Evaluation of Prenatal Exposure to Bisphenol Analogues on Development and Long-Term Health of the Mammary Gland in Female Mice
Continued efforts to phase out bisphenol A (BPA) from consumer products have been met with the challenges of finding safer alternatives.
Objectives This study aimed to determine whether early-life exposure to BPA and its related analogues, bisphenol AF (BPAF) and bisphenol S (BPS), could affect female pubertal mammary gland development and long-term mammary health in mice.
Timed pregnant CD-1 mice were exposed to vehicle, BPA (0.5, 5, 50mg/kg), BPAF (0.05, 0.5, 5mg/kg), or BPS (0.05, 0.5, 5mg/kg) via oral gavage between gestation days 10–17. Mammary glands were collected from resulting female offspring at postnatal day (PND) 20, 28, 35, and 56, and at 3, 8, and 14 months for whole mount, histopathological evaluation, and quantitative real-time polymerase chain reaction (qPCR); serum steroid concentrations were also measured at these time points.
In the bisphenol-exposed mice, accelerated mammary gland development was evident during early puberty and persisted into adulthood. By late adulthood, mammary glands from bisphenol-exposed female offspring exhibited adverse morphology in comparison with controls; most prominent were undifferentiated duct ends, significantly more lobuloalveolar hyperplasia and perivascular inflammation, and various tumors, including adenocarcinomas. Effects were especially prominent in the BPAF 5mg/kg and BPS 0.5mg/kg groups. Serum steroid concentrations and mammary mRNA levels of Esr1, Pgr, Ar, and Gper1 were similar to controls.
These data demonstrate that prenatal exposure of mice to BPAF or BPS induced precocious development of the mammary gland, and that siblings were significantly more susceptible to spontaneous preneoplastic epithelial lesions and inflammation, with an incidence greater than that observed in vehicle- and BPA-exposed animals.
Our findings suggest that exposure to BPAF and BPS by consumers such as women of child-bearing age or infants and children should be restricted. The fetal mammary gland is a sensitive target organ for these chemicals. BPAF and BPS prenatally exposed female mice developed proliferative epithelial lesions by midlife, concomitant with a significant inflammatory response that may predispose them to tumor formation later in life. In fact, animals in the high-dose BPS group developed adenocarcinomas prior to one year of life and those diagnoses triggered a necropsy at 14 months of age in the remaining animals. Most neoplasia incidents in this study (7/8) occurred in the BPS-exposed animals. The extended presence of TEBs into adulthood (confirmed by histopathology), the significant prepubertal spikes in serum estradiol, and the altered immune responses (e.g., increased perivascular inflammation) may have been important modifiers of the persistent adverse effects observed later in life. To our knowledge, this study is the first report of BPAF- and BPS-induced adverse developmental effects in the mammary gland, and these findings warrant further studies to determine relevance of these findings for human breast cancer susceptibility. Featured image credit PNAS.
Science has shown that many thousands of people have been exposed to now mostly banned chemicals such as lead and PCBs at high enough levels to have had their brain development negatively affected. This report finds that there are other chemicals which are still in routine use in our homes where there is evidence of similar developmental neurotoxic (DNT) properties, and also identifies huge gaps in our knowledge of the impacts of other chemicals on brain development. It also points out the unpleasant reality that we are constantly exposed to a cocktail of chemicals, something which is still largely ignored by chemical safety laws.
In spite of the lessons of the past, regulators are continuing to only regulate after harm is caused, instead of acting to effectively protect the most precious of things; children’s developing brains.
In June 2007 CHEM Trust wrote the briefing Chemicals Compromising Our Children, which highlighted growing concerns about the impacts of chemicals on brain development in children. Almost 10 years later, CHEM Trust has revisited the issue with this report, which includes contributions from two of the most eminent scientists in this area, Professor Barbara Demeneix (Laboratory of Evolution of Endocrine Regulations, CNRS, Paris) and Professor Philippe Grandjean (Department of Environmental Medicine, University of Southern Denmark, Denmark & Department of Environmental Health, Harvard T.H. Chan School of Public Health, Boston, USA), who also peer reviewed the report.
Our brain and its development
Our brains are astoundingly complex, made up of over 85 billion neurons, which have grown, developed and interconnected during our lives. The brain is the organ that takes the longest to develop, with initial stages of cell division, creation of neurons and their migration taking place from the first hours after fertilisation and throughout the foetus’ time in the womb. However, brain development does not stop at birth – it’s not until our twenties that neurons are fully developed with their myelin coats.
