Methodology for characterizing distributions of incremental body burdens of 2,3,7,8-TCDD and DDE from breast milk in North American nursing infants

Environmental Chemicals in Breast Milk and Formula: Exposure and Risk Assessment Implications

BACKGROUND

Human health risk assessment methods have advanced in recent years to more accurately estimate risks associated with exposure during childhood. However, predicting risks related to infant exposures to environmental chemicals in breast milk and formula remains challenging.

OBJECTIVES

Our goal was to compile available information on infant exposures to environmental chemicals in breast milk and formula, describe methods to characterize infant exposure and potential for health risk in the context of a risk assessment, and identify research needed to improve risk analyses based on this type of exposure and health risk information.

METHODS

We reviewed recent literature on levels of environmental chemicals in breast milk and formula, with a focus on data from the United States. We then selected three example publications that quantified infant exposure using breast milk or formula chemical concentrations and estimated breast milk or formula intake. The potential for health risk from these dietary exposures was then characterized by comparison with available health risk benchmarks. We identified areas of this approach in need of improvement to better characterize the potential for infant health risk from this critical exposure pathway.

DISCUSSION

Measurements of chemicals in breast milk and formula are integral to the evaluation of risk from early life dietary exposures to environmental chemicals. Risk assessments may also be informed by research investigating the impact of chemical exposure on developmental processes known to be active, and subject to disruption, during infancy, and by analysis of exposure-response data specific to the infant life stage. Critical data gaps exist in all of these areas.

CONCLUSIONS

Better-designed studies are needed to characterize infant exposures to environmental chemicals in breast milk and infant formula as well as to improve risk assessments of chemicals found in both foods. https://doi.org/10.1289/EHP1953.

Infant Dietary Exposures to Environmental Chemicals and Infant/Child Health: A Critical Assessment of the Literature

BACKGROUND

The benefits of breastfeeding to the infant and mother have been well documented. It is also well known that breast milk contains environmental chemicals, and numerous epidemiological studies have explored relationships between background levels of chemicals in breast milk and health outcomes in infants and children.

OBJECTIVES

In this paper, we examine epidemiological literature to address the following question: Are infant exposures to background levels of environmental chemicals in breast milk and formula associated with adverse health effects? We critically review this literature a) to explore whether exposure-outcome associations are observed across studies, and b) to assess the literature quality.

METHODS

We reviewed literature identified from electronic literature searches. We explored whether exposure-outcome associations are observed across studies by assessing the quality (using a modified version of a previously published quality assessment tool), consistency, and strengths and weaknesses in the literature. The epidemiological literature included cohorts from several countries and examined infants/children either once or multiple times over weeks to years. Health outcomes included four broad categories: growth and maturation, morbidity, biomarkers, and neurodevelopment.

RESULTS

The available literature does not provide conclusive evidence of consistent or clinically relevant health consequences to infants exposed to environmental chemicals in breast milk at background levels.

CONCLUSIONS

It is clear that more research would better inform our understanding of the potential for health impacts from infant dietary exposures to environmental chemicals. A critical data gap is a lack of research on environmental chemicals in formula and infant/child health outcomes. https://doi.org/10.1289/EHP1954.

Use of a simple pharmacokinetic model to study the impact of breast-feeding on infant and toddler body burdens of PCB 153, BDE 47, and DDE

Several studies have examined the role of breast milk consumption in the buildup of environmental chemicals in infants, and have concluded that this pathway elevates infant body burdens above what would occur in a formula-only diet. Unique data from Australia provide an opportunity to study this finding using simple pharmacokinetic (PK) models. Pooled serum samples from infants in the general population provided data on PCB 153, BDE 47, and DDE at 6-month increments from birth until 4 years of age. General population breast-feeding scenarios for Australian conditions were crafted and input into a simple PK model which predicted infant serum concentrations over time. Comparison scenarios of background exposures to characterize formula-feeding were also crafted. It was found that the models were able to replicate the rise in measured infant body burdens for PCB 153 and DDE in the breast-feeding scenarios, while the background scenarios resulted in infant body burdens substantially below the measurements. The same was not true for BDE 47, however. Both the breast-feeding and background scenarios substantially underpredicted body burden measurements. Two possible explanations were offered: that exposure to higher BDE congeners would debrominate and form BDE 47 in the body, and/or, a second overlooked exposure pathway for PBDEs might be the cause of high infant and toddler body burdens. This pathway was inhalation due to the use of PBDEs as flame retardants in bedding materials. More research to better understand and quantify this pathway, or other unknown pathways, to describe infant and toddler exposures to PBDEs is needed.

Levels of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and polychlorinated biphenyls in human milk from different regions of France

