recognize the potential exposures in the workplace, home, and broader community and the possible routes of transmission.

The list of chemicals of concern includes metals such as lead, mercury and cadmium, and solvents and halogenated hydrocarbons that include many of.the fat soluble pesticides, described as transferring to milk very efficiently due to the high proportion of fat in milk (Table 1). Many workers who are exposed to pesticides on their jobs are not involved in the manufacture of pesticides or in their application in the fields, but are exposed as "bystanders" in offices, transportation activities, hospitals, or parks, where pesticides are used. Many industrial processes use pesticides as antifungal agents, although workers are often unaware of these exposures.

In the home, exposures occur in a myriad of ways: structural pest control activities, gardening, neighborhood drift, and agricultural or government spraying for insect and weed control. In the community, pesticides are still used generously in most locations, in hospitals, schools, parks, markets, theaters and restaurants.

Air, water and food are all vehicles that carry. pesticides to the body. Routes of transmission are the lungs, ingestion, the skin (an extremely effective mode of transmission for pesticides), the placenta during pregnancy, and of course breast-feeding.

Health Concerns

The factors determining how pesticides are stored and released from the nursing mother's body have been reviewed. However, the major issue is to investigate the extent of infants' exposure and the impact on their health. The relatively few studies that exist are difficult to compare, and maternal and infant variables are either inadequately detailed, or difficult to control. The pesticides reviewed are varied, and insufficient information is available concerning the toxicity of their metabolic products.

For instance, it is believed that when DDT breaks clown to DDE, this metabolite decreases the duration of lactation, perhaps through an estrogen effects Very little is known about the fate of pesticides in breast milk; how the levers vary during a single feed, and from one feed to the next as lactation proceeds, and between the early and later phases of breast-feeding.

It is very hard to generalize on the basis of the existing data, which are based in great part on animal studies, or individual human case reports. Obviously, there are no controlled human studies. Unfortunately research in this field has not enjoyed the priority many believe it merits, given the increasing popularity of breast-feeding in our country and the importance of breast-feeding for the developing world.

Our understanding of the impact of pesticides on human health is greatest in the case of acute high lever exposures, but we know very little about the long-term consequences of chronic low-level exposures, which are the main concern with nursing infants. Assessing the hazards to the newborn of exposures to pesticides that are known mutagens, carcinogens, neurotoxins and agents that may disrupt the immune system is an urgent task we face today.

In the case of pesticides, not only do we have sparse and inadequate data, but we know very little about their impact on the very young. There is no agreement on what, if any levers of which pesticides in breast milk are not hazardous. There are virtually no data to substantiate the effects of multiple chemicals at low levers or whether their impact is additive or synergistic. This article has only reviewed the question of pesticides in breast milk. What should also be considered are the health hazards posed by further exposures to dangerous substances after the breast-feeding stage.

Ensuring Future Safety

The safety of the food supply for children is all-important for the future of our planes. We must begin by creating a system that provides adequate information on the quality of mother's milk nationwide, i.e., a comprehensive, monitoring program state by state, or area by area (contaminants are different in each locale). This surveillance program should:

We must stars by creating a system that provides adequate information on the quality of mother's milk nationwide.... "

1. Determine the toxic materials that are likely to be present, given industrial and agricultural activities in the area, in order to test for the appropriate chemicals.

2. Institute a breast-milk testing program, to gather population-based information about specific contaminants and their levers. These data will also provide the basis for charting national and regional trends. Currently such information is severely lacking.

3. Establish a testing program available to individual women with specific concerns, assuring quality and economic accessibility for those requiring clinical assessment.

4. Identify "trot spots" and inform the appropriate health department jurisdictions, local health practitioners, and the community. This information can be the basis for implementing clean-up programs and conducting studies for health effects.

There is a tremendous need to create education programs for health professionals and the general community about toxics and breast-feeding, emphasizing the prevention of avoidable exposures to pesticides and ways of reducing and eventually eliminating their use.

Insist on research concerning toxine in breast milk so that we may feed those at the very top of the food chain safely.


1. Sewell, B.H., Whyatt, R.M. 1989. Intolerable risk: Pesticides in our children's food. New York: Natural Resources Defense Fund.

2. Hendershot, G.E. 1984. Trends in breastfeeding. Pediatrics 74 (suppl):591-602.

3. Jelliffe, D.B., and E.F. Jelliffe. 1979. Early infant nutrition: Breast-feeding in nutrition. In Winick (Ed.), Pre- and post-natal development. New York: Plenum Press.

4. Joseph, S.C. 1981. The infant formula controversy: An international health policy paradigm. Annals of Internal Medicine 95:383-384.

5. Lederman, S.A. 1989. Breast milk constraints: substance abuse, infection and the environment. Clinical Nutrition. 8:120-130.

6. Calabrese, E.J. 1982. Human breast milk contamination in the Untied States and Canada by chlorinated hydrocarbon insecticides and industrial pollutants: Current statue. J. of the Amer. Coll of Toxicology. 1(3):91-98.

7.Laug, E.R, Kunze, F.M., and Prickett, C.S. 1951. Occurrence of DDT in human fat and milk. Arch. Ind Hyg Occup. Med. 3:245-246.

8.West, 1. 1964. Pesticides as contaminants. Arch. Environ. Health 9:626-633.

9. WHO. 1969. Pesticide residues in food--Report of the 1968 joint FAO/WHO meeting. WHO Tech. Report. sec. 417.

10. Savage, E.R, et al 1981. National study of chlorinated hydrocarbon insecticide residues in human milk. USA. Amer. J. Epidem. 1 13:413~422.

I I. Barr, M. Jr. 1981. Environmental contamination of human breast milk. Am. J. Public Health. 71:124126.

12. Gladen, B.C, et al 1988. Development after exposure to polychlorinated biphenyls and dichlorodiphenyl dichloroethene transplacentally and through breast milk. J. Pediatrics 113:991-995.

13.Atkinson, H.C., E.J. Begg, and B.A. Darlow, 1988. Drugs in human milk. Clinical Pharmacokinetics 14:217-240.

14. Ciacoia, C.R, and C.S. Catz. 1979. Drugs and pollutants in breast milk. Clinics in, PerinatoL 6(1):181-196.

15. Rogan, W.J., et al 1987. Polychlorinated biphenyls (PCBs) and dichlorophenyl dichloroethene (DDE) in human milk: Effect on growth, morbidity and duration of lactation Am. J. Public Health. 77:1294-1297.

Citation for this article: Heifetz, M. Ruth, Taylor, S. Sharon 1989, "Mother's milk or mother's poison ? Pesticides in breast milk.", Journal of Pesticide Reform, Vol. 9,.No. 3, Fall 1989, pp. 15-17.

Copyright 1989 Northwest Coalition for Alternatives to Pesticides.

Reprinted with permission.

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