Pesticides and Breastfeeding
Betty Crase
LLLI Breastfeeding Reference Library & Database
From: LEAVEN, Vol. 30 No. 3, May-June 1994, pp. 37-40
Ed. Note: We provide
articles from our publications from previous years for reference for our Leaders
and members. Readers are cautioned to remember that research and medical information
change over time.
Very few people any longer
dispute the basic physiological and psychological superiority of human
milk and breastfeeding. In this contaminated world in which we live,
however, some wonder if human milk and breastfeeding can still be unequivocally
recommended for every mother and baby? And what about the alternative
for baby, infant formula? What steps can a woman take during pregnancy
and lactation to minimize her, and consequently her developing baby's,
exposure to pesticides and other organochlorine environmental toxins,
such as DDT, DDE, PCBs and associated dioxins and furans, heavy metals
such as lead, cadmium, and mercury, and others? Let's begin by taking
a look at what we already know and what we must make our best educated
guesses about for the future.
One well known and respected
researcher in the contaminant field, Dr. Walter Rogan, works for the
Epidemiology Branch of the National Institute of Environmental Health
Sciences, Research Triangle Park, North Carolina. Along with his colleagues,
Dr. Rogan has spent fifteen years doing a prospective, ongoing study
of North Carolina mothers and their children. It is interesting to see
how his research has progressed and his viewpoint has changed over the
years.
In 1980 in the New England
Journal of Medicine, Dr. Rogan reviewed what was then known about "Pollutants
in Breast Milk," namely PCBs and the pesticides DDT, dieldrin,
heptachlor, and chlordane. He began by reiterating that these chlorinated
pesticides are lipid soluble, gradually accumulating in the general
population's body fat over long-term exposure and being concentrated
in the lipids of human milk. As a matter of fact, lactation is the main
route of elimination of these persistent chemicals from the female body.
He also pointed out that
it's very difficult to accurately quantify the amounts of these organohalides
in breast milk because levels vary widely from the beginning of a feed
to the end, as well as throughout the day in any one sample of breast
milk from any one woman. The findings of different research studies
are also difficult to compare depending on whether reported contaminant
levels were determined from whole milk or milk fat, which can give substantially
higher values.
Dr. Rogan examined a number
of previous studies which found that PCBs and DDT and its derivatives
were present in virtually all human milk samples from all over the world,
even though DDT was banned in the USA in 1972 and PCBs in 1976. They
are still in widespread use in other areas of the world.
PCBs, used mainly in the
electrical industry as transformer-insulating fluids, leaked in huge
concentrations into rice oil in Japan and Taiwan in the late 1960s and
1970s, respectively. Adult health consequences included an acne-like
rash, headache, nausea, and diarrhea. Newborns were small for gestational
age, had dark skin pigmentation, conjunctivitis, and jaundice. Children
who were breastfed had higher blood levels of PCBs and levels increased
with the duration of breastfeeding. Follow-up of some of these children
at about nine years showed slight but clinically significant neurologic
and developmental impairment. This was an unusual exposure, not an everyday
occurrence.
There were no reports of
DDT toxicity in either occupationally exposed workers or experimentally
exposed volunteers receiving doses considerably greater than in the
general population.
Animal studies were a different
story, however, but Dr. Rogan cautioned about equating effects in animals
with humans. Animal infants, particularly monkeys, have less body fat
than human infants, so contaminants are more likely to attack target
organs. Rogan acknowledged that further studies needed to be done, and
he has proceeded to do one of the best.
In 1986, Rogan and others
published the first in a continuing series of reports on milk samples
from about 900 women in North Carolina and the development of their
children, born between 1978 and 1982. This 1986 study published in the
American Journal of Public Health specifically measured levels of PCBs
and DDE in human milk, blood, and other body tissues at birth, six weeks,
three months and six months, and from some of the mothers, at one year,
and eighteen months.
Almost all samples showed
detectable levels of both PCBs and DDE. The highest levels were in older
women, Black women, first-time mothers, cigarette smokers, and alcohol
drinkers. PCBs, in particular, were higher in women consuming sport
fish during pregnancy. Another important finding was the decline in
contaminant levels in the milk during the course of lactation and with
the number of children breastfed.
A second study in 1986 published
in the Journal of Pediatrics, was the first to report on about 900 of
the North Carolina children and the "Neonatal effects of transplacental
exposure to PCBs and DDE." There were no associations between PCB
and DDE levels and birth weight, head circumference, and hyperbilirubinemia.