We report on the pilot study carried out before the start of the Elfe project (French longitudinal study from childhood). A total of 44 samples of mature human milk were collected at home 8 weeks after delivery. A total of 7 polychlorinated dibenzo-p-dioxins (PCDDs), 10 polychlorinated dibenzofurans (PCDFs), 12 dioxin-like (DL) polychlorinated biphenyls (PCBs), and 6 non dioxin-like (NDL)-PCBs were measured. For total TEQ (PCDD/Fs and DL-PCBs), the geometric mean concentration was 17.81 pg TEQ(WHO05)/g lipids. Relative PCDD, PCDF, and DL-PCB contributions to the arithmetic mean TEQ(WHO05) were 38%, 18%, and 44%, respectively. The use of TEF(WHO05) instead of TEF(WHO98) resulted in a 27% reduction of the total TEQ value. Although PCDD levels did not significantly change (less than 0.5% increase), PCDF and DL-PCB levels both decreased by 35% and 38%, respectively. Levels have been compared to data obtained during a previous non-reported national study conducted in 1998 (TEF(WHO98)) in French lactaria (n=244). The mean of PCDD/Fs has decreased about 39.4% (18.8 pg TEQ(WHO98)/g lipids in 1998 vs 11.4 pg TEQ(WHO98)/g lipids in pilot study), respectively 41.5% for PCDDs (10.6 pg TEQ(WHO98)/g lipids in 1998 vs 6.2 pg TEQ(WHO98)/g lipids in pilot study) and 36.7% for PCDFs (7.9 pg TEQ(WHO98)/g lipids in 1998 vs 5.0 pg TEQ(WHO98)/g lipids in pilot study). For the sum of the 6 NDL-PCBs, the 2007 geometric mean concentration in milk was 176.3 ng/g lipids. The arithmetic mean lipid concentration in 2007 breast milk was 26.4 g/l (range from 6.0 to 46.7 g/l). A PCDD/F and DL-PCB daily intake was estimated to be 62.3 pg TEQ(WHO05)/kg body weight per day (85.0 pg TEQ(WHO98)/kg body weight per day) for a baby of 5 kg of body weight fed daily with 700 ml of maternal milk containing 25 g/l of lipids.

Pesticide exposure in children

Pesticides are a collective term for a wide array of chemicals intended to kill unwanted insects, plants, molds, and rodents. Food, water, and treatment in the home, yard, and school are all potential sources of children's exposure. Exposures to pesticides may be overt or subacute, and effects range from acute to chronic toxicity. In 2008, pesticides were the ninth most common substance reported to poison control centers, and approximately 45% of all reports of pesticide poisoning were for children. Organophosphate and carbamate poisoning are perhaps the most widely known acute poisoning syndromes, can be diagnosed by depressed red blood cell cholinesterase levels, and have available antidotal therapy. However, numerous other pesticides that may cause acute toxicity, such as pyrethroid and neonicotinoid insecticides, herbicides, fungicides, and rodenticides, also have specific toxic effects; recognition of these effects may help identify acute exposures. Evidence is increasingly emerging about chronic health implications from both acute and chronic exposure. A growing body of epidemiological evidence demonstrates associations between parental use of pesticides, particularly insecticides, with acute lymphocytic leukemia and brain tumors. Prenatal, household, and occupational exposures (maternal and paternal) appear to be the largest risks. Prospective cohort studies link early-life exposure to organophosphates and organochlorine pesticides (primarily DDT) with adverse effects on neurodevelopment and behavior. Among the findings associated with increased pesticide levels are poorer mental development by using the Bayley index and increased scores on measures assessing pervasive developmental disorder, inattention, and attention-deficit/hyperactivity disorder. Related animal toxicology studies provide supportive biological plausibility for these findings. Additional data suggest that there may also be an association between parental pesticide use and adverse birth outcomes including physical birth defects, low birth weight, and fetal death, although the data are less robust than for cancer and neurodevelopmental effects. Children's exposures to pesticides should be limited as much as possible.

Estimation of human body concentrations of DDT from indoor residual spraying for malaria control

Inhabitants of dwellings treated with DDT for indoor residual spraying show high DDT levels in blood and breast milk. This is of concern since mothers transfer lipid-soluble contaminants such as DDT via breastfeeding to their children. Focusing on DDT use in South Africa, we employ a pharmacokinetic model to estimate DDT levels in human lipid tissue over the lifetime of an individual to determine the amount of DDT transferred to children during breastfeeding, and to identify the dominant DDT uptake routes. In particular, the effects of breastfeeding duration, parity, and mother's age on DDT concentrations of mother and infant are investigated. Model results show that primiparous mothers have greater DDT concentrations than multiparous mothers, which causes higher DDT exposure of first-born children. DDT in the body mainly originates from diet. Generally, our modeled DDT levels reproduce levels found in South African biomonitoring data within a factor of 3.

Assessment of exposure to PCB 153 from breast feeding and normal food intake in individual children using a system approach model

Investigators have typically relied on a single or few discrete time points as measures of polychlorinated biphenyl (PCB) body burden, however health effects are more likely to be the result of integrative exposure in time, optionally expressed as an area under the time curve (AUC) of PCB serum concentration. Using data from a subgroup of 93 infants from a birth cohort in eastern Slovakia-a region highly polluted by PCBs-we fit a system type model, customized to our longitudinal measures of serum PCB concentrations in cord, 6, 16, and 45 month blood specimens. The most abundant congener, PCB 153, was chosen for modeling purposes. In addition to currently used methods of exposure assessment, our approach estimates a concentration time profile for each subject, taking into account mean residence time of PCB 153 molecules in the body, duration of breast feeding, hypothetical PCB 153 concentration in steady-state without breast feeding and alternately without normal food intake. Hypothetical PCB 153 concentration in steady-state without normal food intake correlates with AUC (r=0.84, p<0.001) as well as with duration of breast feeding (r=0.64, p<0.001). It makes possible to determine each subject's exposure profile expressed as AUC of PCBs serum concentration with a minimum model parameters. PCB body burden in most infants was strongly associated with duration of breast feeding in most, but not all children, was apparent from model output.

