Pollutants that have been Found in Breast Milk, and their Significance
Many environmental pollutants have become concentrated in human milk in modern times, especially since the second half of the 20th century. Thousands of chemicals have been introduced into the environment without any testing for safety, and many of them find their ways into breast milk. This has had significant effects on the health and development of breastfed infants, especially in the developed countries where the environmental toxins tend to be higher. The effects on infants of only a few of those contaminants are known (see later paragraphs).
In a U.K. news article headlined, “More than 350 pollutants found in breast milk,” a Government report was quoted as indicating that ”poisonous dioxins have been found in breast milk,” as well as pesticides and “notoriously toxic chemicals used in a whole range of applications from electrical transformers to paint.” And "’some of the contaminants identified are known to have the ability to cause cancer and some are able to impair the immune system. Others are known to interfere with the normal functioning of the bodies' hormones.’ Mothers pass on chemicals that they have stored in their fat all their lives to their babies in their milk.”a On the basis of established knowledge about the problems, the Government was starting a formal survey of pollutants in breast milk including the above chemicals as well as “‘gender bender’ chemicals that disrupt hormones…, and toxic metals such as lead, mercury and arsenic.” To read about some of the better-known, specific toxins that have been found human milk, their known effects on developing infants, and comparisons of their levels in breast milk vs. in infant formula, see www.breastfeeding-toxins.info.
Another major study done on this subject was carried out in 1982 and is only readily available in a PDF file made from a scanned copy of a microfiche copy, with resulting very imperfect appearance; but it is satisfactorily legible.
The samples that were analyzed when compiling this list (the list is continued below) were collected in relatively polluted areas, where atmospheric concentrations would have been expected to be above average. But living far away from major polluters provides no assurance of lack of contamination in human milk, since
1) air pollutants can travel many hundreds or even thousands of miles before coming down to the human environment,
2) some of the most toxic and widespread pollutants -- dioxins, PCBs, PBDEs and mercury-- enter the human body either mostly or to a large extent in foods, especially in meat, fish and dairy products (contamination of those foods results mainly from biomagnification as very small quantities become much more concentrated as they rise in the food chain, especially mercury in fish), and
3) relatively common local air pollution has been found to be very closely linked with autism. In a major Harvard University study published in 2013, several atmospheric pollutants at time and place of birth were found to be closely connected with likelihood of later autism diagnosis of the child.(1) The population that was investigated was very large and middle-American (over 22,000, children of participants in the Nurses’ Health Study II), and the subjects were scattered all over the U.S., so the affected children were subject to pollution that was measurably high in local areas but not especially unusual. Other studies have found autism rates to be twice as high as average near freeways.(2)
To get an idea of how concentrated pollutants become in human milk, note the following, which is all taken from authoritative sources, as indicated in the footnotes:
-- dioxins are typically present in human milk in concentrations exceeding the EPA’s Reference Dose (estimated reasonably safe dose, or RfD) by scores to hundreds of times;3
-- PBDEs are present in breast milk in concentrations normally well above and sometimes up to 40 times the EPA’s RfD;4 and
-- PCBs are normally present in human milk in concentrations about 20 times the maximum allowed by law in U.S. public water supplies.5
-- Mercury is present in human milk typically at levels eight times the WHO guideline for drinking-water quality;6 concentrations in infants were found in an authoritative study to be three times as high in infants breastfed for one year as in bottle-fed infants, with compatible findings in two other studies.7
All four of the above developmental toxins are present in infant formula in concentrations no more than 4% as high on average, and usually less than 1% as high, as their concentrations in human milk.8
And, not surprisingly, those high levels of developmental toxins ingested by infants have effects. One study found greatly increased rates of learning disability and attention deficit disorder (two and three times as high) among 12-to-15-year-olds with higher (approx. top 30%) levels of dioxins.8a This should be seen together with the authoritative evidence indicating that accumulated exposure to dioxins (called “persistent” for good reason) would still be twice as high among ten-year-old children breastfed for six or more months as among non-breastfed ten-year-olds;9 it is reasonable to consider the main determinant of the increased levels of dioxins (and therefore of their apparent harmful effects) in the 12-15-year-olds to have been breastfeeding. (Note that the concentration of dioxins discussed here was common.)
