The following question was discussed in the Autism Speaks website in July of 2013, at :


Q:  “If exposure to toxic substances during pregnancy can increase the risk that my child will develop autism, what can I do to reduce my exposure?"


This is our response to that question:

A:  Bear in mind that the developmental toxins that are apparently most harmful are classified as "persistent," which means that if they were present in the mother's body during pregnancy, they will mostly still be there after the birth (along with newly-added toxins), typically being steadily transferred to the developing infant.  Specific toxic components within the pollutants recently identified as being especially closely related to autism include dioxins and PCBs;(1)  both of these are "organochlorine" compounds.  The Danish scientist who is the author of nine studies about chemical contamination of human milk pointed out something of interest concerning that type of toxin: ."much higher doses of organochlorine compounds (from 10 to 20 times higher) penetrate the infant's body via the milk than via the transplacental route."(2)


Postnatal ingestion of these toxins by an infant comes well before autism-related symptoms become apparent.  One of the organochlorines, dioxin, is known not only to be neuro-developmentally toxic and persistent but also to typically be present in contemporary U.S. breast milk in doses scores to hundreds of times higher than the EPA-determined safe threshold.(3)  (And also in concentrations many times higher than in formula.)(4)



A highly-published scientist and Fellow of the American College of Nutrition (Raymond J. Shamberger) concluded, after a study of all 50 U.S. states and 51 U.S. counties, that "exclusive breast-feeding shows a direct epidemiological relationship to autism;" and also, "the longer the duration of exclusive breast-feeding, the greater the correlation with autism."(5)


(Stop a moment and think carefully about the findings quoted just above, which are confirmed by other studies below, and consider them in relation to the passages in italics in the first two paragraphs.)


Two other studies, carried out by MD's and scientists, have come to conclusions similar to the above.  One found that 37% of children diagnosed with autism in a Kentucky study had been breastfed for six months compared with 14% of children in the general Kentucky population.  The other found that 65% of children with ASD in a U.K. study had been exclusively breastfed for at least four weeks, while the comparable figure for the general U.K population was 28%.(6)


Other commenters (and Autism Speaks officials) are encouraged to provide quotations, specific figures, researcher qualifications, and locations of any studies that disagree (or agree) with the above.  Judging by past observations, studies that disagree with the above are likely to have been done in the Sultanate of Oman, or in Japan decades ago before breastfeeding rates and autism had both increased dramatically, or were even carried out online by non-professionals surveying parents who responded to Google ads (Schultz et al).  (Any suggestions of relevant studies should be addressed to and will be inserted below.)


Mercury is the other major toxin recently confirmed to be especially closely linked to autism; and it, also, is heavily transferred to infants after birth.  According to EPA-contracted research, substantial information on this topic indicates that transfer of mercury during just the first 15 days of lactation equals a third of the total transfer that occurs during gestation.(6a) in the EPA document at (Sections 5.22 and 5.3), good reasons are provided to be especially concerned about postnatal infant ingestion of toxins, including that "the brain is especially vulnerable during the brain growth spurt...." 


Notice in this chart that by far the greatest part of this period of the brain's greatest vulnerability comes after birth.




Keep in mind that this several-month postnatal period stands out with regard to vulnerability of the infant brain because of the following:

a) the fact that a very large part of the brain's development takes place during this period, and

b) the fact that human milk is high in known autism-related toxins, toxins which are present during pregnancy but apparently are not transferred nearly as efficiently through the placenta as they are transferred in breast milk.


There is a widely-held view that the developing brain is vulnerable to toxins prenatally but not significantly vulnerable postnatally; but that view is thoroughly contradicted by clear statements from the EPA, the NIH, and the U.S. ATSDR (Agency for Toxic Substances and Disease Registry), and by at least 26 studies that have found greater harm to result from postnatal exposures to toxins than from prenatal exposures.  For many details and authoritative sources for the above, see


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Various studies have found infant formula to be many times lower in toxins than human milk.(7)  The toxins best known to be harmful are emissions from combustion (especially diesel) and from dust around electronics; humans normally have major exposures such as those, but most cows don't.   For considerably more information about toxins that have been found in human milk, comparing those with levels of the same toxins in infant formiula (as found in peer-reviewed scientific studies), go to


It is well established that college graduates in the U.S. (and certain other countries) breastfeed at about twice the rate of high school graduates.  Therefore it shouldn't be a surprise that autism is far higher among children of college graduates than among children of high school graduates.


Studies that have found benefits of breastfeeding have essentially all been of the kind (observational, non-randomized studies, as acknowledged in the U.S. Surgeon General’s Call to Action to Support Breastfeeding, p. 33) that are recognized to be very subject to confounding by underlying other factors that are often the real causes of the "associations" that are found. (Therefore they are subject to false conclusions, as recognized by the U.S. Agency for Toxic Substances and Disease Registry.)  In addition, it is not well known that many scientific studies have found that breastfeeding is associated with higher disease rates in children, often in a dose-response relationship.  These include 18 studies just in the categories of diabetes, asthma and allergies alone, three studies in the area of autism, and one major study showing a strong dose-response relationship of toxins in breast milk with ADHD in the breastfed children.  To read more about those studies, go to



For more information about toxins in relation specifically to autism, see


To read a more complete discussion of claims about benefits of breastfeeding compared with what has actually been happening, as indicated in historical health records (mainly from the U.S. CDC), indicating incidence of these disorders since breastfeeding greatly increased in the U.S. (after 1971), go to




(1) The recent Harvard study (Roberts et al., published June, 2013 at found diesel emissions as well as mercury to be especially closely linked with autism; dioxins and PCBs, which are organochlorines, are major components of diesel emissions, as are PBDEs.