Throughout this complex developmental process a range of signalling chemicals and other processes operate in order to control what happens. The thyroid hormone system is intimately involved in brain development and function, yet it is well established that this system can be disrupted – for example by a lack of iodine (essential to make thyroid hormone) or by certain chemicals. If developmental processes are disrupted, this most often creates permanent problems.
The complexity of brain development and function means that deficits can be very subtle – small reductions in IQ, disabilities that exist with a broad spectrum of seriousness such as autism, or in some cases conditions which do not have fully agreed diagnostic criteria.
Disruption of brain development by chemicals
We are all exposed to hundreds of man-made chemicals in our daily life, coming from everyday products including food, furniture, packaging and clothes. Many of these chemicals will have no negative effects on us, but it is now well established that some are able to disrupt normal development of the brain. Chemicals with long established DNT properties such as lead, PCBs and methylmercury, have been joined by others where DNT effects have been identified more recently, and which are being used in everyday products. There are also rising concerns about chemicals that are very similar to chemicals that have had their use restricted, but which we continue to use as there isn’t sufficient information about their toxic effects. We know even less about thousands of other chemicals in routine use, which have had no testing for DNT properties.
Chemical exposures are so ubiquitous that experts have recognized that babies are born “pre-polluted”. Scientific paediatric and gynaecology & obstetrics societies have consistently warned about chronic health implications from both acute and chronic exposure to chemicals such as pesticides and endocrine disruptors.
The report identifies evidence of DNT properties for the following chemicals:
Bisphenol A (BPA)
a chemical that was used to make baby bottles, is currently being phased out of till receipts (in the EU), but is still used in the making of food can linings and many polycarbonate plastics. There are also concerns about closely related chemicals that are not restricted, including Bisphenol S.
Brominated Flame Retardants (BFRs)
a group of chemicals added to furniture, electronics and building materials. The evidence for neurodevelopmental effects is strongest for the PBDE (polybrominated diphenyl ether) group of BFRs, which are already banned or nearly banned in the EU, though they are still in furniture in our homes, and in dust. However, other BFRs are now being found in dust and human blood serum, with concerns that these BFRs might have similar effects.
a group of chemicals used as plasticisers in PVC and in other products. Some chemicals in this group are now banned in the EU, but many others are still in use.
Per- and poly-fluorocarbons (PFCs)
used as non-stick coatings or breathable coatings, are a large group of chemicals, a few of which are in the process of being restricted by the EU. There is evidence that some PFCs can disrupt the action of the thyroid hormone. PFCs are very persistent in the environment, and many of them can accumulate in our bodies – they are routinely found in blood.
a contaminant of food, related to the use of certain fertilisers and hypochlorite bleach, and is known to disrupt the thyroid hormone system.
Are we protected?
The EU has the most sophisticated regulations in the world for controlling chemical use. However, there are a number of key flaws in this system:
There is often inadequate safety information about individual chemicals, including a lack of information about neurodevelopmental effects.
The processes to ban chemicals are too slow, and the restrictions created often have big loopholes as a result of industry lobbying.
Chemicals are addressed one at a time, so one chemical may have its use restricted, but closely related chemicals remain in use.
We are always exposed to multiple chemicals, but regulations almost always assume we are only exposed to one at a time, even though numerous scientists have shown that chemical effects can add together in our bodies.
It is clear that our children are not currently being protected from chemicals that can disrupt brain development. We have identified a range of policy measures that could improve the situation, including:
Acting faster to ban chemicals of concern, including addressing groups of similar substances, not just those where we have the most information.
Ensuring that any safety testing of chemicals includes evaluation of DNT effects.
Ensuring better identification and regulation of neurodevelopmental toxic chemicals.
Ensuring that all uses of chemicals are properly regulated; for example there is a lack of effective regulation of chemicals in food packaging including paper, card, inks, glues and coatings.
The UK and Ireland should remove the requirement for an open flame test for furniture. This test is not required in the rest of the EU, and leads to increased use of flame retardant chemicals.
Finally, it is important to note that EU regulations have already controlled a number of chemicals of concern, and that EU laws provide a tool to address these problems. We therefore think it is vital for the UK Government to work to stay aligned with EU chemicals laws, whatever the eventual outcome of the UK’s Brexit process.
