Breast-milk monitoring to measure Michigan's contamination with polybrominated biphenyls

Brominated flame retardants in breast milk from the United States: First detection of bromophenols in U.S. breast milk

Brominated flame retardants (BFRs) are a class of compounds with many persistent, toxic, and bioaccumulative members. BFRs have been widely detected in breast milk, posing health risks for breastfeeding infants. Ten years after the phaseout of polybrominated diphenyl ethers (PBDEs) in the United States, we analyzed breast milk from 50 U.S. mothers for a suite of BFRs to assess current exposures to BFRs and the impact of changing use patterns on levels of PBDEs and current-use compounds in breast milk. Compounds analyzed included 37 PBDEs, 18 bromophenols, and 11 other BFRs. A total of 25 BFRs were detected, including 9 PBDEs, 8 bromophenols, and 8 other BFRs. PBDEs were found in every sample but at concentrations considerably lower than in previous North American samples, with a median ∑PBDE concentration (sum of 9 detected PBDEs) of 15.0 ng/g lipid (range 1.46-1170 ng/g lipid). Analysis of time trends in PBDE concentrations in North American breast milk indicated a significant decline since 2002, with a halving time for ∑PBDE concentrations of 12.2 years; comparison with previous samples from the northwest U.S region showed a 70% decline in median levels. Bromophenols were detected in 88% of samples with a median ∑12bromophenol concentration (sum of 12 detected bromophenols) of 0.996 ng/g lipid and reaching up to 71.1 ng/g lipid. Other BFRs were infrequently detected but concentrations reached up to 278 ng/g lipid. These results represent the first measurement of bromophenols and other replacement flame retardants in breast milk from U.S. mothers. In addition, these results provide data on current PBDE contamination in human milk, as PBDEs were last measured in U.S. breast milk ten years ago. The presence of phased-out PBDEs, bromophenols, and other current-use flame retardants in breast milk reflects ongoing prenatal exposure and increased risk for adverse impacts on infant development.

Elimination of PBB-153; findings from a cohort of Michigan adults

BACKGROUND

An industrial accident led to the widespread contamination of polybrominated biphenyl (PBB), a flame retardant, into the food system in Michigan in the 1970's. PBB continues to be detected in Michiganders' blood some forty years later. It is necessary to understand the elimination rate and half-life of PBB because it may provide clues on how to hasten the elimination of it from the human body.

METHODS

Serum samples were taken from young adult and adult participants of the Michigan PBB registry from 1974 to 2019. A single compartment model was assumed for the elimination rate for PBB-153 in young adults and adults (≥16 years). Generalized linear mixed models were used to estimate the average elimination rate of PBB-153 and allowed for a random intercept and slope for the time between measurements. Models were adjusted for age at exposure, body mass index (BMI) at initial measurement, and smoking. Models were also stratified by demographic characteristics.

RESULTS

In total, 1974 participants contributed 4768 samples over a forty-year span. The median initial PBB-153 level was 1.542 parts per billion (ppb) (Range: 0.001-1442.48 ppb). The adjusted median participant-specific half-life for PBB-153 was 12.23 years. The half-life of PBB-153 was lengthened by higher initial PBB level (∼1.5 years), younger age at exposure (∼5.4 years), higher BMI (∼1.0 years), and increased gravidity (∼7.3 years). Additionally, the half-life of PBB-153 was shortened by smoking status (∼-2.8 years) and breastfeeding (∼-3.5 years).

CONCLUSIONS

Consistent with previous studies, PBB-153 has been demonstrated to have a long half-life in the human body and may be modified by some demographic characteristics. These updated estimates of half-life will further support evaluation of health effects associated with PBB exposure. Investigations into mechanisms to accelerate elimination and reduce body burdens of PBB-153, especially those related to body weight, are needed.

Sex-specific DNA methylation differences in people exposed to polybrominated biphenyl

Aim: Michigan residents were exposed to polybrominated biphenyls (PBBs) when it was accidentally added to the food supply. Highly exposed individuals report sex-specific health problems, but the underlying biological mechanism behind these different health risks is not known. Materials and methods: DNA methylation in blood from 381 women and 277 men with PBB exposure was analyzed with the MethylationEPIC BeadChip. Results: 675 CpGs were associated with PBBs levels in males, while only 17 CpGs were associated in females (false discovery rate <0.05). No CpGs were associated in both sexes. These CpGs were enriched in different functional regions and transcription factor binding sites in each sex. Conclusion: Exposure to PBBs may have sex-specific effects on the epigenome that may underlie sex-specific adverse health outcomes.

Organic contaminants in human breast milk identified by non-targeted analysis

Understanding the health implications of human exposure to mixtures of chemical contaminants is aided by analytical methods that can screen for a broad range of both expected and unexpected compounds. We performed a proof-of-concept analysis combining human breast milk, a biomonitoring matrix for determining contaminant exposure to mothers and infants, with a non-targeted method based on comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC/TOF-MS). A total of 172 presumably anthropogenic halogenated compounds and non-halogenated cyclic and aromatic compounds were tentatively identified in breast milk from San Diego, California through mass spectral database searches. Forty of the compounds were prioritized for confirmation based on halogenation or 100% frequency of detection, and the identities of 30 were verified using authentic standards. Thirty-four (85%) of the prioritized contaminants are not typically monitored in breast milk surveys, and 31 (77%) are regulated in at least one market worldwide, indicating breast milk may be a useful biomonitoring matrix for non-targeted analysis and the assessment of human exposure to future emerging or undiscovered contaminants.

