Pesticides in Human Milk: Links with Developmental Problems
Introduction: (summary): Developmental vulnerability to effects of pesticides is authoritatively recognized to be especially high postnatally.
Section A: (summary): Human milk in developed as well as developing countries has been found to normally contain many pesticides. Infant formula in the U.S. has been authoritatively found to contain essentially no detectable pesticides. (Full text, including references to authoritative sources, at Section A)
Section B.1: (summary): Although not ordinarily used in developed countries currently, DDT is still widely used in the developing world and (as a result) is present in a high percentage of fruits, vegetables, farmed seafood, and other foods commonly consumed in developed countries. In a 2007 study, autism prevalence was found to be six times as high as normal near California agricultural fields where pesticides related to DDT were applied, and it varied in correlation with distance from the fields and with poundage of pesticides applied; the time of peak correlation of pesticide exposure with autism incidence was found to be in the year after birth. (Full text, including references to sources, at Section B)
Preview of Fig. 1
Correlation between DDT in human milk and test scores in 10 countries and 14 German states
Exposures to the pesticides that have replaced DDT in developed countries also correlate with reduced IQ.
Section B.2 (summary): Pesticide exposure is associated with ASD prevalence.
Section B.3 (summary): There are many reasons to see breast milk as being the predominant source of pesticides to infants during the period of rapid brain development. (For details and sources, see Section B.3)
Section C (summary): Pesticides have also been found to have adverse effects on males, specifically. A study published in 2016 found very unusually high ratios of adverse effects of common pesticides on motor and social developments of boys, with little or no adverse effects on girls. (Full text, including references to sources, at Section C)
Introduction: Pesticide effects and comparative exposures of infants:
Although pesticides have apparently not been officially designated as neurodevelopmental toxins, there are good reasons to believe that they should be so designated. According to a European/American team of scientists, many pesticides used in agriculture “target the nervous system of insect pests,” which is of special concern because of the “similarity in brain biochemistry” between insects and humans.1 A commission of the U.S. National Research Council (of the National Academies), in a report entitled, “Pesticides in the Diets of Infants and Children,” refers to “specific periods in development when toxicity can permanently alter the function of a system;” such periods of special vulnerability to toxins were said to apply to development of the central nervous system, which the commission says “may demonstrate particular sensitivity (to toxins) during the postnatal period.”2
In a 2006 study in which breast milk samples from Denmark and Finland were examined, 13 different pesticide residues were detected in each of at least 90% of the 130 breast milk samples tested, in addition to other pesticides found less frequently. The average concentrations were over 10 times the lowest concentrations measured, and there was no indication that the lowest levels measured were especially low.3 A 2011 study (Weldon et al.), investigating pesticides in breast milk samples from the urban Bay Area and a rural area in California, found detection rates of chemicals (mostly pesticides, but also PCBs and degradates of DDT) similar to the above; the authors noted that their findings for urban populations were very similar to those for agricultural populations, and attributed the urban exposure mainly to pesticides in foods.4
See Section B.3 below for much more information about how very substantial the pesticides in human milk are; and see Section B.2 below for evidence of strong adverse effects of those toxins on child development as a result of current levels of human background exposure.
Quoting from a publication of a commission of the U.S. National Academy of Sciences, “measurements have consistently demonstrated that no pesticides are detected in finished infant formulas. These invariably negative analytical findings are attributable to ingredient selection and processing procedures that reduce the potential for pesticide residues to appear in the finished product.”5 (italics added) In 2013, the U.S. Department of Agriculture reported testing over 300 samples of infant formula and finding no detectable pesticide in 100% of dairy-based formula tested and in 99.4% of samples of soy-based formula that were tested.6
Section B.1: Exposures of children to pesticides at current background levels correlate well with reduced mental capacities.
According to a 2012 article by Dr. David Bellinger, professor at the Harvard School of Public Health and author (contributing or primary) of over 250 published studies, the total loss of IQ points in American children associated with exposure to organophosphate pesticides alone is over twice as great as the total losses associated with ASD (autism spectrum disorders).7 A study done for the European Union found similar loss of IQ points in the EU associated with exposures to organophosphates, as well as almost 60,000 cases of intellectual disability annually in the EU, at total cost of about 146 billion Euros per year (over $160 billion);8 the authors' focus was on damage to the developing brain by widespread environmental chemicals during the period spanning fetal development through puberty.