POP levels in breast milk and maternal serum and thyroid hormone levels in mother-child pairs from Uppsala, Sweden

In experimental studies, it has frequently been observed that the homeostasis of thyroid hormones (THs) is affected by exposure to persistent organic pollutants (POPs), such as dioxins and PCBs. In man, similar effects have been indicated in several epidemiological studies. In order to investigate the possible effect on THs at low background exposures found among the Swedish population the following study was performed. Primiparous women (n=395) in the Uppsala region were recruited between 1996 and 1999. Of these, 325 mothers agreed to donate a serum sample in late pregnancy and breast milk was obtained from 211 women 3 weeks after delivery. Babies were sampled for blood at 3 weeks (n=150) and 3 months (n=115) after birth. In connection to the sampling, questions on personal characteristics were asked. Levels of low (tri- to penta-) chlorinated PCB, di-ortho PCB, p,p'-DDE, (mono-ortho) PCB TEQ and PCDD/DF TEQ were monitored in breast milk and in mother's blood (not PCDD/DF). The results showed that the measured TH levels (thyroid-stimulating hormone - TSH, total tri-iodothyronine - TT3, free thyroxine - FT4) in mothers and children were within the reference range. Some significant associations were seen between POP exposures and TH levels in mother or child after simple regression analysis. Following adjustment for important confounding factors, the significant associations mostly disappeared. However, significantly decreasing TT3 levels with increasing prenatal low-chlorinated PCB exposure were still seen in 3 week old children, and on TT3 in mothers exposed to PCDD/DF. In conclusion, the study clearly shows the importance of adjustment for important confounding factors in the analysis of possible associations between POP exposure and hormonal effects. The remaining associations are weak in both children and mothers and the clinical consequences of these alterations are uncertain. When comparing studies that investigate associations between TH levels and POP levels during the perinatal stage, no obvious between-study concordance was seen regarding the critical dose for hormonal effects to occur.

Do human milk concentrations of persistent organic chemicals really decline during lactation? Chemical concentrations during lactation and milk/serum partitioning

BACKGROUND

Conventional wisdom regarding exposures to persistent organic chemicals via breast-feeding assumes that concentrations decline over the course of lactation and that the mother's body burden reflects her cumulative lifetime exposure. Two important implications stemming from these lines of thought are, first, that assessments of early childhood exposures should incorporate decreasing breast milk concentrations over lactation; and, second, that there is little a breast-feeding mother can do to reduce her infant's exposures via breast-feeding because of the cumulative nature of these chemicals.

OBJECTIVES

We examined rates of elimination and milk/serum partition coefficients for several groups of persistent organic chemicals.

METHODS

We collected simultaneous milk and blood samples of 10 women at two times postpartum and additional milk samples without matching blood samples.

RESULTS

Contrary to earlier research, we found that lipid-adjusted concentrations of polybrominated diphenyl ethers, polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins and furans, and organochlorine pesticides in serum and milk do not consistently decrease during lactation and can increase for some women. Published research has also suggested an approximate 1:1 milk/serum relationship (lipid adjusted) on a population basis for 2,3,7,8-tetrachlorodibenzo-p-dioxin; however, our results suggest a more complex relationship for persistent, lipophilic chemicals with the milk/serum relationship dependent on chemical class.

CONCLUSIONS

Decreases in concentration of lipophilic chemicals on a lipid-adjusted basis during lactation should no longer be assumed. Thus, the concept of pumping and discarding early milk as means of reducing infant exposure is not supported. The hypothesis that persistent lipophilic chemicals, on a lipid-adjusted basis, have consistent concentrations across matrices is likely too simplistic.

A physiologically based pharmacokinetic model for the assessment of infant exposure to persistent organic pollutants in epidemiologic studies

BACKGROUND

It has been suggested that pre- and postnatal exposure to persistent organic pollutants (POPs) can promote several adverse effects in children, such as altered neurodevelopment. Epidemiologic studies to date have relied on the analysis of biological samples drawn pre- or post-natally for exposure assessment, an approach that might not capture some key events in the toxicokinetics of POPs.

OBJECTIVES

We aimed to build a generic physiologically based pharmacokinetic (PBPK) modeling framework for neutral POPs to assess infant toxicokinetic profiles and to validate the model using data on POP levels measured in mothers and infants from a Northern Québec Inuit population.

METHODS

The PBPK model developed herein was based upon a previously published model to which an infant submodel was added. Using the model and maternal blood levels at the time of delivery, exposure to 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (p,p'-DDE), 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (p,p'-DDT), hexachlorobenzene (HCB), beta-hexachlorocyclohexane (beta-HCH), 2,2',3,4,4',5'-hexachlorobiphenyl (PCB-138), 2,2',4,4',5,5'-hexachlorobiphenyl (PCB-153), and 2,2',3,4,4',5,5'-heptachlorobiphenyl (PCB-180) in mothers was estimated to subsequently simulate infant blood, breast milk, and cord blood POP concentration. Simulations were then compared with corresponding measured levels through Spearman correlation analyses.

RESULTS

Predictions were highly correlated with measured concentrations for PCB-153, PCB-180, PCB-138, HCB, and p,p'-DDE (r = 0.83-0.96). Weaker correlations were observed for p,p'-DDT and beta-HCH for which levels were near the limits of detection.

CONCLUSION

This is the first study to validate a PBPK model of POPs in infants on an individual basis. This approach will reduce sampling efforts and enable the use of individualized POP toxicokinetic profiles in the epidemiologic studies of POP adverse effects on child development.

Immune cell counts and risks of respiratory infections among infants exposed pre- and postnatally to organochlorine compounds: a prospective study

BACKGROUND

Early-life chemical exposure may influence immune system development, subsequently affecting child health. We investigated immunomodulatory potentials of polychlorinated biphenyls (PCBs) and p,p'-DDE in infants.