The molecular mechanism of the antagonistic activity of hydroxylated polybrominated biphenyl (OH-BB80) toward thyroid receptor β

Polybrominated biphenyls (PBBs) were widely used as additive brominated flame retardants. Their hydroxylated products (OH-PBBs) have been detected frequently in various marine mammals, causing an increased health risk. Till now, there lacks information on the potential disruption of OH-PBBs toward thyroid hormone receptor (TR) and the molecular characteristics of their interactions remain largely unknown. We herein in vitro and in silico evaluated the disrupting effect of 3,3',5,5'-tetrabromobiphenyl (BB80) and its metabolite 2,2'-dihydroxy- 3,3',5,5'-tetrabromobiphenyl (OH-BB80) toward human TR. The recombinant human TRβ two-hybrid yeast assay reveals the moderate antagonistic activity of OH-BB80 with IC₂₀ at 2 μmol/L, while BB80 shows no agonistic or antagonistic activity. OH-BB80 binds at the binding cavity of TRβ ligand binding domain (LBD) and forms one hydrogen bond with Phe272. Electrostatic interactions and hydrophobic interactions contribute much to their interactions. The binding of OH-BB80 quenches the intrinsic fluorescence of TRβ LBD at static quenching mode. Our study extends knowledge on the endocrine disrupting effect of OH-PBBs and suggests the full consideration of the biotransformation for further health risk assessment of PBBs and related structurally similar emerging contaminants.

Exposure to polybrominated biphenyl (PBB) associates with genome-wide DNA methylation differences in peripheral blood

In 1973, Michigan residents were exposed to polybrominated biphenyl (PBB) when it was accidentally added to farm animal feed. Highly exposed individuals and their children have experienced endocrine-related health problems, though the underlying mechanism behind these remains unknown. We investigated whether PBB exposure is associated with variation in DNA methylation in peripheral blood samples from 658 participants of the Michigan PBB registry using the MethylationEPIC BeadChip, as well as investigated what the potential function of the affected regions are and whether these epigenetic marks are known to associate with endocrine system pathways. After multiple test correction (FDR <0.05), 1890 CpG sites associated with total PBB levels. These CpGs were not enriched in any particular biological pathway, but were enriched in enhancer and insulator regions, and depleted in regions near the transcription start site or in CpG islands (p < 0.05). They were also more likely to be in ARNT and ESR2 transcription factor binding sites (p = 3.27e-23 and p = 1.62e-6, respectively), and there was significant overlap between CpGs associated with PBB and CpGs associated with estrogen (p < 2.2e-16). PBB-associated CpGs were also enriched for CpGs known to be associated with gene expression in blood (eQTMs) (p < 0.05). These eQTMs were enriched for pathways related to immune function and endocrine-related autoimmune disease (FDR <0.05). These results indicate that exposure to PBB is associated with differences in epigenetic marks that suggest that it is acting similarly to estrogen and is associated with dysregulated immune system pathways.

Serum Polybrominated Biphenyls (PBBs) and Polychlorinated Biphenyls (PCBs) and Thyroid Function among Michigan Adults Several Decades after the 1973-1974 PBB Contamination of Livestock Feed

BACKGROUND

In 1973-1974, Michigan residents were exposed to polybrominated biphenyls (PBBs) through an accidental contamination of the food supply. Residents were enrolled in a registry assembled after the incident, and they and their children participated in follow-up studies to assess subsequent health outcomes.

OBJECTIVES

We evaluated associations between serum PBBs and polychlorinated biphenyls (PCBs) and markers of thyroid function among Michigan adults.

METHODS

Serum concentrations of four PBB and four PCB congeners were measured at least once in 753 adults, including 79 women who participated in a 2004-2006 study and 683 women and men with follow-up during 2012-2015. Participants completed questionnaires on health conditions (including physician-diagnosed thyroid disease), behaviors, and demographics. Thyroid hormones were measured in a subset without thyroid disease (n=551). In multivariable linear regression models, PBB and PCB congener concentrations, on both the volume (nanogram/milliliter) and lipid (nanogram/gram lipid) basis, were assessed in relation to thyroid hormones. Logistic regression models were used to estimate associations between serum PBBs and PCBs and thyroid disease.

RESULTS

Thyroid disease was common (18% overall; 25% among women). Among women, all odds ratios (ORs) for PBB-153 and thyroid disease were positive for quintiles above the reference level, but estimates were imprecise and were without a monotonic increase. For an interquartile range (IQR) increase in PBB-153 (0.43 ng/mL), the OR (any thyroid disease)=1.12; (95% CI: 0.83, 1.52) (n=105 cases); for hypothyroidism, OR=1.35 (95% CI: 0.86, 2.13) (n=49 cases). There were 21 cases of thyroid disease in men [OR=0.69 (95% CI: 0.33); 1.44 for an IQR increase (0.75 ng/mL) in serum PBB-153]. PCB congeners were statistically significantly associated with greater total and free thyroxine and total triiodothyronine among women and with total and free triiodothyronine among men in lipid-standardized models.