Organochlorine pesticides, including DDT, have by now been banned for most uses in most developed countries, but their continued use (for malaria control as well as agriculture) in developing countries means that they are widely present not only in those countries but also in a high percentage of fruits, vegetables, farm-raised seafood, and other popular food consumed in developed countries, since much of that food is imported.9, 10
Considering the continuing widespread exposures to organochlorine pesticides (including DDT), the following results from a 2002 study should be of considerable interest: Average DDT levels were measured in mothers at time of birth in various geographic areas (10 countries and 14 German states); 15 years later, higher average time-of-birth DDT levels correlated well with lower average mental capacities in school-age children in those same locations. (see chart below)
The possibility that the correlation was mainly related to prenatal exposures should be considered. But prenatal exposures to most such toxins are small (due to the effect of the placental barrier) compared with postnatal exposures via breastfeeding;11 the postnatal period is one of continued high vulnerability, and often higher-than-prenatal vulnerability, to effects of toxins. (see Section 2 at www.pollution-effects.info)
Notice in the bottom line of data above, showing data for Total DDT as found in studies carried out in South Africa, that the mean (average) level of DDT residues in bovine milk was found to be less than a quarter of the maximum residue limit (MRL) for bovine milk; on the other hand, mean breast milk levels of DDT were found to be 15 times that same MRL.12
Autism and pesticides: When summarizing data from 37 unique studies, the authors of a 2014 review article (Rossignol et al.) found that 34 studies (92%) reported an association between estimated exposures to environmental toxicants and ASD. Most of the reviewed studies were said to have had good study designs, and “the toxicants that appeared to have the strongest association with ASD were pesticides and air pollutants.”13 (emphasis added)
Another 2014 review article generalized concerning effects of pesticides that "most give rise to neurotoxicity."14 Based on seven epidemiological studies determined to be of high quality, elevated risk of autism associated with pesticide exposure was found "with large enough impact and statistical precision to rule out sampling error."
For much more information about close links between ASD and pesticides, including six-fold increase in odds of autism near agricultural fields where pesticides were applied, and including pesticides transferred via lactation, see Section 4.a.2.2 of www.pollution-effects.info.
ADHD and pesticides: In a 2010 study it was found that, for the most commonly detected metabolite of organophosphate pesticides, children with levels higher than the median of detectable concentrations had twice the odds of ADHD compared with those with non-detectable levels.15 Note that this doubled risk of ADHD applied to 50% of the child population that had detectable concentrations of this specific pesticide; bear in mind that many pesticides have been detected in the breast milk of each of 90% of women in studies, mostly in concentrations many times the limit of detection;16, 4 the above study's finding implies that a large part of the child population in general appears to be at risk for ADHD as a result of very typical exposure to pesticides.
Given the above, remember (from Section A) the authoritatively-determined high levels of pesticides in human milk and the near absence of them in infant formula; those are the two main alternative feedings ingested during the early postnatal period when the brain’s development is highly vulnerable to toxins. (see Section 9.b of www.pollution-effects.info)
Evidence for that, in addition to that already presented in Section A, follows:
-- Concentrations of DDT and some PCBs were found to be ten times as high in breastfed infants as in bottle-fed infants after six months of breastfeeding, in a 2005 study in Germany;18
--- Organochlorine concentrations (including metabolites of DDT, which is the best-known organochlorine) were found to be still four times as high in breastfed infants as in bottle-fed infants at age four, and still over twice as high at age 14; those findings were from a 2015 study in a western country (Spain) in which DDT was banned in 1977.19
-- A relevant statement was made in 2006 by two leading experts on toxins involved in child development, P. Grandjean and P.J. Landrigan, each of whom are first or contributing authors of hundreds of scientific studies; they reported that “specific pesticides ... are passed on to the infant via breast milk, resulting in infant exposure that exceeds the mother’s own exposure by 100-fold on the basis of bodyweight.”20 (Many or most pesticides, including the major organochlorine and organophosphate types, are lipophilic21 -- attracted to fat -- and therefore become concentrated in breast milk.22)
-- As pointed out in more detail in Section A: In what have apparently been the major published studies about pesticides contained in human milk (in Denmark, Finland and the U.S.), many different pesticides were found in the milk of over 90% of all women, in urban as well as agricultural areas; the average pesticide concentrations were over 10 times the lowest concentrations measured. This compares with no pesticides found in over 99% of all samples of infant formula.