METHODS

Prenatal exposure to PCBs and p,p'-DDE was estimated from maternal serum concentrations during pregnancy. Postnatal exposure was calculated from concentrations of the compounds in mother's milk, total number of nursing days, and percentage of full nursing each week during the 3 month nursing period. Number and types of infections among infants were registered by the mothers (N = 190). White blood cell counts (N = 86) and lymphocyte subsets (N = 52) were analyzed in a subgroup of infants at 3 months of age.

RESULTS

Infants with the highest prenatal exposure to PCB congeners CB-28, CB-52 and CB-101 had an increased risk of respiratory infection during the study period. In contrast, the infection odds ratios (ORs) were highest among infants with the lowest prenatal mono-ortho PCB (CB-105, CB-118, CB-156, CB-167) and di-ortho PCB (CB-138, CB-153, CB-180) exposure, and postnatal mono- and di-ortho PCB, and p,p'-DDE exposure. Similar results were found for pre- and postnatal CB-153 exposure, a good marker for total PCB exposure. Altogether, a negative relationship was indicated between infections and total organochlorine compound exposure during the whole pre- and postnatal period. Prenatal exposure to CB-28, CB-52 and CB-101 was positively associated with numbers of lymphocytes and monocytes in infants 3 months after delivery. Prenatal exposure to p,p'-DDE was negatively associated with the percentage of eosinophils. No significant associations were found between PCB and p,p'-DDE exposure and numbers/percentages of lymphocyte subsets, after adjustment for potential confounders.

CONCLUSION

This hypothesis generating study suggests that background exposure to PCBs and p,p'-DDE early in life modulate immune system development. Strong correlations between mono- and di-ortho PCBs, and p,p'-DDE exposures make it difficult to identify the most important contributor to the suggested immunomodulation, and to separate effects due to pre- and postnatal exposure. The suggested PCB and p,p'-DDE modulation of infection risks may have consequences for the health development during childhood, since respiratory infections early in life may be risk factors for asthma and middle ear infections.

The heart of the matter on breastmilk and environmental chemicals: essential points for healthcare providers and new parents

Abstract The increasing number of environmental chemicals measured in breastmilk is a consequence of improved analytical capabilities and the increased interest in biomonitoring. It has been generally concluded that the benefits to the infant from breastfeeding outweigh potential risks associated with environmental chemical exposures associated with breastfeeding. However, there have been reports of subtle effects on infants associated with chemicals in breastmilk. Associations between concentrations of chemicals in breastmilk and a biochemical or other change in infants may signal the need for further study or regulatory action, whereas on an individual level, these changes may not be considered adverse. For healthcare providers, this distinction is critical, as many in the field are being asked for nuanced information on risks and benefits associated with breastfeeding, and this information is not readily available. Recognizing the challenge faced by healthcare providers, we have explored and developed a case study on dioxins in breastmilk. The essential conclusion for healthcare providers and new parents is that in studies of breastfed versus formula-fed infants across time, including times when levels of environmental chemicals such as dioxins were higher, beneficial effects associated with breastfeeding have been found. The current evidence does not support altering the World Health Organization recommendations promoting and supporting breastfeeding.

Perfluorinated compounds in human milk from Massachusetts, U.S.A

Perfluorinated compounds (PFCs), notably perfluorooctanesulfonate (PFOS) and perfluorooctanoic acid (PFOA), have been reported in human blood. Furthermore, the occurrence of PFCs in the blood of newborn babies, coupled with the need to study the potential association of PFC exposure with birth outcomes in neonates, suggests the need for determining the sources and magnitude of exposure in infants. In this study, nine PFCs were measured in 45 human breast milk samples collected in 2004 from Massachusetts, U.S.A. PFOS and PFOA were the predominant PFCs found at mean concentrations of 131 and 43.8 pg/mL, respectively. Comparison of the ratio of PFOS to PFOA in human milk with the ratios published for human serum from the U.S. female population suggested preferential partitioning of PFOA to milk. Concentrations of PFOA were significantly higher in the milk of mothers nursing for the first time (n = 34) than in the milk of mothers who have previously nursed (n = 8). Based on the estimated body weight and milk intake, the average and highest daily intakes of total PFCs by infants were 23.5 and 87.1 ng/kg bw, respectively. We found that the daily ingestion rates of PFOS and PFOA did not exceed the tolerable daily intake recommended by the U.K. Food Standards Agency. This is the first study to measure the occurrence of PFCs in human milk from the U.S.A.

Biomonitoring as a method for assessing exposure to perchlorate

Biomonitoring provides direct and quantitative information regarding human exposure to environmental toxicants, such as perchlorate (ClO(4)(-)). Because of concerns surrounding widespread exposure to ClO(4)(-), we are using biomonitoring methods to assess exposure to ClO(4)(-) and other physiologically relevant anions that can impact iodide uptake by the thyroid. These methods quantify ClO(4)(-), thiocyanate, nitrate, and iodide in human urine, milk, serum, blood spots, amniotic fluid, and infant formula using ion chromatography coupled with electrospray ionization tandem mass spectrometry. In this paper we summarize recent ClO(4)(-) biomonitoring research and provide three additional examples of the utility of biomonitoring for characterizing ClO(4)(-) exposure. Specifically, we examine variability in ClO(4)(-) excretion, compare the relative importance of different exposure sources in adults, and estimate ClO(4)(-) exposure in formula-fed infants. These applications provide examples of how biomonitoring can improve individual exposure assessment. Individual biomarker data can subsequently be compared with individual thyroid function data to better evaluate potential linkage between ClO(4)(-) exposure and health.

Polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in milk from Italian women living in Rome and Venice

The levels of selected polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) were measured in human milk samples from the areas of Venice and Rome, primarily in order to characterize the current levels of infant exposure to PCBs and PBDEs due to breast feeding in Italy. Sixteen non-dioxin-like PCBs, including the traditional indicator congeners, and 11 PBDEs, comprising the relevant PBDE-47, PBDE-99, and PBDE-153, were determined. Congeners were selected for analysis according to their relative abundance in human tissues, toxicological relevance, and diffusion in the environment. Dietary habits of the milk donors were recorded by questionnaires; mothers of the Venice area were classified into three groups according to their consumption of local fish, molluscs, and other fishery products. Sigma(16)(PCBs) and Sigma(11)(PBDEs) (ng g(-1) fat) for the areas of Venice and Rome were respectively, 250-390 and 240, and 1.6-2.8 and 4.1. An increase of fish and fishery product consumption could not be associated with an increase of PCB and PBDE levels in milk.

Persistent organic pollutants in human breast milk from Asian countries

In this paper, we concisely reviewed the contamination of persistent organic pollutants (POPs) such as polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), biphenyls (PCBs), dichlorodiphenyltrichloroethane and its metabolites (DDTs), hexachlorocyclohexane isomers (HCHs), chlordane compounds (CHLs), hexachlorobenzene (HCB) in human breast milk collected from Asian countries such as Japan, China, Philippines, Vietnam, Cambodia, India, Malaysia, and Indonesia during 1999-2003. Dioxins, PCBs, CHLs in Japanese, and DDTs in Vietnamese, Chinese, Cambodian, Malaysian, and HCHs in Chinese, Indian, and HCB in Chinese breast milk were predominant. In India, levels of dioxins and related compounds (DRCs) in the mothers living around the open dumping site were notably higher than those from the reference site and other Asian developing countries, indicating that significant pollution sources of DRCs are present in the dumping site of India and the residents there have been exposed to relatively higher levels of these contaminants possibly via bovine milk.

The aryl hydrocarbon receptor pathway and sexual differentiation of neuroendocrine functions

Historically, much of the research on health effects of environmental pollutants focused on ascertaining whether compounds were carcinogenic. More recent findings show that environmental contaminants also exert insidious effects by disrupting hormone action. Of particular concern are findings that developmental exposure to dioxins, chemicals that act through the aryl hydrocarbon receptor pathway, permanently alters sexually differentiated neural functions in animal models. In this review, we focus on mechanisms through which dioxins disrupt neuroendocrine development as exemplified by effects on a brain region critical for ovulation in rodents. We also provide evidence that dysregulation of GABAergic neural development may be a general mechanism underlying a broad spectrum of effects seen after perinatal dioxin exposure.

Elimination half-lives of selected polychlorinated dibenzodioxins and dibenzofurans in breast-fed human infants

Elimination half-life estimates for several polychlorinated dibenzodioxins/furans (PCDD/F) were calculated by modeling the blood and breast milk concentrations in two breast-fed human infants as reported by Abraham et al. (1996, 1998). Our analysis differs from that of other investigators in that we analyzed individual dioxin and furan congeners while the other studies considered TCDD only and we determined the half-lives in infants, rather than simply predicting body burdens in infants and older children. The average half-life values for each consistently measurable congener were determined to be less than about 6 mo and did not vary substantially between the two infants studied. The average elimination half-life values for 2,3,7,8-tetraCDD, 1,2,3,7,8-pentaCDD, 1,2,3,6,7,8-hexaCDD, 1,2,3,4,6,7,8-heptaCDD, and octaCDD were 0.40, 0.32, 0.39, 0.32, and 0.46 yr, respectively, and 0.27 yr for 2,3,4,7,8-pentaCDF. These values are in stark contrast with the 7 to 15+ yr values reported for these congeners in human adults (Michalek et al., 1996). These much shorter half-life values, likely attributable to rapid growth of the adipose tissue volume and enhanced fecal excretion of dioxins for breast-fed infants, explain why the much higher daily dioxin intake during breastfeeding does not translate to proportionately higher tissue concentrations. Thus, the shorter half-life of dioxins during breastfeeding needs to be considered when evaluating the dioxin hazard to children.

Estimates of exposures to perchlorate from consumption of human milk, dairy milk, and water, and comparison to current reference dose

To develop an enforceable drinking water standard from a health-based reference dose, sources of exposure and relevant exposure factors across the U.S. population must be considered. Human exposures, expressed as an estimated daily exposure, can be used to evaluate the health protectiveness of a range of potential regulatory values, thus providing a scientific foundation on which decisions can be based. Recent evidence points to detectable levels of perchlorate in milk and other foods. The purpose of this article is to estimate human exposure to perchlorate from ingestion of drinking water, human milk, and dairy milk. Drinking-water exposure was based on a range of possible regulatory values, derived from the recently established reference dose. Exposure to perchlorate from the consumption of milk was based on exploratory Food and Drug Administration dairy milk data, and on additional published perchlorate concentrations in dairy and human milk samples. This effort is exploratory in nature due to the limited data available at this time. However, it is anticipated that these exposure estimates and comparison with the current reference dose will stimulate dialogue and research that will advance the risk assessment for perchlorate.