A large team of German scientists and doctors, studying 171 healthy mother-infant pairs, found "negative associations between (human) milk PCB and mental/motor development ... at all ages, becoming significant from 30 months onwards." Also, "negative associations with PCB increased with age." They found no significant association of the children’s neurological development with PCB levels in umbilical cord blood, whereas they did find association with breast milk PCB concentrations and duration.10
A Spanish study assessed PBDE levels in mothers and found that gestational exposure had no significant adverse effect on 4-year-olds, but exposure to those same mothers' PBDE levels via breastfeeding did have a substantial effect, including an 80% increase in relative risk of attention-deficit problems and a 160% increased relative risk of poor social competence.11 (“Poor social competence” is a way of describing typical characteristics of people with the autism spectrum of disorders, or ASD.) Note that this study was carried out in Europe, where PBDE levels are known to be one-tenth (or less) as high as in the United States.11a
At least six published studies have found high levels of mercury in those diagnosed with autism.12
As a kind of summary, note the statement by two leading experts on developmental toxins (Grandjean and Landrigan) who said, “Persistent lipophilic substances, including specific pesticides and halogenated industrial compounds, such as PCBs, accumulate in maternal adipose tissue and 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.13
To read more about environmental pollutants and about possible effects on infants after the pollutants have become concentrated into human milk, see www.pollutionaction.org/breastfeeding-and-autism-and-cancer.htm
There is a very large amount of published scientific information from authoritative sources concerning the toxins that are known to be substantially present in breast milk, including their known and probable effects and their sources in the environment. One can read a summary of much of that information at www.breastfeeding-vs-formula.info. However, even that summarized presentation about the toxins is over 30 pages long; a 3-page article that is just a brief summary of apparent effects of those pollutants in breast milk can be found at www.breastfeeding-effects.info.
Obviously, a great deal can be said and has been said about the presumed benefits of breastfeeding, so it may be difficult for a mother to decide whether or not to breastfeed her infant. The most authoritative statement of the benefits of breastfeeding can be found in the U.S. “Surgeon General’s Call to Action to Support Breastfeeding 2011.”14 But that statement tells one side of a story that has two important sides. The Surgeon General acknowledges that the claims about breastfeeding’s benefits are based on studies of a type (“observational” -- see p. 33 of her Call to Action) that the U.S. Agency for Healthcare Research and Quality considers to be subject to false conclusion.15 Studies of that type would find high death rates in Florida to be associated with sunshine, while typically not properly dealing with confounders, such as the advanced ages of many Florida residents. There are many reasons to look with skepticism at those claims of benefits, only one of which is that there are over 50 scientific studies that have found breastfeeding to have adverse health effects (see www.breastfeeding-studies.info).
A rational consideration of this often-emotional issue is greatly aided by the fact that breastfeeding rates greatly increased in the U.S. during the 1970’s, so that there is now an extensive historical record that enables us to see what actually happened after breastfeeding increased. The health data for the recent decades (mainly as provided by the CDC) shows that, of all the childhood diseases that are claimed to be reduced by breastfeeding, all but one instead actually increased substantially after breastfeeding rates increased. (see www.breastfeedingprosandcons.info) Regarding the only one that did not increase, neither did it decline as should have been expected if the claims about breastfeeding’s benefits had been valid. (see www.breastfeeding-and-sids.info)
In some parts of less-developed countries, the problems could be even greater than in developed countries, since some of the most potent developmental toxins (such as DDT, leaded gasoline, and PCBs) have been outlawed or severely curtailed in most developed countries but not in many other countries of the world. Environmental regulations in many developed countries have successfully reduced emissions of some toxins (such as dioxins and diesel emissions) from some major sources, whereas equivalent polluters (especially industrial sources, gold-mining activities that emit mercury, etc.) in less-developed countries continue unabated in many cases.