-- According to the U.S. National Research Council, "The gastrointestinal tract is the major portal of entry of pesticides into the body."24 (italics added) If infants are breastfed for the recommended six months or more, especially if exclusively breastfed as recommended, that leaves little doubt as to the greatest source of exposure to pesticides during the developmentally vulnerable early period after birth.
-- Infants would not normally be at the stage of hand-to-mouth activity until after 6 months of age,25 which means that infant exposures from surroundings would usually be minimal during what is likely to be the most sensitive period of postnatal development. (see Section 2.d of www.pollution-effects.info)
Bear in mind (from www.male-development.info) the unexplained very high ratios of males to females among children affected by the increasing neurological disorders (especially ASD and ADHD), as well as the disproportionate cognitive deficiencies of young males in the general population in recent years. In addition to the studies included in the Rossignol et al. review in Section B.2 (it came later), was a 2016 Chinese study that found postnatal exposures of human children to typical contemporary (organophosphorous) pesticides to have adverse sex-specific neurological effects as follows: The odds ratios for developmental delay in the motor area of boys with higher concentrations of DE and DAP pesticide metabolites were 264 to 1 and 145 to 1. The adverse effect of postnatal concentrations of DE on the social area of boys was in a ratio of 57 to 1.28
As the author of the above, my role has not been to carry out original research, but instead it has been to read through very large amounts of scientific research that has already been completed on the subjects of environmental toxins and infant development, and then to summarize the relevant findings; my aim has been to put this information into a form that enables readers to make better-informed decisions related to these matters. The original research articles and government reports on this subject (my sources) are extremely numerous, often very lengthy, and are usually written in a form and stored in locations such that the general public is normally unable to learn from them.
My main qualification for writing these publications is ability to find and pull together large amounts of scientific evidence from authoritative sources and to condense the most significant parts into a form that is reasonably understandable to the general public and also sufficiently accurate as to be useful to interested professionals. My educational background included challenging courses in biology and chemistry in which I did very well, but at least as important has been an ability to correctly summarize in plain English large amounts of scientific material. I scored in the top one percent in standardized tests in high school, graduated cum laude from Oberlin College, and stood in the top third of my class at Harvard Business School.
There were important aspects of the business school case-study method that have been helpful in making my work more useful than much or most of what has been written on this subject, as follows: After carefully studying large amounts of printed matter on a subject, one is expected to come up with well-considered recommendations that can be defended against criticisms from all directions. The expected criticisms ingrain the habits of (a) maintaining accuracy in what one says, and (b) not making recommendations unless one can support them with good evidence and logical reasoning. Established policies receive little respect if they can’t be well supported as part of a free give-and-take of conflicting evidence and reasoning. That approach is especially relevant to the position statements on breastfeeding of the American Academy of Pediatrics and the American Academy of Family Physicians, which statements cite only evidence that has been
(a) selected, while in no way acknowledging the considerable contrary evidence,a1 and
(b) of a kind that has been authoritatively determined to be of low quality.a1a - a2c
When a brief summary of material that conflicts with their breastfeeding positions is repeatedly presented to the physicians’ associations, along with a question or two about the basis for their breastfeeding recommendations, those associations never respond. That says a great deal about how well their positions on breastfeeding can stand up to scrutiny.