Collection and use of exposure data from human milk biomonitoring in the United States

Human milk is a unique biological matrix that can be used to estimate exposures in both the mother and the breastfed infant. In addition, the presence of environmental chemicals in human milk may act as a sentinel for exposures to a broader population. Several factors play a role in determining the quantity of chemicals transferred to milk and, subsequently, to the breastfeeding infant, including maternal, infant, and chemical characteristics. Exposure to certain environmental chemicals during critical periods can disrupt normal infant development, yet few data exist to quantify the hazards posed by environmental chemicals in human milk. Chemicals measured in human milk may also provide insights to agents suspect in altering breast development and breast-related disease risk. Carefully designed exposure assessment and toxicokinetic studies are needed to elucidate mechanisms and establish relationships between human milk and other biologic matrices. Data from human milk biomonitoring studies can be used to inform and validate models that integrate information about chemical properties, human metabolism, and biomarker concentrations. Additional research is needed to determine the degree to which environmental chemicals enter, are present in, and are excreted from human milk, their impact on the host (mother), and the extent of their bioavailability to breastfeeding infants. This article describes how the collection and use of exposure data from human milk biomonitoring in the United States can be designed to inform future research and policy.

Biologic monitoring of exposure to environmental chemicals throughout the life stages: requirements and issues for consideration for the National Children's Study

Biomonitoring of exposure is a useful tool for assessing environmental exposures. The matrices available for analyses include blood, urine, breast milk, adipose tissue, and saliva, among others. The sampling can be staged to represent the particular time period of concern: preconceptionally from both parents, from a pregnant woman during each of the three trimesters, during and immediately after childbirth, from the mother postnatally, and from the child as it develops to 21 years of age. The appropriate sample for biomonitoring will depend upon matrix availability, the time period of concern for a particular exposure or health effect, and the different classes of environmental chemicals to be monitored. This article describes the matrices available for biomonitoring during the life stages being evaluated in the National Children's Study; the best biologic matrices for exposure assessment for each individual chemical class, including consideration of alternative matrices; the analytical methods used for analysis, including quality control procedures and less costly alternatives; the costs of analysis; optimal storage conditions; and chemical and matrix stability during long-term storage.

Induction of cell proliferation, micronuclei and hyperdiploidy/polyploidy in the mammary cells of DDT- and DMBA-treated pubertal rats

The environmental estrogen, dichlorodiphenyltrichloroethane (DDT), and its metabolites have been implicated in the development of breast cancer through mechanisms that remain to be elucidated. It has been hypothesized that exposure to DDT and its metabolites, during critical periods of development, can contribute to an elevated risk for breast cancer in adults. In the present study, we have investigated the effect of o,p'-DDT on mammary gland cell proliferation and chromosomal alterations, in a rat mammary cancer model (commonly used to study human cancer), to gain insights into its potential role in the development of breast cancer. Twenty-one-day-old female Sprague-Dawley (SD) rats were administered o,p'-DDT, 7,12-dimethylbenz[a]anthracene (DMBA), genistein, DDT+DMBA, or DDT+DMBA+genistein, over a 14-day period. To determine changes in chromosome number and structure, we used the micronucleus assay as well as multicolor fluorescence in situ hybridization (FISH) region-specific DNA probes for rat chromosomes 4 and 19. Cell proliferation was evaluated using 5-bromo-2'-deoxyuridine (BrdU). Significant increases in BrdU-incorporated cells were seen in the rats treated with DDT+DMBA. Although micronucleus frequencies were somewhat elevated in several of the treatment groups, significant increases were not seen in any of them. Significant increases in numerical chromosomal aberrations were detected in all of the DDT- and DMBA-treated groups. Genistein significantly reduced BrdU incorporation and polyploidy in the DDT+DMBA-treated rats. These initial studies indicate that DDT and DMBA can induce cellular and chromosomal alterations in the rat mammary gland, which is consistent with the hypothesis that these agents can induce early events in mammary carcinogenesis.

Human breast milk and xenoestrogen exposure: a possible impact on human health

Human milk is the best natural and optimal food for neonates with several immunologic, developmental and practical advantages throughout childhood. Although the World Health Organization strongly supports breastfeeding, it recognizes the potential health risks posed by the presence of environmental toxicants in breast milk. Contamination of human milk is widespread and due to decades of inadequately controlled pollution by toxicants, persistent pesticides or chemical solvents. These chemicals tend to degrade slowly in the environment, to bioaccumulate in the food chain and to have long half-lives in humans. Many of these environmental pollutants have estrogen-like activities and, thus they are called environmental estrogen disruptors or xenoestrogens. Certain adverse health and reproductive outcomes are attributed to these chemicals in laboratory animals and in wildlife as well as in humans. Here, we review available data from breast milk monitoring studies suggesting the environmental chemicals that may affect child health through breastfeeding.

Dioxin health risk to infants using simulated tissue concentrations

Dioxin concentrations in infant and child were simulated using physiologically based pharmacokinetic (PBPK) models developed for these groups. The infant model was validated by comparing the simulated concentration with the measured concentration from the literature, and they showed good agreement. Simulations with our PBPK model showed temporal patterns in concentrations in various tissues. For risk assessment, estimated concentrations of 29 dioxins in the liver were summed up in a toxic equivalency (TEQ) basis to be compared with actual 2,3,7,8-TCDD concentrations in rat liver associated with toxicity. Maximum liver concentrations in breast-fed and formula-fed infants were 16.8pg TEQ/g and 3.5pg TEQ/g, respectively. The level in breast-fed infant liver was approximately 1/300 of the level associated with hepatocellular carcinoma and 1/5 of the level found in maternal rat liver associated with alterations in reproductive organs in the next generation. Based on our analysis, the present contamination level is not safe enough, but further dose-response data is required for a quantitative risk assessment.