Though full protection will only come from proper regulation of chemicals, the report also includes a chapter with tips for reducing your and your family’s exposures in daily life.
Sources and More Information
Download the full report “No Brainer The impact of chemicals on children’s brain development: a cause for concern and a need for action”, chemtrust, 2017.
IT’S A NO BRAINER! Action needed to stop children being exposed to chemicals that harm their brain development!, chemtrust, MARCH 7, 2017.
Common BPA alternative, BPS, crosses into placenta
Bisphenol S (BPS), found in baby bottles, personal care products and thermal receipts, is a replacement chemical for BPA and was introduced when concern was raised about possible health effects of that plastic compound.
As with BPA, there is evidence that BPS is an endocrine disruptor. Canadian and Chinese scientists have found the “first evidence” that BPS can cross the human placenta.
2017 Study Abstract
Human studies show associations between maternal bisphenol A (BPA) exposure and developmental effects in children, yet biomonitoring of BPA metabolites in maternal and fetal serum remains limited, and less is known for BPA alternatives. BPA-glucuronide, BPA-sulfate, and bisphenol S (BPS) were quantified in 61 pairs of maternal and cord sera from Chinese participants.
Bisphenol A Metabolites and Bisphenol S in Paired Maternal and Cord Serum, Environmental Science & Technology, DOI: 10.1021/acs.est.6b05718, January 22, 2017.
Total BPS was only detectable in four maternal (<0.03–0.07 ng/mL) and seven cord sera (<0.03–0.12 ng/mL), indicating low exposure but providing the first evidence that BPS crosses the human placenta. Total BPA metabolites in cord serum were significantly higher than in maternal serum (p < 0.05), suggesting that these may be formed in the fetus or cleared more slowly from the fetoplacental compartment. Unlike the pharmacokinetic results from controlled oral exposure studies in which BPA-glucuronide is the major BPA metabolite, here, BPA-sulfate was the dominant metabolite (GM: 0.06 and 0.08 ng/mL), significantly higher than BPA-glucuronide (GM: 0.02 and 0.04 ng/mL) (p < 0.01) in both maternal and cord sera. Moreover, the proportion of BPA-sulfate increased with total BPA.
These are the first human data for BPA metabolites in paired maternal and cord serum, and results suggest that the human fetus and pregnant mother have unique exposure to BPA metabolites. Direct analysis of BPA metabolites in serum provides complementary information for evaluating early life-stage exposure and risks of BPA.
Bisphenol S (BPS) alters maternal behavior and brain in mice exposed during pregnancy/lactation and their daughters
BPS, found in baby bottles, personal care products and thermal receipts, is a replacement chemical for BPA and was introduced when concern was raised about possible health effects of that plastic compound. As with BPA, there is evidence that BPS is an endocrine disruptor.
In the first study of its kind, environmental health scientist Laura Vandenberg and neuroscientist Mary Catanese at the University of Massachusetts Amherst examined the effects of the compound bisphenol S (BPS) on maternal behavior and related brain regions in mice. They found subtle but striking behavior changes in nesting mothers exposed during pregnancy and lactation and in their daughters exposed in utero.
Estrogenic endocrine disrupting chemicals (EDCs) have been shown to disrupt maternal behavior in rodents. We investigated the effects of an emerging xenoestrogen, bisphenol S (BPS), on maternal behavior and brain in CD-1 mice exposed during pregnancy and lactation (F0 generation) and in female offspring exposed during gestation and perinatal development (F1 generation).
BPS affects maternal behavior as well as maternally relevant neural correlates
We observed different effects in F0 and F1 dams for a number of components of maternal behavior including time on the nest, time spent on nest-building, latency to retrieve pups, and latency to retrieve the entire litter. We also characterized expression of estrogen receptor (ER) alpha (α) in the medial preoptic area (MPOA) and quantified tyrosine hydroxylase (TH) immunoreactive cells in the ventral tegmental area (VTA), two brain regions critical for maternal care. BPS-treated females in the F0 generation had a significant increase in ERα expression in the caudal subregion of the central MPOA (cMPOA) in a dose dependent manner. In contrast, there were no significant effects of BPS on the MPOA in F1 dams or the VTA in either generation.