The Brazelton Neonatal Behavioral Assessment Scales were administered
after birth. Both chemicals were associated with hyporeflexia (lower
reflex response). Higher PCB levels were also associated with hypotonicity
(lower muscle tone). At that time, Rogan expressed concern about continued
exposure to PCBs and DDE through breastfeeding.
In 1987, the next report
followed the children to one year of age; it was published in the American
Journal of Public Health. The purpose of the study was to ascertain
if the presence of PCBs and DDE in their mothers' milk had affected
these children's growth or health. Neither chemical showed an adverse
effect on weight or frequency of doctors' visits for illness, although
differences were seen between breastfed and bottle-fed children. Bottle-fed
children tended to weigh more and have more frequent gastroenteritis
and otitis media.
In 1988 in the Journal of
Pediatrics, it was reported that the children were examined for any
mental and psychomotor developmental effects at one year of age from
transplacental exposure to PCBs and DDE. Higher transplacental exposure
to PCBs was associated with lower psychomotor scores at both six and
twelve months of age. The key finding here was that exposure to either
chemical through breastfeeding was unrelated to the Bayley Scales of
Infant Development test scores. No adverse effects on growth or occurrence
of illnesses in the first year of life have been attributed to the presence
of these chemicals in human milk.
In 1991 three more studies
in this series were published:
A study published in the
Annals of Epidemiology looked at "Child Development at Eighteen
to Twenty-four Months" versus PCBs and DDE exposure. The trend
toward lower psychomotor scores on the Bayley tests was still present
and determined to still be due to transplacental exposure to the chemicals.
There was no evidence of any effect from the larger but later exposure
through breast milk, but at that time, Rogan expressed concern that
such effects might show up as the children reached an older age.
Another study in the Journal
of Pediatrics followed up the children, now age five-and-a-half to ten-and-a-half
years, with the McCarthy Scales of Children's Abilities and by checking
report cards, when available, to see if the psychomotor deficit through
two years of age, due to transplacental but not breastfeeding exposure
to PCBs, was still present. The deficits seen at two years on the Bayley
Scales of Infant Development were no longer apparent.
The third 1991 study in Regulatory
Toxicology and Pharmacology was particularly important. Rogan and colleagues
developed various types of mathematical analyses to answer concerns
about possible lifetime cancer risks from human milk exposure to chemical
contaminants. The pesticides considered were DDT, chlordane, heptachlor,
dieldrin and their metabolites, and industrial compounds or byproducts,
such as PCBs and dioxins.
An initial statement was
made in that article that the contaminant levels in human milk would
prevent its sale as a commercial food for infants, based on current
standards. This type of statement is made quite casually from time to
time, with no regard for the concern it causes breastfeeding mothers.
Regulatory standards have
been set by the World Health Organization and US Food and Drug Administration
to attempt to control the levels of contaminants in foods. Current "allowable"
levels have been set low to prevent toxicity in adults from exposure
over a lifetime. In reality, there is a range in concentration of the
chemicals, sometimes 100 to 1000 times higher, over which no adverse
reactions have been reported. It is also important to remember that
human milk constitutes only one very limited route and time of exposure
to contaminants over an individual's lifetime. In addition, the rapidly
growing infant is gaining body fat, and thus a place to effectively
store contaminants, during the time it is receiving human milk. What
this means is that even though human milk may contain higher levels
of contaminants than some commercial food stuffs, there are substantial,
built-in safety margins.
Rogan's analytical methods viewed risk from:
- EXPOSURE
to these chemicals in human milk over the duration of breastfeeding,
- CARCINOGENICITY of the various chemicals,
- LIFE EXPECTANCY based on death rates from cancer attributable to the chemicals,
- POSTNEONATAL MORTALITY differences
between breastfed and bottle-fed children, including the well-documented
two-and-a-half times increased risk of death in the first two years
of life from not being breastfed,
- CHANGE IN LIFE EXPECTANCY between
breastfed and bottle-fed children, assuming that breastfed children
have excess cancer risk from the contaminants.
The results were quite striking.
Estimated loss of life expectancy from cancer from human milk exposure
to the contaminants studied was less than three days; in contrast, the
decrease in life expectancy from excess postneonatal mortality in infants
not breastfed compared to the increase in life expectancy in breastfed
infants is about seventy days. There was not only no advantage to avoiding
breastfeeding, there was a disadvantage. Breastfed children, even those
at the extreme doses of contaminants considered to be in human milk,
had a net lower risk of death and longer life expectancy.