CONCLUSIONS

We found some evidence to support associations of PBBs and PCBs with thyroid disease and thyroid hormone levels. https://doi.org/10.1289/EHP1302.

Human Breast Milk Contamination in the United States and Canada by Chlorinated Hydrocarbon Insecticides and Industrial Pollutants: Current Status

Widespread contamination of human breast milk with chlorinated hydrocarbon insecticides has been repeatedly documented in population surveys in the United States and Canada over the past two decades. Unfortunately, it was not until the most recently published assessments that a strong effort has been made to apply proper biostatistical sampling methodologies to such surveys. This deficiency, along with frequent omission of information on variables known to affect the levels of such contaminants in breast milk, makes precise historical comparisons difficult. Given these uncertainties, it appears that organochlorine insecticide residues in human breast milk have not noticeably changed over the past two decades in the United States despite the regulatory restriction placed on several of these substances, such as DDT, since 1970. The surveys have revealed that total DDT levels continue to approach and exceed the Acceptable Daily Intake (ADI) level recommended by WHO. Perhaps of greatest concern is the ubiquitous contamination by polychlorinated biphenyls (PCBs) of breast milk, with levels of the upper 30% of the population being within a factor of 10 of those levels producing adverse health effects in humans and monkeys. The carcinogenic risk assessment for consumption of PCB-contaminated breast milk is also discussed.

Effects of Purified Polybrominated Biphenyl Congeners on the Thyroid and Pituitary Glands in Rats

Young male rats were fed diets containing 0, 1, 10, or 100 ppm of Firemaster (FM) BP-6 for 30 days and thyroidal and hypophyseal effects were compared with those caused by feeding identical amounts of either 2, 2', 4, 4', 5, 5'-hexabromobiphenyl (HBB) or 2, 3', 4, 4',5,5'-HBB, two of the congeners in FM BP-6. In addition, rats were given dietary levels of 0,1, or 10 ppm of 3,3', 4,4', 5, 5-HBB, a congener not in FM BP-6, but used because it is a 3-methylcholanthrene (MC)-type inducer of hepatic drug metabolizing enzymes. Thyroid weight was increased by 100 ppm FM BP-6 and by 1 and 10 ppm 3, 3', 4, 4', 5, 5'-HBB. Serum thyroxine concentrations were decreased by the highest dose of the same two chemicals. Extensive hyperplasia and hypertrophy of follicular cells and a lack of colloid were prominent lesions at the highest doses of each of the chemicals. The most severe ultrastructural alterations were seen at 10 ppm 3, 3', 4, 4', 5, 5'-HBB and 100 ppm FM BP-6. A dramatic increase in lysosomal bodies was seen at these doses. In addition, cytoplasmic colloid droplets were increased and microvilli were decreased. The Golgi apparatus was hypertrophied and the cisternae of the reticulum were dilated. Lesions were less severe with 2, 2', 4, 4', 5, 5-HBB and 2, 3', 4, 4', 5, 5-HBB, although more lysosomal bodies were seen with 2, 3', 4, 4', 5, 5-HBB than with 2, 2', 4, 4', 5, 5-HBB. Chromophobe cells in the pars anterior of the pituitary gland were swollen and vacuolated in rats fed diets containing 10 ppm 3, 3', 4, 4', 5, 5'-HBB. The results indicate that histologic and ultrastructural changes can occur with any of the chemicals used but the major functional and ultrastructural thyroidal changes seen in rats given FM BP-6 are most likely caused by congeners other than 2, 2', 4, 4', 5, 5-HBB or 2, 3', 4, 4, 5, 5-HBB.

A study on the levels of a polybrominated biphenyl in Chinese human milk samples collected in 2007 and 2011

The levels of a 2,2',4,4',5,5'-hexabromobiphenyl (BB-153) were measured in human milk samples collected in 2007 and 2011 from residents in China by high-resolution gas chromatography-high-resolution mass chromatography (HRGC-HRMS) with isotope dilution. The median concentrations of BB-153 from the samples collected in 2007 and 2011 were 8.3 and 7.2 pg/g lipid weight, respectively. The levels of BB-153 in the human milk collected from rural areas were not significantly different to those collected from the urban areas in China. Meanwhile, significant positive correlations were found between the levels of BB-153 in human milk and the consumption of animal-origin foods. In the present study, the mean levels of BB-153 in human milk from Chinese mothers were found to be lower than those from European and American mothers.