(2) Jensen, A.A. et al, Chemical Contaminants in Human Milk, CRC Press, Inc., 1991. Cited in

Concentration of Persistent Organochlorine Compounds in the Placenta and Milk of the Same Women, Katarzyna Czaja et al., Ch. 21 of Persistent, Bioaccumulative, and Toxic Chemicals I, Robert L. Lipnick et al. editors, ACS Symposium Series, American Chemical Society, 2001.

Findings of above confirmed in animal tests, with even greater contrasts, in Ahlborg et al., Risk Assessment of Polychlorinated Biphenyls (PCBs), Nordic Council of Ministers, Copenhagen.  Report NORD 1992; 26  at


3)  U.S. EPA. Estimating Exposure To Dioxin-Like Compounds - Volume I: Executive Summary   U.S. Environmental Protection Agency, Washington, D.C., EPA/600/8-88/005Ca., 2002, revised 2005 –,  Section II.6, "Highly Exposed Populations", 4/94 (p. 39)  "Using these procedures and assuming that an infant breast feeds for one year, has an average weight during this period of 10 kg, ingests 0.8 kg/d of breast milk and that the dioxin concentration in milk fat is 20 ppt of TEQ, the average daily dose to the infant over this period is predicted to be about 60 pg of TEQ/kg-d." 


Also: At  one can read that the EPA's "RfD" for dioxin is 7 × 10−10 mg/kg-day."  (that is, O.7 pg of TEQ/kg-d)   In the EPA’s “Glossary of Health Effects”, RfD is defined:  “RfD (oral reference dose): An estimate (with uncertainty spanning perhaps an order of magnitude) of a daily oral exposure of a chemical to the human population (including sensitive subpopulations) that is likely to be without risk of deleterious noncancer effects during a lifetime."


Also:  Infant Exposure to Dioxin-like Compounds in Breast Milk, Lorber and Phillips  Volume 110 | Number 6 | June 2002 • Environmental Health Perspectives  


The EPA has apparently not established thresholds for PCBs and PBDEs, but there is ample evidence that current background levels of PCBs and PBDEs are hazardous to children. (see Footnote 7 about PBDEs)


4)  EPA Home/Research/Environmental Assessment: An Evaluation of Infant Exposure to Dioxin-Like Compounds in Breast Milk, Matthew Lorber (National Center for Environmental Assessment, Office of Research and Development, U.S. Environmental Protection Agency) et al.   At http:/


5) Autism rates associated with nutrition and the WIC program.  Shamberger R.J., Phd, FACN, King James Medical Laboratory, Cleveland, OH  J Am Coll Nutr. 2011 Oct;30(5):348-53.  Abstract at  The full text, including the quoted passages, can be purchased for $7 or reference librarians at local libraries could probably obtain it at no charge. 


6) Trends in Developmental, Behavioral and Somatic Factors by Diagnostic Sub-group in Pervasive Developmental Disorders: A Follow-up Analysis, pp. 10, 14   Paul Whiteley (Department of Pharmacy, Health & Well-being, Faculty of Applied Sciences, University of Sunderland, UK), et al.  Autism Insights 2009:1 3-17  at This U.K. study found that 65% of autistic cases had been exclusively breastfed for four weeks. Two other sources (Patterns of breastfeeding in a UK longitudinal cohort study, Pontin et al., and Infant Feeding 1995, Foster et al.) are compatible in showing a 28% comparable rate of breastfeeding in the general U.K. population.  


Also:  Breastfeeding and Autism  P. G. Williams, MD, Pediatrics, University of Louisville, and L. L. Sears, MD, presented at International Meeting for Autism Research, May 22, 2010, Philadelphia Marriot   This study found a 37% rate of breastfeeding among children diagnosed with autism, as compared with 14% with comparable breastfeeding in that state's (Kentucky's) population.


6a)  Exploration of Perinatal Pharmacokinetic Issues  Contract No. 68-C-99-238, Task Order No. 13  Prepared for Office of Research and Development,  EPA, by: Versar, Inc. EPA/630/R-01/004, Section,  at


6b)  Morbidity and Mortality Weekly Report (MMWR) of the U.S. CDC, Lead in Drinking Water and Human Blood Lead Levels in the United States,  August 10, 2012 / 61(04);1-9  Mary Jean Brown, ScD et al.

A 2012 online document of the Agency for Toxic Substances and Disease Registry, "Principles of Pediatric Environmental Health:  Why Do a Child's Age and Developmental Stage Affect Physiological susceptibility to Toxic Substances?", Feb. 15, 2012, in Environmental Health and Medicine Education section, refers to the "developing blood-brain barrier in infants"


6c) (Some researchers consider the blood-brain-barrier to be formed at 4 months after birth.)  Blood brain barrier maturation:implications for drug Development, Rob Webster, Pfizer Global Research and Development. Pharmacokinetics, Dynamics and Metabolism.   At


7)  Due to the large amount of text needed to satisfactorily present the evidence, that information has been placed separately at .



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