Rogan concluded that at current
levels, the estimated cancer risks associated with contaminants in breast
milk do not outweigh the benefits of breastfeeding. Because of these
results, he also questioned the usefulness of testing human milk for
contaminants in the general population, although he felt that individual
women facing occupational or accidental exposure from PCBs in particular
might consider testing.
In 1992 in NeuroToxicology,
Rogan once again reviewed what had been learned in the preceding years
about the neurotoxicology of PCBs and related compounds. Information
about breastfed children concluded that despite the presence of PCBs
in breast milk, no association between breast milk exposure and any
measured outcome has been seen other than lower activity levels at four
years among long-term breastfed children at the highest PCB levels.
And finally, in 1993 in Early
Human Development Rogan examined breastfeeding and cognitive development
in the children he had followed for so long. What he discovered was
that the breastfed children, even though they had received higher contaminant
loads through human milk than the children who had been bottle-fed from
birth, scored significantly higher on the Bayley and McCarthy mental
and psychomotor development tests (at all time points from two years
through five years) and had higher English grades on report cards from
grade three or higher. There were also trends toward higher scores with
increasing length of breastfeeding. Rogan concludes that breastfeeding,
even with known contaminants in human milk, offers the potential for
enhancing the children's development within the population at no risk
and little cost.
So, in answer to one of my
original questions--can breastfeeding still be recommended for infants
in this contaminated world.? Yes, and the research is there to confirm
that answer.
But what about the contaminants
found in the infant feeding alternative, commercial infant formula?
The Rogan series of studies
cited earlier also analyzed cow's milk and infant formula that was being
fed to infants and children not receiving human milk. No overall significant
levels of pesticides and organochlorine contaminants were found, although
individual samples may be higher.
Even though processing standards
and contaminant limits have been set in the USA, remember that cows
are part of the contaminated environment, eating grasses, grains, and
other feed potentially treated with pesticides and drinking water potentially
contaminated with a variety of chemicals. Dairy cattle are also treated
with a variety of drugs, including antibiotics, and these can find their
way into the milk supply as well as potentially into infant formulas
which are predominantly cow's milk-based.
One set of compounds not
yet discussed are the heavy metals, such as lead, cadmium, and mercury.
The heavy metals bind more readily to human milk proteins as opposed
to the previously described pesticides and organochlorines which bind
to lipids.
In general population exposure,
lead levels in human milk are normally lower than the lead levels in
milk-based infant formulas. This is especially true when concentrated
infant formulas are mixed with water containing high lead levels or
packaged in lead-soldered cans. There are generally higher blood lead
levels in formula-fed infants than breastfed infants, too. The February
1994 issue of Pediatrics takes an extensive look at the lead
crisis in infants in general, including the continuing controversy over
the new lower blood lead concentration limit recently set.
Cadmium levels in breast
milk are about the same as in cow's milk. Please note, however, that
cadmium and DDT levels are higher in the breast milk of smokers.
Mercury levels typically
are lower in human milk than those of lead and cadmium. The highest
levels have been found in the milk of fish eaters, particularly sport
fish. Concern is also raised from time to time about the contribution
of mercury to human milk from silver amalgam dental fillings. This bears
research investigation.
Much of the preceding information
comes from a highly respected reference text entitled Chemical Compounds
in Human Milk, edited by two world-renowned researchers in the field,
Allan A. Jensen of the Danish Institute of Technology, Department of
Environmental Technology, and Stuart A. Slorach of the Food Research
Department at the Swedish National Food Administration. This text reviews
the global contaminant picture and its impact on human milk to 1991
in terms of general population versus occupational exposure.
Other facts of interest from
this book include the following:
Dietary intake of contaminants
during lactation is not a significant source of contamination in breast
milk; the contaminants come from the mobilization of adipose tissue
into the lipids in human milk. During pregnancy, however, dietary intake
may significantly affect maternal contaminant levels because of an increase
in adipose tissue in conjunction with weight gain, as well as development
of key organ systems in the fetus itself.
Contaminant levels are also
dependent on personal exposure from a woman's location in the environment.
There are higher levels of persistent organochlorines in women living
in coastal regions, presumably from eating more readily available fish.
However, women who consume great quantities of beef and dairy products
should also be aware of concerns.
There are lower levels of
DDT and DDE in the milk of vegetarian mothers, but stable PCB levels
indicate that contaminant sources other than food are involved, for
example air pollution outdoors and indoors.