Suppression of thyroid hormone receptor-mediated transcription and disruption of thyroid hormone-induced cerebellar morphogenesis by the polybrominated biphenyl mixture, BP-6

Polybrominated biphenyls (PBBs) are polyhalogenated, bioaccumulative flame retardant chemicals, which have been used in a variety of consumer and household products. They were accidentally introduced into the food chain in Michigan in 1973 and have remained a source of health concern. Studies have shown that exposure to PBB may cause adverse neurotoxic effects. We therefore examined the effects of BP-6, a PBB mixture, on thyroid hormone (TH) receptor (TR)-mediated transcription, on TH-induced Purkinje cell dendritogenesis, and on TH-induced cerebellar granule cell neurite extension. Our study shows that BP-6 suppressed TR-mediated transcription in CV-1 cells. Mammalian two-hybrid studies revealed that BP-6 did not inhibit coactivator binding to TR nor did it recruit corepressors to TR. Further examination using the liquid chemiluminescent DNA pull down assay revealed partial dissociation of TR from TH response element (TRE). In primary rat cerebellar culture, BP-6 significantly suppressed TH-induced dendrite arborization of Purkinje cells, and in reaggregate rat granule cell culture, impaired TH-induced neurite extension of granule cells. Taken together, our results indicate that BP-6 may disrupt TH homeostasis and consequently impair normal neuronal development.

Assessing inter-generational transfer of a brominated flame retardant

Studies have shown that the lipophilic nature of polybrominated biphenyl (PBB) causes it to preferentially accumulate in breast milk posing a potential hazard for suckling infants. The purpose of this study was to examine the inter-generational transfer of PBB from mother to child and whether this association was modified by maternal breast-feeding patterns. One hundred and forty-five mother-child pairs that were participants of the Michigan Long-Term PBB Study were included in this analysis. Mothers were exposed to PBB via contaminated food between 1973 and 1974 and children were exposed in utero and for some, through breast-feeding. Seventy-three percent of children had a non-detectable serum PBB concentration (limit of detection (LOD) = 1 microg L(-1)). Mothers' serum PBB concentration at enrollment ranged from <LOD to 933 microg L(-1). The following variables were associated with the child having a detectable serum PBB concentration: maternal serum PBB > or =8 microg L(-1), breast-feeding > or =5.5 months, maternal age at child's birth > or =28 years, and being born during the PBB exposure period. Among mothers with a detectable serum PBB concentration, those who breast-fed > or =5.5 months were 6 times more likely to have a child with a detectable serum PBB concentration, compared to a non-breast-fed child (95% C.I., 2.0-19.6).

Reporting individual test results of environmental chemicals in breastmilk: potential for premature weaning

OBJECTIVE

Environmental chemicals are readily measured in human milk. Although it is imperative to conduct studies on frequency of detection and effects of exposures to environmental chemicals in human milk, the potential impact of reporting individual test results to lactating women is poorly understood. The purpose of this study was to determine if mothers want to know if chemicals are in their breastmilk and if knowing the results would alter their breastfeeding practices.

METHODS

We surveyed 381 mothers who were participating in a longitudinal birth cohort about whether they wanted to receive individual test results for environmental chemicals in their milk and whether they would alter their breastfeeding patterns if they were told that their milk contained "low" or "high" levels of phthalates.

RESULTS

Among the women who breastfed, 68% said that they wanted to know if there were chemicals in their breastmilk. Of breastfeeding women, 78% and 93% of mothers reported that they would either discontinue breastfeeding sooner than intended or pump and discard their milk if they were told they had "low" or "high" levels of phthalates in their milk, respectively. African American women were significantly more likely than Caucasian women to report that they would immediately wean if told of phthalates in their milk.

CONCLUSIONS

Concern about environmental chemicals in breastmilk may lead to early termination of breastfeeding. Chemical manufacturers and researchers should recognize the potential implications of isolating and reporting environmental chemicals in breastmilk.

Recent global trends and physiologic origins of dioxins and furans in human milk

Restrictions on releases of polychlorinated dibenzo-dioxins and polychlorinated dibenzofurans (PCDDs/Fs) to the environment from industrial practices have resulted in an attendant decrease in levels of these compounds in the environment. Continued environmental monitoring and biomonitoring of PCDDs/Fs ensure that exposures do not increase unexpectedly or unnoticed. Perhaps the most highly exposed part of the population, however, is the breastfed infant and a periodic assessment of levels of dioxins and furans in human milk provides exposure information for infants. A previous international review of levels of PCDDs/Fs in human milk based on data from the 1970's to the mid-1990's showed a decline in many countries for which data were available. In this paper, recent (1998-2005) global data on PCDDs/Fs in human milk are described. A comparison of these recent data to pre-1998 data suggests a continuing decline in global levels of PCDDs/Fs in human milk. In addition, this paper explores research on physiological origins of these compounds in human milk (e.g., adipose tissue mobilization, recent dietary exposures). The question of whether the presence of PCDDs/Fs in milk is from the lifetime accumulation of PCDDs/Fs in adipose tissue or current diet (or, as is more likely, a complex combination of both) remains unanswered. Whether diet during lactation has a greater influence on milk levels PCDDs/Fs levels than previously suspected, and whether infant exposures to PCDDs/Fs via breastfeeding could be reduced by changes in diet during lactation, are important--and currently unexplored--lines of inquiry.

Depuration of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) in breast milk from California first-time mothers (primiparae)

BACKGROUND

Little is known about the rates of loss (depuration) of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) from mothers during lactation. Depuration rates affect infant exposure to chemicals during breast-feeding, and fetal and lactational transfers during subsequent pregnancies.

OBJECTIVE

Our objective in this study was to estimate depuration rates of PBDEs and PCBs using serial samples of breast milk.