Pesticides and children

Prevention and control of damage to health, crops, and property by insects, fungi, and noxious weeds are the major goals of pesticide applications. As with use of any biologically active agent, pesticides have unwanted side-effects. In this review, we will examine the thesis that adverse pesticide effects are more likely to occur in children who are at special developmental and behavioral risk. Children's exposures to pesticides in the rural and urban settings and differences in their exposure patterns are discussed. The relative frequency of pesticide poisoning in children is examined. In this connection, most reported acute pesticide poisonings occur in children younger than age 5. The possible epidemiological relationships between parental pesticide use or exposure and the risk of adverse reproductive outcomes and childhood cancer are discussed. The level of consensus among these studies is examined. Current concerns regarding neurobehavioral toxicity and endocrine disruption in juxtaposition to the relative paucity of toxicant mechanism-based studies of children are explored.

Determination of polychlorinated dibenzo-p-dioxins and dibenzofurans and comparison of extraction methods for edible freshwater fish and frogs in South Korea by using a high-resolution GC/MS

Three different extraction methods were evaluated: Soxhlet extraction, accelerated solvent extractor extraction and alkali digestion with high-resolution gas chromatography/high-resolution mass spectrometry, for the analysis of edible freshwater fish and frogs. The recovery efficiencies for the different extraction methods were also compared. Using these extraction methods, the concentrations and spatial distributions of these compounds in freshwater fish and frogs (n = 99), collected from 31 locations on four major river systems (Han, Nakdong, Kum and Youngsan) and two wetlands in South Korea, were examined. The concentrations of total polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in all the freshwater fish and frog samples were analysed. The toxic equivalency (TEQ) concentration of PCDD/Fs in fish ranged from 0 (n.d.) to 1.309 pg I-TEQ g(-1) wet weight. Detailed concentrations for different types of fish were as follows (pg I-TEQ g(-1) wet weight): 0 (n.d.)-1.309 for crucian (mean 0.331, n = 28), 0.004-0.743 for carp (0.244, n = 10), 0.004-0.592 for dace (0.198, n = 8), 0.187-0.400 for cornet fish (0.287, n = 3), 0.164-0.410 for Korean piscivorous chub (0.303, n = 6), 0.105-0.516 for bass (0.310, n = 2), 0.451-0.812 for mullet (0.631, n = 2), 0.082 for long-nosed barbell, 0.100 for common Korean bitterling and 0.995 for dark chub. The total TEQ concentration ranged from 0 (n.d.) to 1.258 pg I-TEQ g(-1) wet weight for the two kinds of frogs (n = 36) investigated: 0 (n.d.)-1.258 pg I-TEQ g(-1) (mean 0.346, n = 29) for the bullfrog and from 0 (n.d.)-0.474 pg I-TEQ g(-1) (0.185, n = 7) for the mountain frog.

Children’s Behavior and Physiology and How It Affects Exposure to Environmental Contaminants

Infant, child, and adolescent exposures to environmental toxicants are different from those of adults because of differences in behavior and physiology. Because of these differences, there is the potential for quantitatively different exposures at various stages of development. Pediatricians are well aware of these behavioral and physiologic differences from a clinical standpoint—namely, food and water intake, soil ingestion, mouthing behavior, inhalation physiology, and activity level—as they relate to the ratio of these parameters between the adult and the child when considering weight and surface area. Pediatricians recognized the importance of pica as a cause of lead poisoning, the noxious effect of second-hand smoke, and the greater propensity for addiction during the adolescent years. For determining the differences in impact of many environmental toxicants between adults and children, research is needed to document where and whether these differences result in deleterious effects.

Possible range of dioxin concentration in human tissues: simulation with a physiologically based model

In risk evaluation of dioxins, monitoring chemical concentrations in human tissues is an important step, and these concentration data can be utilized along with animal toxicity data for extrapolation of human manifestation. However large differences in dioxin concentrations usually exist even among individuals who have never been accidentally exposed to high quantities of dioxin, and this may cause problems in risk analysis. Body size, age, and history of food consumption are factors responsible for these interindividual differences in addition to exposure levels. Using a physiologically based pharmacokinetic (PBPK) model, the influence of differences in body weight, gastrointestinal absorption, and half-life and intake of dioxin were examined on tissue chemical concentration. Dioxin concentrations over a 40-yr time course in human liver, kidneys, fat, blood, muscle and richly perfused tissue were simulated for polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (CoPCBs). Model parameters such as tissue-blood partition coefficients for CoPCBs were prepared, and sensitivity analysis was also performed on these parameters. The range of tissue concentrations was approximately 0.17 to 4.1 times the standard concentration, which was calculated using standard model parameters. The simulated ranges included more than 80% of the individual anatomical data for 2,3,7,8-tetrachlorodibenzo-p-dioxin, 1,2,3,7,-pentachlorodibenzo-p-dioxin, and 3,3',4,4',5-pentachlorobiphenyl in liver, fat, and blood. These results suggest that differences in body weight, gastrointestinal absorption, and food intake behavior may partially explain variation in tissue concentrations among individuals, and the possible interindividual uncertainty, which is approximately 24 for the general Japanese population.

Guidelines for collection of human milk samples for monitoring and research of environmental chemicals

This article addresses sample collection protocols for monitoring and research of environmental chemicals in human milk. The process of milk synthesis and secretion and variations in contents of constituents that may impact measurement of environmental chemicals are presented. Possible sources of variation include parity, stage of lactation, method of sampling, maternal nutritional status, and dietary intake. General principles regarding how and when to collect milk samples are provided. For any previously unstudied environmental chemical in milk, all sources of variance must be assessed before a meaningful sampling protocol can be devised.