The following quotation sums
up the risk-benefit considerations as summarized in this authoritative
text:
Reports in the mass media
about the presence of toxic chemicals in breast milk often alarm mothers,
who wonder whether they should get their milk analyzed and, if the levels
are relatively high, stop breastfeeding. Virtually all national and
international expert committees have hitherto concluded--on the basis
of available information--that the benefits of breastfeeding outweigh
the possible risks from chemical contaminants present in human milk
at normal levels. There is little point in investigating milk from individual
concerned mothers, unless there are indications of abnormally heavy
exposure, for example, at the workplace or due to poisoning incidents.
References
Gladen, B. C. et al. Development
after exposure to dichloroethene polychlorinated biphenyls and dichlorodiphenyl
transplacentally and through human milk. J Pediatr 1988; 113(6):991-95.
Gladen, B. C. and W. J. Rogan.
Effects of perinatal polychlorinated biphenyls and dichlorodiphenyl
dichloroethene on later development. JPediatr 1991; 119(1pt1):58-63.
Jensen, A. A. and S. A. Slorach,
eds. Chemical Contaminants in Human Milk 1991; Boca Raton, Florida:
CRC Press, Inc.
Rogan, W. J. et al. Pollutants
in breast milk. N Engl J Med 1980; 302(26):1450-53.
Rogan, W. J. et al. Polychlorinated
biphenyls (PCBs) and dichlorodiphenhyl dichloroethene (DDE) in human
milk: effects of maternal factors and previous lactation. AJPH
1986; 76(2):172-77.
Rogan, W. J. et al. Neonatal
effects of transplacental exposure to PCBs and DDE. J Pediatr
1986; 109(2):335-41.
Rogan W. J. et al. Polychlorinated
biphenyls (PCBs) and dichlorodiphenyl dichloroethene (DDE) in human
milk: effects on growth, morbidity, and duration of lactation. AJPH
1987: 77(10) :1294-97.
Rogan, W. J. and B. C. Gladen.
PCBs, DDE, and child development at 18 and 24 months. Ann Epidemiol
1991; 1(5):407-13.
Rogan, W. J. et al. Should
the presence of carcinogens in breast milk discourage breast feeding?
Reg Toxicol Pharmacol 1991; 13:228-40.
Rogan, W. J. and B. C. Gladen,
Neurotoxicology of PCBs and related compounds. NeuroToxicology
1992; 13:27-36.
Rogan, W. J. and B. C. Gladen.
Breast-feeding and cognitive development. Early Human Dev 1993;
31:181-93.
Wolff, M. S. et al. Blood
levels of organochlorine residues and risk of breast cancer. JNCI
1993: 85(5):648-52.
Minimizing Contaminant Risks During Pregnancy and Lactation
- Thoroughly wash
and peel fruits and vegetables to eliminate the hazard of pesticide
residues on the skins;
- Limit your intake
of dairy products, realizing that the lower the butter fat,
the lower the potential burden of fat-soluble contaminants;
- Reduce consumption
of red meats, taking care to trim off excess fat which contains
contaminants;
- Remove skin and
excess fat from chicken;
- Avoid freshwater
fish and other marine animals from known contaminated waters
to avoid PCBs and mercury, in particular;
- Eat foods lower
on the food chain, for example, eating grain rather than eating
beef or other animals that have been fed grains;
- Avoid excessive
weight loss through crash dieting which suddenly releases greater
amounts of the fat-soluble contaminants, such as PCBs, into
the bloodstream;
- Avoid smoking
cigarettes and drinking alcohol as levels of contaminants have
been found to be higher in those who smoke and drink;
- Limit the use
of home, garden, and lawn pesticides as these are related to
increased levels of DDT in breast milk; be sure to discard containers
in the garage and workroom as these are possible sources of
direct exposure to curious children;
- Discontinue the
use of cosmetics made from contaminated raw materials such as
lanolin prepared from the wool fat of sheep treated with persistent
pesticides; use only a medical grade of lanolin such as Lansinoh(R)
for sore or cracked nipples during breastfeeding;
- Avoid homes and
buildings that have been treated for termites with chlordane
or dieldrin;
- Avoid contact
with incineration smoke and ash, preserved wood, or produce
grown near incinerators; incineration discharge contains almost
the full spectrum of chemical and industrial toxins, including
the heavy metals.
- Avoid occupational
exposure to chemical contaminants, demand that the workplace
set safety standards considering pregnant and lactating women
as the models.
- Beware of indoor
pollution and high levels of PCBs, especially in kitchens and
offices with electric installations.
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