The credibility of the contents of the above article is based on the authoritative sources that are referred to in the footnotes: The sources are mainly U.S. government health-related agencies and reputable academic researchers (typically highly-published authors) writing in peer-reviewed journals; those sources are essentially always referred to in footnotes that follow anything that is said in the text that is not common knowledge. In most cases a link is provided that allows easy referral to the original source(s) of the information. If there is not a working link, you can normally use your cursor to select a non-working link or the title of the document, then copy it (control - c usually does that), then “paste” it (control - v) into an open slot at the top of your browser, for taking you to the website where the original, authoritative source of the information can be found.
The reader is strongly encouraged to check the source(s) regarding anything he or she reads here that seems to be questionable, and to notify me of anything said in the text that does not seem to accurately represent what was said by the original source. Write to email@example.com. I will quickly correct anything found to be inaccurate.
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a1a) Studies that support breastfeeding are essentially all of the observational type, according to former U.S. Surgeon General Benjamin, in The Surgeon General’s Call to Action to Support Breastfeeding 2011, p. 33, at www.surgeongeneral.gov/library/calls/breastfeeding/calltoactiontosupportbreastfeeding.pdf
a2) Figure 2 in Guyatt et al., GRADE guidelines: 1. Introduction -- GRADE evidence profiles and summary of findings tables, Journal of Clinical Epidemiology, at http://www.jclinepi.com/article/S0895-4356(10)00330-6/pdf
a2a) Dr. Gordon Guyatt is chief editor of User’s Guides to the Medical Literature: A Manual for Evidence-based Clinical Practice, 2nd Edition (3rd is upcoming), copyright American Medical Association, published by McGraw Hill.
a2b) Dr. David Sackett writing in The Canadian Medical Association Journal, as quoted in “Do We Really Know What Makes Us Healthy?” New York Times, published: September 16, 2007 at http://www.nytimes.com/2007/09/16/magazine/16epidemiology-t.html?pagewanted=2&_r=0
a2c) In a review in the Journal of the Medical Library Association, only two guides are recommended for use by physicians in evaluating evidence in medical literature, one of which is the one edited by Guyatt et al., already referred to, and the other of which is by Dr. Sackett. (Journal of the Medical Library Association, Oct. 2002, User’s Guide to the Medical Literature: A Manual for Evidence-Based Clinical Practice, Review by Rebecca Graves, at httpi://www.ncbi.nlm.nih.gov/pmc/articles/PMC128970)
2) Pesticides in the Diets of Infants and Children, Commission on Life Sciences, National Research Council, National Academy Press, Washington, D.C. 1993, p. 43 at http://www.nap.edu/openbook.php?record_id=2126&page=43
Also, for a more recent study finding disproportionate ratios between organohalogens in breast milk versus those in cord tissue and cord serum, see Needham et al., Partition of Environmental Chemicals between Maternal and Fetal Blood and Tissues, Environ Sci Technol. Feb 1, 2011; 45(3): 1121-1126, at http://pubs.acs.org/doi/pdf/10.1021/es1019614, Table 2, finding weight-based concentrations of organohalogens to be over 30 times higher in human milk than in umbilical cord tissue.
19) Fig. 3 of Gascon and eight others: Temporal trends in concentrations and total serum burdens of organochlorine compounds from birth until adolescence and the role of breastfeeding, Environment International, Volume 74, January 2015, Pages 144–151, at http://www.sciencedirect.com/science/article/pii/S0160412014003043 )
Banning DDT in Spain in 1977: Zumbado et al., Inadvertent exposure to organochlorine pesticides DDT and derivatives in people from the Canary Islands (Spain), Science of the Total Environment 339 (2005) 49– 62, 2004,
27) Bradman et al., Determinants of Organophosphorus Pesticide Urinary Metabolite Levels in Young Children Living in an Agricultural Community, International Journal of Environmental Research and Public Health ISSN 1660-4601, Table S-4, at http://www.mdpi.com/1660-4601/8/4/1061
28) Liu et al., Adverse Associations of both Prenatal and Postnatal Exposure to Organophosphorous Pesticides with Infant Neurodevelopment in an Agricultural Area of Jiangsu Province, China, Environ Health Perspect, May, 2016, DOI: 10.1289/EHP196, at http://ehp.niehs.nih.gov/EHP196/