METHOD

Nine first-time mothers (primiparae) each collected samples at 4, 6, 8, 12, 16, 20, and 24 weeks after birth. Nine additional primiparae each collected two samples at varying time intervals (18 to > 85 weeks after birth). Analytical precision was assessed to evaluate the accuracy of measured monthly percentage declines in PBDEs and PCBs.

RESULTS

The four major PBDE congeners decreased 2 or 3% +/- 1% per month over the 6-month period. These decreases were consistent over a 50-fold range (21-1,330 ng/g lipid weight) of initial PBDE concentrations in breast milk. The change in PCB-153 ranged from + 0.3% to -0.6% per month, with heterogeneous slopes and greater intraindividual variability. PBDE and PCB concentrations declined 1% per month over longer periods (up to 136 weeks).

CONCLUSIONS

Our data indicate that PBDEs and PCBs are not substantially (4-18%) reduced in primiparae after 6 months of breast-feeding. Consequently, the fetal and lactational exposures for a second child may not be markedly lower than those for the first. Participants were volunteers from a larger study population (n = 82), and were typical in their PBDE/PCB levels and in many demographic and lifestyle factors. These similarities suggest that our results may have broader applicability.

Human milk research for answering questions about human health

Concerns regarding human milk in our society are diverse, ranging from the presence of environmental chemicals to the health of breastfed infants and the economic value of breastfeeding to society. The panel convened for the Technical Workshop on Human Milk Surveillance and Biomonitoring for Environmental Chemicals in the United States, held at the Hershey Medical Center, Pennsylvania State College of Medicine, on 24--26 September 2004, considered how human milk research may contribute to environmental health initiatives to benefit society. The panel concluded that infant, maternal, and community health can benefit from studies using human milk biomonitoring. Unlike other biological specimens, human milk provides information regarding exposure of the mother and breastfed infant to environmental chemicals. Some of the health topics relevant to this field of research include disorders of growth and development in infants, cancer origins in women, and characterization of the trend of exposure to environmental chemicals in the community. The research focus will determine the design of the study and the need for the collection of alternative biological specimens and the long-term storage of these specimens. In order to strengthen the ability to interpret study results, it is important to identify reference ranges for the chemicals measured and to control for populations with high environmental chemical exposure, because the amount of data on environmental chemical levels in human milk that is available for comparison is extremely limited. In addition, it will be necessary to validate models used to assess infant exposure from breastfeeding because of the variable nature of current models. Information on differences between individual and population risk estimates for toxicity needs to be effectively communicated to the participant. Human milk research designed to answer questions regarding health will require additional resources to meet these objectives.

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.

American Academy of Pediatrics Committee on Drugs. Transfer of drugs and other chemicals into human milk

The American Academy of Pediatrics places emphasis on increasing breastfeeding in the United States. A common reason for the cessation of breastfeeding is the use of medication by the nursing mother and advice by her physician to stop nursing. Such advice may not be warranted. This statement is intended to supply the pediatrician, obstetrician, and family physician with data, if known, concerning the excretion of drugs into human milk. Most drugs likely to be prescribed to the nursing mother should have no effect on milk supply or on infant well-being. This information is important not only to protect nursing infants from untoward effects of maternal medication but also to allow effective pharmacologic treatment of breastfeeding mothers. Nicotine, psychotropic drugs, and silicone implants are 3 important topics reviewed in this statement.

Relative lipid content as the sole mechanistic determinant of the adipose tissue:blood partition coefficients of highly lipophilic organic chemicals

The adipose tissue:blood partition coefficient (PCat:b) refers to the ratio of chemical concentration or solubility in adipose tissue and blood. The solubility of a chemical in adipose tissue or whole blood is equal to the sum total of its solubility in lipid and water fractions of these matrices. For highly lipophilic organic chemicals (HLOCs, i.e., chemicals with log n-octanol:water partition coefficients (PCo:w) greater than four), their solubility in the water fractions of both tissue and blood is negligible, and therefore their solubility in lipid fractions of tissue and blood alone determines PCat:b. Since the numerical value representing chemical solubility in lipids is likely to be the same for both blood lipids and adipose tissue lipids, the PCat:b values should be hypothetically, equal to the ratio of lipid content of adipose tissue and blood. The objective of the present study was therefore to verify whether the PCat:bs of HLOCs (volatile organics, dioxins, PCBs, PBBs, DDT) are equal to the ratio of adipose tissue and blood lipid levels. The data on lipid content of rat and human blood and adipose tissues were obtained from the literature. The calculated tissue:blood lipid ratios were comparable to the human and rat PCat:b of volatile organic chemicals, dioxins, PCBs, PBBs and/or DDT obtained from the literature. These results then suggest that, regardless of the identity and PCo:w of HLOCs, their PCat:b is equal to the ratio of lipid in adipose tissues and blood.