Human milk surveillance and research of environmental chemicals: concepts for consideration in interpreting and presenting study results

This article describes issues related to the interpretation, presentation, and use of data from human milk surveillance and research studies. It is hoped that researchers conducting human milk studies in the future will consider these concepts when formulating study conclusions and presenting data. The key issues discussed are; (1) communication of information on human milk constituents to health care providers and the public; (2) complexities associated with assessing risks and benefits when comparing breast-feeding and formula-feeding; (3) use of human milk information for trends analysis and assessment of the efficacy of restrictions on use/release of chemicals in the environment; and (4) risk assessment and regulatory decision-making concepts regarding environmental chemicals in human milk. As researchers conduct surveillance and research involving human milk, it is of the utmost importance that the results of these studies are provided with information on risk and benefits that place the data in perspective, so that those involved in decision making regarding infant nutrition (e.g., expectant mothers, physicians, midwives, nurses, and lactation consultants) can appropriately interpret the research data.

Levels and profiles of PCDDs, PCDFs and cPCBs in Belgian breast milk. Estimation of infant intake

Congener-specific analyses of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and non-ortho (coplanar) polychlorinated biphenyls (cPCBs) were performed on 20 non-pooled breast milk samples collected in or close to an industrial area of Wallonia (Belgium). PCDD/F concentrations ranged between 16.0 and 52.1 pg TEQ/g fat, with a mean value of 29.4 pg TEQ/g fat. If coplanar PCBs (77, 126, 169) are included in TEQ calculations, levels ranged between 22.2 and 100.2 pg TEQ/g fat, with a mean value of 40.8 pg TEQ/g fat. It appears that 2,3,7,8-TCDD, 1,2,3,7,8-PeCDD, 2,3,4,7,8-PeCDF and PCB-126 account for more than 90% of the TEQ. Estimated PCDD/F dietary intake is 76 pg TEQ/kg body weight (bw)/day. This value is almost 20 times higher than the World Health Organization tolerable daily intake. A value of 103 pg TEQ/kg bw/day represents the intake of PCDDs, PCDFs and cPCBs (no mono-ortho PCBs included).

A pharmacokinetic model for estimating exposure of Americans to dioxin-like compounds in the past, present, and future

Empirical evidence suggests that exposure of Americans to dioxin-like compounds was low during the early decades of the 20th century, then increased during the 1940s and 1950s, reaching a peak in the 1960s and 1970s, and progressively decreased to lower levels in the 1980s and 1990s. Such evidence includes dioxin analysis of carbon-dated sediment cores of lakes and rivers, preserved meat samples from different decades of the 20th century, and limited body burden measurements of dioxin-like compounds. Pinsky and Lorber (1998) summarized studies measuring 2,3,7,8-TCDD in blood and adipose tissue, and found a range of 10-20 pg/g (ppt) lipid during the 1970s, and 2-10 ppt lipid during the 1980s. This study reviews body burdens of dioxin toxic equivalents, TEQs, to find a range from approximately 50 to 80 ppt lipid during the 1970s, 30-50 ppt lipid during the 1980s, and 10-20 ppt lipid during the 1990s (TEQs comprised of the 17 dioxin and furan congeners only). Pinsky and Lorber (1998) investigated historical exposure trends for 2,3,7,8-TCDD by using a single-compartment, first-order pharmacokinetic model. The current study extends this prior effort by modeling dioxin TEQs instead of the single compound, 2,3,7,8-TCDD. TEQs are modeled as though they were a single compound, in contrast to an approach where the individual dioxin and furan congeners are modeled separately. It was found that body burdens of TEQs during the 1970s, 1980s and 1990s could be modeled by assuming a historical dose which began the century at low levels of approximately 0.5 pg TEQ/kg/day, rose during the middle decades of the 20th century to over 6 pg TEQ/kg/day, and declined to current levels of approximately 0.5 pg TEQ/kg/day. Trends in individual and population body burdens of TEQs are also investigated using this PK modeling framework. A key uncertainty of this effort - assuming that TEQs behave as though they were a single compound - is discussed and analyzed.

Parents worried about breast milk contamination. What is best for baby?

Breast milk contamination may concern parents who are worried about their infant's exposure to environmental or occupational chemicals. This article examines the risks posed by chemicals in breast milk compared to the risks of formula feeding. In addition, this article provides guidance to health care professionals about how to evaluate maternal exposures that may influence breast milk quality. A guide to assessing potential exposures at home and in the workplace is provided.

Indirect exposure assessment at the United States Environmental Protection Agency

In the early 1980s, exposures and subsequent health impact assessments from contaminants emitted into the air from stationary sources focused on the inhalation pathway. This 'direct' pathway of exposure was thought to be the most critical pathway, as it is for many contaminants. However, by the latter 1980s, the focus at the Environmental Protection Agency (EPA) shifted to contaminants that would persist in the environment and could bioaccumulate up the food chain. Consumption of impacted food products, and other 'indirect' pathways of exposure, such as soil-related exposures, were shown to result in exposures that exceeded inhalation exposures by two to up to four orders of magnitude. A historical background of indirect exposure assessment at EPA is provided in this paper, followed by an overview of modeling methodologies commonly used in indirect exposure assessments. These methodologies are demonstrated on a contaminant of primary focus for indirect exposure impact, dioxins. Two examples are provided. In the first, an air-to-beef model validation exercise is described. In the second, an indirect exposure assessment on a municipal solid waste incinerator in Ohio conducted by the EPA is summarized. This incinerator emitted very large amounts of dioxin, more than any single source known to EPA. Models were used to predict the movement of dioxins from the stack to a nearby hypothetical farm, where individuals in the farm family were exposed to dioxins from consumption of home-produced beef and milk. The predicted lifetime cancer risk of 2.8 x 10(-4) based on these food pathways was used by EPA's Region 5 to initiate regulatory activity on this incinerator.