(a) “More than 350 pollutants found in breast milk,” Geoffrey Lean Environment Correspondent Sunday 11 July 1999 at www.independent.co.uk/news/more-than-350-pollutants-found-in-breast-milk-1105582.html
(1) Perinatal Air Pollutant Exposures and Autism Spectrum Disorder in the Children of Nurses’ Health Study II Participants, Roberts et al., published June, 2013 in Environmental Health Perspectives, at ehp.niehs.nih.gov/1206187
(2) "Residential Proximity to Freeways and Autism in the CHARGE Study" , Environmental Health Perspectives, Published in 119(6) Jun 2011, Heather E. Volk, Irva Hertz-Picciotto et al., reported in ScienceDaily (Dec. 17, 2010), "Proximity to Freeway Associated With Autism"
(3) Re: EPA’s RfD for dioxin: At www.epa.gov/iris/supdocs/dioxinv1sup.pdf in section 4.3.5, at end of that section, "...the resulting RfD in standard units is 7 × 10−10 mg/kg-day." (that is, O.7 pg of TEQ/kg-d)
Re: breastfed infants’ exposures to dioxins, in U.S. and internationally:
- Infant Exposure to Dioxin-like Compounds in Breast Milk Lorber (Senior Scientist at EPA) et al., VOL. 110 No. 6 June 2002, Environmental Health Perspectives at http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=54708#Download
- Focant et al., Levels of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and polychlorinated biphenyls in human milk from different regions of France, Science of The Total Environment, Volumes 452–453, 1 May 2013, Pages 155–162 abstract at http://www.sciencedirect.com/science/article/pii/S0048969713002404
- Yang J, et al., PCDDs, PCDFs, and PCBs concentrations in breast milk from two areas in Korea: body burden of mothers and implications for feeding infants. Chemosphere. 2002 Jan;46(3):419-28. At www.ncbi.nlm.nih.gov/pubmed/11829398
- Bencko V et al., Exposure of breast-fed children in the Czech Republic to PCDDs, PCDFs, and dioxin-like PCBs. Environ Toxicol Pharmacol. 2004 Nov;18(2):83-90. Abstract at http://www.ncbi.nlm.nih.gov/pubmed/21782737/
- Nakatani T, et al., Polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, and coplanar polychlorinated biphenyls in human milk in Osaka City, Japan Arch Environ Contam Toxicol. 2005 Jul;49(1):131-40. Epub 2005 Jun 22. Found at http://www.ncbi.nlm.nih.gov/pubmed/15983863
- Deng B, et al., Levels and profiles of PCDD/Fs, PCBs in mothers' milk in Shenzhen of China: estimation of breast-fed infants' intakes.Environ Int. 2012 Jul;42:47-52.. At www.ncbi.nlm.nih.gov/pubmed/21531025
- Chovancová J, et al., PCDD, PCDF, PCB and PBDE concentrations in breast milk of mothers residing in selected areas of Slovakia Chemosphere. 2011 May;83(10):1383-90. doi: 10.1016/j. At www.ncbi.nlm.nih.gov/pubmed/21474162
- J Grigg, Environmental toxins; their impact on children’s health, Arch Dis Child 2004;89:244-250 doi:10.1136/adc.2002.022202 at http://adc.bmj.com/content/89/3/244.full
-Table 5-4 of EPA (2010) An exposure assessment of polybrominated diphenyl ethers. National Center for Environmental Assessment, Washington, DC; EPA/600/R-08/086F. http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=210404, Schechter study in first page of table. Also Section 5.6.2, near end of section, of above.
- Costa et al.,Developmental Neurotoxicity Of Polybrominated Diphenyl Ether (PBDE) Flame Retardants, Neurotoxicology. 2007 November; 28(6): 1047–1067. PMCID: PMC2118052 NIHMSID:
- EPA Technical Fact Sheet on Polybrominitated Diphenyl Eithers (PBDEs) and PBBs, p.3 at www.epa.gov/fedfac/pdf/technical_fact_sheet_pbde_pbb.pdf Regarding prevalence of tetraBDEs, see Costa LG, et al., Polybrominated diphenyl ether (PBDE) flame retardants: environmental contamination, human body burden and potential adverse health effects. Acta Biomed. 2008 Dec;79(3):172-83 at www.ncbi.nlm.nih.gov/pubmed/19260376.