The human health effects of DDT (dichlorodiphenyltrichloroethane) and PCBS (polychlorinated biphenyls) and an overview of organochlorines in public health

Organochlorines are a diverse group of persistent synthetic compounds, some of which are detectable in nearly everyone. Many organochlorines are endocrine disruptors or carcinogens in experimental assays. p,p'-DDE (dichlorodiphenyl-dichloroethene) and PCBs (polychlorinated biphenyls) comprise the bulk of organochlorine residues in human tissues. We reviewed relevant human data cited in the 1991-1995 Medline database and elsewhere. High-level exposure to selected organochlorines appears to cause abnormalities of liver function, skin (chloracne), and the nervous system. Of more general interest, however, is evidence suggesting insidious effects of background exposure. Of particular concern is the finding of neonatal hypotonia or hyporeflexia in relation to PCB exposure. The epidemiologic data reviewed, considered in isolation, provide no convincing evidence that organochlorines cause a large excess number of cancers. A recent risk assessment that considered animal data, however, gives a cancer risk estimate for background exposure to dioxin and dioxin-like compounds (e.g. some PCBs) with an upper bound in the range of 10(-4) per year.

Biochemical and biological markers: implications for epidemiologic studies

Given that a major task for environmental epidemiology is to provide clear evidence of immediate and long-term health risks so that appropriate preventive measures can be taken, biochemical and biological markers of potentially hazardous environmental exposures are of great interest and possibly of great value. Such markers fall into two discrete classes: (1) those quantitatively related to the exposure itself, reflecting the magnitude of such exposures or the body burden of the pollutants, and (2) those markers that reflect the biological response to such exposures. In this paper we discuss the use of biochemical and biological markers in epidemiologic studies. Methods are presented for the use of markers to decrease misclassification errors in exposure studies. Relationships are derived that give minimum required values for laboratory sensitivity and specificity. Markers are also discussed in terms of some of the inherent problems in their use (e.g., ethical and legal considerations) and the likelihood of acceptance by participants in epidemiologic studies, researchers, regulators, and health professionals.

Short-term oral administration of polybrominated biphenyls enhances the development of hepatic enzyme-altered foci in initiated rats

FireMaster BP-6 (FM), a commercial mixture of polybrominated biphenyls (PBB), has been shown to act as a tumor promoter in hepatocarcinogenesis assays in rats. Most hepatic tumor promoters must be administered for many weeks or months. Because FM is highly persistent in animal tissues, it was hypothesized that very short-term administration of FM would result in tumor promotion. Female Sprague-Dawley rats weighing 185-215 g were initiated by a two-thirds partial hepatectomy followed by 10 mg diethylnitrosamine/kg body weight (BW) 24 h later. Thirty days later, rats were gavaged with FM in corn oil, at total doses of 0, 13, or 130 mg FM/kg BW. Half the dose was given on d 30, and the remaining half was given 24 h later. At 120 d after gavage the rats were killed and necropsied. Five liver sections from each animal were histochemically stained for gamma-glutamyl transpeptidase-positive enzyme-altered foci (EAF). EAF were significantly increased over control values in initiated rats given 130 mg FM/kg. In animals given 13 mg FM/kg, EAF were increased to a lesser extent but not significantly above controls. Enhancement of these EAF in initiated rats reflects tumor-promoting activity. In this study, 24-h administration of FM in initiated rats was sufficient to enhance hepatic EAF measured 120 d later in an rats was sufficient to enhance hepatic EAF measured 120 d later in an initiation-promotion protocol, and a dose of 13 mg FM/kg was apparently close to a possible no-effect threshold level for enhancement of EAF.

Effect of polybrominated biphenyls on the growth and maturation of human peripheral blood lymphocytes

Polybrominated biphenyls (PBB) have been shown to affect the immune system of exposed Michigan farm workers and their families. The purpose of this study was to evaluate the effects of PBB on the function and on the synthesis of immunoglobulins by peripheral blood lymphocytes. Concentrations of PBB as low as 0.001 microgram/10(5) cells decreased lymphocyte response to pokeweed mitogen; higher concentrations of PBB stimulated the in vitro synthesis and release of immunoglobulins. PBB had no effect on the quantity of E-rosette-forming cells, the total T or B cells, or the ratio of helper to suppressor T-cell subpopulations. Enhanced release of IgG was identified in lymphocyte cultures obtained from blood specimens of PBB-exposed Michigan farmers. The data from this study suggest that PBB exerted an adverse effect on cell function, but produced a nonspecific activation of B lymphocytes.

[The liver and environmental poisons]

For almost a century now numerous examples of acute and subacute hepatic injury from exposure to toxic agents in the occupational or non-occupational environment have been extensively studied and are well documented, but such events are comparatively rare. In contrast, epidemiological data associating exposure to environmental chemicals with chronic liver disease or primary hepatic malignancies in the human is scarce as compared with the vast body of literature concerning chronic pulmonary disease as a consequence of exposure at the workplace. Large-scale industrial production of many newly synthesized organic chemicals began during the period 1930-1940 but it was not until the 1960s that the output increased exponentially. Consequently, the spectrum of environmental influences is gaining increasing complexity since simultaneous or sequential exposure to a variety of pollutants is becoming the rule rather than the exception. Possible interaction or synergism of environmental agents--even of those which in themselves or for their low dosage level may be considered "harmless" - and particularly latency periods of more than one decade further complicate preventive strategies. The liver, as the central site for the biotransformation of xenobiotics, deserves special attention when new chemicals which are to be introduced into the environment are being tested for their potential toxicity, especially since many hepatotoxic agents have been shown to undergo bioactivation in the liver. Currently available information on hepatic injury due to environmental agents is briefly reviewed and comprises solvents and degreasing agents, pesticides, polyhalogenated biphenyls, dioxins and dibenzofuranes, epoxy resin hardeners, vinyl chloride, naturally occurring hepatotoxins in plants and fungi, herbal medicines and traditional remedies and a side-light on the Reye syndrome and the Spanish "toxic oil syndrome".