Uncovering effects of environmental chemicals that might influence proper maternal care have broad social and public health implications
This work demonstrates that BPS affects maternal behavior and brain with outcomes depending on generation, dose and postpartum period. Many studies examining effects of EDCs view the mother as a means by which offspring can be exposed during critical periods of development. Here, we demonstrate that pregnancy and lactation are vulnerable periods for the mother. We also show that developmental BPS exposure alters maternal behavior later in adulthood. Both findings have potential public health implications.
BPS, BPF, BPB and chlorinated derivatives likely to have similar effects than BPA
Bisphenol A (BPA) is a chemical that is widespread in the environment. Researchers reviewed and critically discussed the sources and routes of human exposure to chlorinated derivatives (ClxBPA) and alternatives to BPA (BPF, BPS), as well as their metabolism, toxicity and concentrations in human tissues. The researchers suggest BPA alternatives and derivatives may have similar effects, and provide directions for future research.
The high reactivity of bisphenol A (BPA) with disinfectant chlorine is evident in the instantaneous formation of chlorinated BPA derivatives (ClxBPA) in various environmental media that show increased estrogen-activity when compared with that of BPA.
The documented health risks associated with BPA exposures have led to the gradual market entry of BPA structural analogs, such as bisphenol S (BPS), bisphenol F (BPF), bisphenol B (BPB), etc. A suite of exposure sources to ClxBPA and BPA analogs in the domestic environment is anticipated to drive the nature and range of halogenated BPA derivatives that can form when residual BPA comes in contact with disinfectant in tap water and/or consumer products.
The primary objective of this review was to survey all available studies reporting biomonitoring protocols of ClxBPA and structural BPA analogs (BPS, BPF, BPB, etc.) in human matrices. Focus was paid on describing the analytical methodologies practiced for the analysis of ClxBPA and BPA analogs using hyphenated chromatography and mass spectrometry techniques, because current methodologies for human matrices are complex. During the last decade, an increasing number of ecotoxicological, cell-culture and animal-based and human studies dealing with ClxBPA exposure sources and routes of exposure, metabolism and toxicity have been published. Up to date findings indicated the association of ClxBPA with metabolic conditions, such as obesity, lipid accumulation, and type 2 diabetes mellitus, particularly in in-vitro and in-vivo studies. We critically discuss the limitations, research needs and future opportunities linked with the inclusion of ClxBPA and BPA analogs into exposure assessment protocols of relevant epidemiological studies.
Low-dose exposure to bisphenol A and replacement bisphenol S induces precocious hypothalamic neurogenesis in embryonic zebrafish
Bisphenol A, known as BPA, is a chemical produced in massive quantities around the world for use in consumer products, including household plastics. In response to public concerns, many manufacturers have replaced bisphenol A with a chemical called bisphenol S (BPS), which is often labelled as “BPA-free” and presumed to be safer.
In a new study, researchers in Deborah Kurrasch’s lab at the University of Calgary have provided evidence that BPA and BPS cause alterations in brain development leading to hyperactivity in zebrafish.
“I was actually very surprised at our results. This was a very, very, very low dose, so I didn’t think using a dose this low could have any effect,” says Kurrasch, PhD, a researcher in the University of Calgary’s Cumming School of Medicine and corresponding author on the paper.
For the study, Kurrasch worked with University of Calgary researcher Hamid Habibi, PhD, and Cassandra Kinch, a PhD student, to expose zebrafish embryos to concentrations of the chemicals at levels found in the Bow and Oldman rivers of southern Alberta. By doing this, exposure to BPA and BPS changed the timing when neurons were formed in the brains of the zebrafish.
Prenatal period a particularly sensitive stage
“These findings are important because they support that the prenatal period is a particularly sensitive stage, and reveals previously unexplored avenues of research into how early exposure to chemicals may alter brain development,” says Kinch.
“In the second trimester, brain cells become the specialized neurons that make up our brain. What we show is that the zebrafish exposed to BPA or BPS were getting twice as many neurons born too soon and about half as many neurons born later, so that will lead to problems in how the neurons connect and form circuits,” says Kurrasch, a member of the Alberta Children’s Hospital Research Institute and the Department of Medical Genetics.
Change in behaviour detected
Researchers discovered the number of neurons generated in the developing zebrafish brains increased by 180 per cent compared with unexposed fish. They also learned that BPS increased the number of neurons by 240 per cent in similar experiments. The result was a change in behaviour, with the fish demonstrating greater hyperactivity later in life.