(5) U.S. Agency for Toxic Substances and Disease Registry, Toxicological Profile for Polychlorinated Biphenyls (PCBs), 2000, at http://www.atsdr.cdc.gov/toxprofiles/tp17.pdf This ATSDR report quotes a range of concentrations of PCBs in human milk as from 238 to 271 ng/g lipid weight. 1 g lipid weight = about 25g whole weight (assuming 4% fat in human milk). So the concentrations found in the studies were about 250 ng/25g whole weight, which = 10ng/g whole weight. 1 g (gram) = 1 ml of water., so the 10 ng/g whole weight is the same as 10ng/ml. That is the same as 10,000 ng per liter, which is the same as .01 mg/liter. So the levels of PCBs in human milk seem to be about .01 mg/liter, compared with .0005 mg/liter, the maximum allowed by law in U.S. public water systems. That is, about 20 times the concentration that would be allowed in public water systems.
(6) typical 8 parts per billion in breast milk, according to U.S. ATSDR document on mercury at http://www.atsdr.cdc.gov/toxprofiles/tp46-c5.pdf, p. 443, which compares with1 microgram per liter (1 microgram per billion micrograms), or 1 part per billion, the WHO guideline value for drinking water: (WHO, Mercury in Drinking-water Background document for development of WHO Guidelines for Drinking-water Quality WHO/SDE/WSH/03.04/10 at http://www.who.int/water_sanitation_health/dwq/chemicals/en/mercury.pdf p. 8 Accessed 4/8/2014)
(7) P. Grandjean et al., Human Milk as a Source of Methylmercury Exposure in Infants, Environmental Health Perspectives, accepted Oct. 1993 www.ncbi.nlm.nih.gov/pmc/articles/PMC1567218/pdf with compatible results found in other studies: Marques RC, et al., Hair mercury in breast-fed infants exposed to thimerosal-preserved vaccines. Eur J Pediatr. 2007 Sep;166(9):935-41 at www.sarnet.org/lib/VaxHgBrazil1.pdf; the authors found that, during 6 months of breastfeedinging, infants' hair-Hg increased 446%, 40% of which was from vaccinations. Also Exploration Of Perinatal Pharmacokinetic Issues Contract No. 68-C-99-238, Task Order No. 13 Prepared for: Office of Research and Development, U.S. Environmental Protection Agency Prepared by: Versar, Inc. EPA/630/R-01/004 Section 184.108.40.206, at www.epa.gov/raf/publications/pdfs/PPKFINAL.PDF
- Re dioxins in breast milk, see footnote 26 above.
- Re dioxins in formula: U.K. Food Standards Agency Food Survey Information Sheet 49/04 MARCH 2004, Dioxins and Dioxin-Like PCBs in Infant Formulae, found at http://www.food.gov.uk/multimedia/pdfs/fsis4904dioxinsinfantformula.pdf
- Compatible figures were found in Weijs PJ, et al., Dioxin and dioxin-like PCB exposure of non-breastfed Dutch infants. Chemosphere. 2006 Aug;64(9):1521-5. Epub 2006 Jan 25 at www.ncbi.nlm.nih.gov/pubmed/16442144
Re: PBDEs in formula about 3% of concentration in breast milk:
- Re PBDEs in breast milk, 1,056 pg/g wet weight: Schecter et al., Polybrominated Diphenyl Ether (PBDE) Levels in an Expanded Market Basket Survey of U.S. Food and Estimated PBDE Dietary Intake by Age and Sex, Environ Health Perspect. Oct 2006; 114(10): 1515–1520, 4th paragraph from end, at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1626425 This study was cited in the EPA document below, Section 5.6.2, 2nd paragraph.
- In formula: Section 4.7 , p. 4-77, 2nd paragraph (citing Schechter et al., finding of 25 and 32 pg/g wwt, ) of U.S. EPA (2010) An exposure assessment of polybrominated diphenyl ethers. http:/cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=210404
Re: Mercury in formula less than 1% as high as in human milk:
- See footnote 7 above re mercury in breast milk.