Chloracne and chloracnegens

Chloracne, an acneform eruption resulting from poisoning by halogenated aromatic compounds, has been a considerable problem over the last 40 years. The condition is always a symptom of systemic poisoning and should be familiar to all practitioners, particularly dermatologists. It is difficult to treat and can last for long periods without known additional exposure to chloracnegens. Some chloracnegens are capable of causing a variety of systemic signs and symptoms and may be oncogenic. Although there are probably fewer than 4,000 persons with chloracne worldwide, those found with the disorder should be evaluated medically on a regular basis and followed, if possible, throughout their lives.

The PBB episode in Michigan: an overall appraisal

Polybrominated biphenyls (PBB) were used as a fire retardant. In common with other halogenated hydrocarbons, PBBs are lipophilic and resistant to chemical and metabolic degradation. Cattle on about 25 Michigan farms were exposed to as much as 250 g per head of PBB when it was accidentally mixed in cattle feed in 1973 to 1974. Livestock exposures several orders of magnitude lower occurred on several hundred other farms because of carryover and equipment contamination in feed mills. Approximately 85% of the Michigan population received some exposure to PBB because dairy product marketing involves mixing milk from many farms. A few cases of high human exposure, which may have been as great as 10 g, occurred when residents of the more highly exposed farms consumed their own products. Although numerous clinical signs and pathological changes were reported in exposed cattle, only anorexia, lacrimation, emaciation, hyperkeratosis, and kidney damage were confirmed in controlled studies. The acute toxicity of PBB in laboratory animals is low, but a variety of subacute effects have been reported. Induction of microsomal enzymes, enlargement and histopathological changes of the liver, fetotoxicity, and immunosuppression are among the more significant. Epidemiological studies of exposed humans have revealed no pattern of clinical signs or symptoms that were related to PBB exposure. A complete evaluation of the human consequences of exposure to PBB await the conclusion of long-term epidemiological studies.

Polybrominated biphenyls and fetal mortality in Michigan

The contamination of the Michigan food supply by polybrominated biphenyls (PBBs) in the mid-1970s appears to have had little or no impact on fetal mortality. Comparison of fetal death rates among residents of Lower Peninsula counties with a high percentage of quarantined farms and among residents of Upper Peninsula counties with no quarantined farms reveals no important differences in rates or trends after the contamination. Since counts of early spontaneous abortions are lacking, a complete assessment of the possible impact on reproductive outcome cannot be made.

Polychlorinated biphenyls (PCBs) and polybrominated biphenyls (PBBs): biochemistry, toxicology, and mechanism of action

Polychlorinated and polybrominated biphenyls are industrial chemical mixtures which have been implicated in numerous human poisonings in Taiwan and Japan (PCBs) and Michigan (PBBs). Moreover, these polyhalogenated biphenyls have been widely detected in the environment including the air, water, fish, wildlife, human adipose tissue, and blood and breast milk. A major problem associated with the analysis and toxicology of this group of chemicals is their chemical complexity (e.g., there are 209 possible PCB isomers and congeners) and the remarkable effects of structure on activity. This article will discuss the effects of structure on the biologic and toxic effects of individual PCB and PBB congeners as well as reconstituted mixtures. The results clearly show that like "dioxin" (or 2,3,7,8-TCDD), the PCBs and PBBs elicit their effects through a cytosolic receptor protein which preferentially binds with the toxins which are approximate isostereomers of 2,3,7,8-TCDD. The evidence for this mechanism of action will be discussed in detail.

Transplacental and milk transfer of polybrominated biphenyls to perinatal guinea pigs from treated dams

Timed-pregnant albino Hartley strain guinea pigs of approximately 65 days gestation or lactating animals within 6-12 h of parturition received a single oral dose of Firemaster FF-1 (50 mg/kg body wt). The pregnant animals and their fetuses were killed 2 days later at term while the lactating animals and their pups were killed at intervals of 2, 4, 7, 14, 28, 42, and 60 days. Tissues (liver, kidney, lung, perirenal fat) were removed for the analysis of the 2,4,5,2',4',5'-hexabromobiphenyl (HBB) isomer content by gas-liquid chromatography following extraction. Microsomes were prepared from samples of fresh liver for the analysis of hepatic mono-oxygenase (p-nitroanisole O-demethylase, aniline hydroxylase) and UDP-glucuronosyl-transferase activities. Transplacentally-acquired residues of the order of 45 micrograms HBB/g were found in both maternal and fetal adipose tissue and in fetal liver. HBB residues in maternal kidney, lung and liver were of the order of 4-7 micrograms/g while, in the fetuses and pups, levels in the kidney and lung were of the order of 1-2 micrograms/g. Levels of HBB in breast milk 2 days after treatment averaged 22.4 +/- 7.8 micrograms/g (mean +/- S.D.). A marked induction of hepatic microsomal mono-oxygenases was observed in guinea pig pups concomitant with elevated hepatic levels of HBB (9-19 micrograms/g) which decreased with time as the agent was redistributed into adipose tissue. By 7 days of age the pups had been weaned and by 14 days of age the enzymatic activities were comparable to those measured in control pups. HBB levels in the pup kidney, lung and adipose tissue reflected redistribution or sequestration in the body fat. The biological half-life of HBB in tissues of both dams and pups appeared to be approximately 22 days.