Another surprise finding was that zebrafish receptors targeted by BPA and BPS to mediate this early neuronal birth in zebrafish brains were androgen receptors. Assumptions based on numerous reports postulated that BPA and BPS modulate normal physiology by mimicking the endogenous sex steroid estrogen, and not testosterone.
“Finding the mechanism linking low doses of BPA to adverse brain development and hyperactivity is almost like finding a smoking gun,” says Habibi, a professor of environmental toxicology and comparative endocrinology in the Faculty of Science.
A caution for pregnant women
Although further research is needed to explore that link and the potential effect on human brains developing in the womb, Kurrasch says the findings add weight to other studies suggesting pregnant women should try to limit their exposure to items containing bisphenols. The evidence also supports removing all bisphenols and structurally similar chemicals from consumer products, she says.
Zebrafish are a widely accepted biomedical model for understanding embryonic brain development. About 80 per cent of the genes found in people have a counterpart in zebrafish — and possess very similar developmental processes as humans.
Sources and more information
Zebrafish study shows bisphenols affect embryonic brain development, University of Calgary, January 13, 2015.
Researchers find BPA and BPS affect embryonic brain development in zebrafish, eurekalert, 12-JAN-2015.
Low-dose exposure to bisphenol A and replacement bisphenol S induces precocious hypothalamic neurogenesis in embryonic zebrafish, pnas, January 12, 2015.
BPA alternative disrupts normal brain-cell growth, is tied to hyperactivity, study says, washingtonpost, January 12, 2015.
In this recent Korean study, adult zebrafish pairs were exposed to Bisphenol-S (BPS) for 3 weeks. A significant decrease of egg production in female fish and a significant decrease of testosterone concentration in male fish were observed.
While bisphenol S (BPS) has been frequently detected both in environment and biota, limited information is available on its effects on endocrine system. In the present study, adult zebrafish pairs were exposed to 0.5, 5, and 50 μg/L of BPS for 21 d, and the effects on reproduction, sex hormones, and transcription of the genes belonging to hypothalamic-pituitary-gonad (HPG) axis were investigated. Adverse effects on performances of F1 generation were further examined with or without subsequent exposure to BPS. Egg production and the gonadosomatic index in female fish were significantly decreased at ≥0.5 μg/L BPS. Plasma concentrations of 17β-estradiol were significantly increased in both male and female fish. In male fish, however, significant decreases of testosterone concentration were observed along with up-regulation of cyp19a, and down-regulation of cyp17 and 17βhsd transcripts. Parental exposure to BPS resulted in delayed and lesser rates of hatching even when they were hatched in control water. Continuous BPS exposure in F1 embryos resulted in worse hatchability and increased malformation rates compared to those without BPS exposure. Our observations showed that exposure to low level BPS could affect the feedback regulation of HPG axis of zebrafish and impair the hatching and development of its offspring.
Bisphenol S Disrupts Estradiol-Induced Nongenomic Signaling in a Rat Pituitary Cell Line: Effects on Cell Functions
Just like the controversial Bisphenol A that it designed to replace, Bisphenol S chemical used in cash register receipts and other consumer products messes with hormones, according to research by University of Texas scientists. The study is the first to link low concentrations of BPS – a BPA alternative – to disruption of estrogen, spurring concern that it might harm human health. Researchers exposed rat cells to levels of BPS that are within the range people are exposed to…. and, just like BPA, the compound interfered with how cells respond to natural estrogen, which is vital for reproduction and other functions.
Chemical Deception: Multiple Forms of Hormone-Disrupting Bisphenol Found In US Food Supply
You know about the dangers of Bisphenol A (BPA), and hopefully Bisphenol S (BPS), but did you know that there are at least eight toxic bisphenols in our food supply, with 75% of food samples from the US tested showing significant levels of these ubiquitous poisons?
Human fertility under attack : From research to action on phthalates and endocrine disrupting chemicals
Non-communicable diseases currently represent a leading threat to human health and human development and pose one of the key challenges of the 21st century.
Video by RESenvsante, April 10th, 2012, Paris, Assemblée Nationale colloquium on EDCs – focus on phtalates and fertility, starring Shanna Swan
Today, endocrine disruptors constitute a key to understanding how prevention can be better applied on those diseases and how their progression can consequently be halted. It is a matter of urgency and we must act immediately by devoting a higher amount of resources to research, by upgrading healthcare practices, by developing regulatory as well as economic tools and providing safer alternatives to endocrine disruptors.