- Food Additives & Contaminants: Part B: Surveillance Volume 5, Issue 1, 2012 Robert W. Dabeka et al., Survey of total mercury in infant formulae and oral electrolytes sold in Canada DOI: 10.1080/19393210.2012.658087 at
Re: PCBs in infant formula typically less than 1% but up to about 4% as high as in human milk:
- In breast milk: About 250 ng/g lipid weight. In soy-based formula: about 10 ng/g lipid weight. U.S. Agency for Toxic Substances and Disease Registry, Toxicological Profile for Polychlorinated Biphenyls (PCBs), 2000, pp. 560, 573, at http://www.atsdr.cdc.gov/toxprofiles/tp17.pdf Data does not appear to be available for PCBs in cow’s-milk-based infant formula, but data for whole milk could give an approximation, as follows: adding together the figures for the two kinds of PCBs in this study provides a range of 52 to 2455 ng/kg fat, which equals .05 to 2.45 ng/g fat (lipid) (Krokos et al., Levels of selected ortho and non-ortho polychlorinated biphenyls in UK retail milk, Chemosphere. 1996 Feb;32(4):667-73. at www.ncbi.nlm.nih.gov/pubmed/8867147)
8a) Lee et al., Association of serum concentrations of persistent organic pollutants with the prevalence of learning disability and attention deficit disorder, J Epidemiol Community Health 2007;61:591–596. doi: 10.1136/jech.2006.054700 at http://jech.bmj.com/content/61/7/591.full.pdf+html.
(9) Lorber et al., Infant Exposure to Dioxin-like Compounds in Breast Milk, Volume 110 | Number 6 | June 2002 • Environmental Health Perspectives (a peer-reviewed journal published by the National Institute of Environmental Health Sciences of NIH) http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=54708#Download
(10) (Walkowiak et al., Environmental exposure to polychlorinated biphenyls and quality of the home environment: effects on psychodevelopment in early childhood. Lancet 2001: 358: 1602-07 Abstract at www.thelancet.com/journals/lancet/article/PIIS0140-6736(01)06654-5/abstract)
(11) Gascon M. et al., Effects of pre and postnatal exposure to low levels of polybromodiphenyl ethers on neurodevelopment and thyroid hormone levels at 4 years of age Environ Int. 2011 Apr;37(3):605-11. doi: 10.1016/j.envint.2010.12.005. Epub 2011 Jan 14 found at www.ncbi.nlm.nih.gov/pubmed/21237513)
(11a) Giordano et al., Developmental Neurotoxicity: Some Old and New Issues, ISRN Toxicol. 2012; 2012: 814795, PMCID: PMC3658697 at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3658697
(12) See footnotes 6, 15, 16, and 29 in D. Austin, An epidemiological analysis of the ‘autism as mercury poisoning’ hypothesis’, International Journal of Risk and Safety in Medicine, 20 (2008) 135-142 at http://researchbank.swinburne.edu.au/vital/access/manager/Repository/swin:9302
Also Adams JB et al., Biol Trace Elem Res. 2013 Feb;151(2):171-80. doi: 10.1007/s12011-012-9551-1. Epub 2012 Nov 29.Toxicological status of children with autism vs. neurotypical children and the association with autism severity. at http://www.ncbi.nlm.nih.gov/pubmed/23192845
Also Geier DA et al., Blood mercury levels in autism spectrum disorder: Is there a threshold level? Acta Neurobiol Exp (Wars). 2010;70(2):177-86, http://www.ncbi.nlm.nih.gov/pubmed/20628441
(13) Grandjean P, Landrigan PJ. Developmental neurotoxicity of industrial chemicals. Lancet. 2006;368:2167–2178. at http://www.reach-compliance.eu/english/documents/studies/neurotoxity/PGrandjean-PjLandrigan.pdf p. 2
(15) Agency for Healthcare Research and Quality, U.S. DHHS, Systems to Rate the Strength of Scientific Evidence, Evidence Report/Technology Assessment: Number 47 archive.ahrq.gov/clinic/epcsums/strengthsum.pdf
Also: Jensen, A.A. et al, Chemical Contaminants in Human Milk, CRC Press, Inc., Boca Raton, Ann Arbor, Boston, 1991, p 15. 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
*For information about Pollution Action and to read a number of other articles dealing with effects of pollutants in human milk, go to www.pollutionaction.org