Contamination of the food chain by polychlorinated biphenyls from a broken transformer

In 1979, widespread distribution of chicken and egg food products and grease contaminated with polychlorinated biphenyl (PCBs) occurred across the United States and as far away as Canada and Japan. The contamination was traced to an accidental leakage of PCBs from a transformer stored in a hog slaughtering plant in Montana. Breast milk analyses showed the PCB absorption had occurred among egg consumers. The episode illustrates the need for heightened vigilance over the fate of PCBs still in use.

Environmental politics and science: the case of PBB contamination in Michigan

This article examines how politics and science interacted against a background of uncertainty to shape policy in the case of environmental contamination by polybrominated biphenyls (PBB) in Michigan. In 1973, between 500 and 1,000 pounds of the flame retardant PBB were accidentally shipped and used instead of the dairy feed additive magnesium oxide, resulting in the widespread contamination of animal feeds, animals, and human food products. The contamination was initially perceived as the private trouble of a single farmer. The problem next became a public issue as public and private institutions grappled with questions of illness, safety, and disposal. To gain influence over those institutions, dissatisfied individuals and groups then turned the PBB contamination into a political controversy. The final section of the present article analyzes how science and politics interacted in: the ways bureaucratic organizations defined the three problems of contamination; the role political controversy played in redefining problems and influencing policy; and the political roles of scientists in controversies over environmental contamination.

Lake Michigan fish consumption as a source of polychlorinated biphenyls in human cord serum, maternal serum, and milk

Reported consumption of Lake Michigan sport fish was examined in relation to the levels of polychlorinated biphenyls (PCBs) in biological samples provided by a sample of maternity patients. Fish consumption was correlated with PCB levels in maternal serum and milk but not in cord serum. PCB levels in serum increased with age, but were unrelated to social class, parity, or weight. Women who breast fed consumed as much fish as women who did not and their maternal and cord sera PCB levels were similar.

Partitioning of polybrominated biphenyls (PBBs) in serum, adipose tissue, breast milk, placenta, cord blood, biliary fluid, and feces

Polybrominated biphenyl (PBB) concentrations in specimens from adult males and females were used to determine the distribution of PBBs in body tissues and the partitioning ratio between types of tissues. Specimens of serum, adipose tissue, biliary fluid, and feces were tested by gas chromatography. In addition, parturient women provided breast milk, placenta, and cord blood for testing. There was a significant correlation between serum and adipose PBB levels. Pregnant and nonpregnant women and male chemical workers had similar serum to adipose tissue concentration ratios, which ranged from 1:140 to 1:260. Males from farms had a significantly different ratio of 1:325-329. Potential exposure to the fetus and newborn was demonstrated. Cord blood contained one-tenth of the concentration found in maternal serum which indicated partial placental passage. Human milk contained PBBs at 107 to 119 times the quantity found in maternal serum. Polybrominated biphenyls were detectable in bile and feces demonstrating transfer into the intestinal tract. The concentration of PBBs in feces represented a minor proportion of the total body burden indicating a slow rate of excretion.

Cardiac and hepatic effects of pre- and postnatal exposure to polybrominated biphenyls in rats

Body weight gain and hepatic concentrations of vitamin A were reduced in Sprague-Dawley rats by pre- and postnatal exposure to 100 ppm polybrominated biphenyls (PBBs). The ratio of liver weight to body weight, activity of hepatic delta-aminolevulinic acid (ALA) synthetase, and urinary excretion of uro- and coproporphyrins were increased by PBBs. Treatment with PBBs also increased the left atrial inotropic response to calcium. However, PBBs had no effect on development of the adrenergic neuronal transport system in heart, left atrial baselike peak tension, or inotropic response to ouabain. Thus PBBs retarded body weight gain and produced a variety of alterations in liver, but had little effect on cardiac contractile function.

Nonrespiratory metabolic function and morphology of lung following exposure to polybrominated biphenyls in rats

Exposure to polybrominated biphenyls (PBBs) resulted in increased activity of microsomal arylhydrocarbon hydroxylase and ethoxyresorufin-O-deethylase in rat lung. Clearance of 5-hydroxytryptamine (5-HT) and angiotensin 1 by perfused lungs was decreased by PBBs. However, PBBs had no effect on the activity of epoxide hydrolase, monoamine oxidase, or angiotensin-converting enzyme in lung. The only histopathologic change detected in lungs from PBB-treated rats was an increase in alveolar type II cell lamellar bodies. Selective accumulation of certain PBB congeners by lung was not observed in this investigation.