Bernard Robaire

Flame retardants are a diverse class of environmental contaminants widely used to reduce flammability in consumer products, leading to pervasive human exposure. Among these, polybrominated flame retardants (PBFRs), including polybrominated diphenyl ethers (PBDEs), and organophosphate ester flame retardants (OPEs) have raised significant concern due to their potential to disrupt reproductive health. Increasing experimental, epidemiological, and mechanistic evidence demonstrates that both PBDEs and OPEs adversely affect both the male and female reproductive systems. In males, exposure to these compounds is associated with impaired spermatogenesis, altered sperm quality, disrupted steroidogenesis, and structural and functional damage to the testis. Mechanistic studies reveal direct toxicity to Leydig, Sertoli, and germ cells, driven by mitochondrial dysfunction, oxidative stress, endocrine disruption, and cytoskeletal disorganization that may compromise both fertility and offspring health. In females, PBDEs and OPEs disrupt ovarian folliculogenesis, steroid hormone synthesis, and oocyte quality, while also altering uterine receptivity. These effects are mediated through perturbations of the hypothalamic–pituitary–gonadal axis, interference with nuclear and membrane hormone receptors, mitochondrial injury, oxidative stress, and dysregulation of signaling pathways essential for follicle maturation and ovulation. Both classes of flame retardants can bioaccumulate and cross critical biological barriers, including the placenta, raising concerns about developmental and transgenerational effects. Collectively, the evidence underscores that PBFRs and OPEs pose significant risks to reproductive function in both sexes, acting through molecular mechanisms that disrupt gonadal development, endocrine signaling, and cellular homeostasis. Understanding these shared and sex-specific pathways is essential for improving human health risk assessment and guiding regulatory strategies.

Organophosphate esters (OPEs), widely used as flame retardants and plasticizers, are environmental toxicants known to disrupt lipid metabolism. Although most studies have focused on individual OPEs, environmental exposures typically involve complex mixtures. Our previous studies demonstrated that a representative OPE mixture from Canadian household dust promotes cholesterol and lipid droplet accumulation in THP-1 macrophages. However, the molecular mechanisms underlying this lipid dysregulation remain unclear. Here, we employed tandem mass tag (TMT)-based quantitative proteomics to investigate how OPE mixtures alter protein expression and lipid regulation in macrophages. THP-1 macrophages were exposed to vehicle or environmentally relevant dilutions of the OPE mixture for 48 h. Lysates were subjected to TMT labeling and mass spectrometry. Bioinformatic analyses using STRING and Ingenuity Pathway Analysis identified 162 differentially expressed proteins, with unsupervised clustering highlighting cholesterol biosynthesis as a key pathway. Further validation via qPCR and upstream analysis implicated the sterol regulatory element-binding protein 2 (SREBP2) signaling axis in OPE-induced cholesterol biosynthesis. Functional assays revealed that atorvastatin-mediated HMG-CoA reductase inhibition, the rate limiting enzyme in cholesterol biosynthesis, prevents cholesterol buildup and lipid droplet formation in macrophages. These findings provide the first evidence that an environmentally relevant OPE mixture can induce cholesterol biosynthesis in human macrophages. These studies provide mechanistic evidence that an environmentally relevant mixture of organophosphate esters induces cholesterol biosynthesis in macrophages. These findings link real-world exposure to lipid pathways implicated in metabolic disease and support the need for updated regulatory standards that protect human health.

Organophosphate esters (OPEs), widely used as flame retardants and plasticizers, are frequently detected in indoor environments and human tissues, raising concerns about their potential endocrine-disrupting effects. In this study, we examined the effects of a household dust-based mixture of OPEs, along with two structural distinct sub-mixtures, on the phenotype, function, and lipidome on MA10 Leydig cells. Using high-content imaging, we identified increase in oxidative stress levels and accumulation of lipid droplets as common phenotypic effects across mixtures. Notably, the triaryl OPE sub-mixture exhibited greater potency, suggesting that specific structural features contribute to the toxicity of OPEs. While the OPE mixture did not impair basal steroid hormone production in MA-10 cells, changes were observed in stimulated progesterone levels and transcriptional regulation of key steroidogenic transcripts. When comparing lipidomic profiles across three steroidogenic cell lines (MA-10, H295R, and KGN), we found that glycerolipids, particularly triglycerides and diglycerides, consistently appeared to be the most affected lipid species, highlighting a common disruption in the composition of lipid droplet. However, cell line specific effects were also observed, especially in the regulation of cholesterol esters, likely reflecting differences in cholesterol sourcing and steroidogenic pathways. These findings emphasize the importance of evaluating environmentally relevant chemical mixtures and demonstrate that OPEs can disrupt steroidogenic function and lipid metabolism.

Organophosphate esters (OPEs), commonly used as flame retardants and plasticizers, are ubiquitous environmental contaminants, with high concentrations found in indoor house dust. Previously, we have reported that individual OPEs have adverse effects on HepG2 liver cells. However, real-world exposure involves mixtures of OPEs. In this study, we investigated the effects of an environmentally relevant mixture of OPEs, detected in Canadian house dust, on HepG2 cell phenotype and function. Using high-content imaging, we found that this mixture increased cytotoxicity and lipid droplet size, while lysosomes were the most effected endpoint. We used the DQ-BSA degradation assay to assess the function of lysosomes and confocal microscopy to confirm the status of lysosomal transcription factor EB (TFEB). We then tested lysosomal enzyme activities to determine potential downstream effects. OPE mixture induced concentration-dependent increases in the degradation capacity of lysosomes and elevated nuclear translocation of TFEB when compared to controls. Increased activities of downstream lysosomal acid lipase (LAL) and cathepsin B (CTSB) validated the activation of TFEB and its downstream effect of lysosome biogenesis. Together, these data demonstrate that exposure to an environmentally relevant OPE mixture adversely affects liver cell survival, phenotype, and lysosome functions, providing potential mechanistic insight into consequences of OPE exposure and increased risk of liver damage associated with disrupted lipid and lysosome homeostasis. This study also highlights the importance of evaluating real-world chemical exposures as mixtures rather than as individual compounds.

Concerns about the adverse effects of bisphenol A (BPA), a chemical used for the production of polycarbonate plastics, epoxy resins, and as a color developer in thermal papers, have led to an increase in the use of 4,4-sulfonyldiphenol (bisphenol S; BPS), bis(3-allyl-4-hydroxyphenyl) sulfone (TGSA), 4-hydroxyphenyl 4-isoprooxyphenylsulfone (D-8), [3-[(4-methylphenyl)sulfonylcarbamoylamino]phenyl] 4-methylbenzenesulfonate (Pergafast-201; PF-201), and 2,4-bis(phenylsulfonyl)phenol (DBSP) as alternative color developers. Data on these chemicals are scarce, and little is known about their potential toxicity. We determined the effects of BPS, TGSA, D-8, PF-201, and DBSP on the phenotype, function, and transcriptome of KGN human granulosa cells. Using high-content imaging, we observed that TGSA was the most cytotoxic compound tested, followed by D-8, DBSP, PF-201, and BPS. Although the effects of these compounds on lysosomes, mitochondria, and oxidative stress were minimal, TGSA, D-8, and PF-201 drastically increased the number and total area of lipid droplets compared with the control. RNA sequencing analyses revealed that TGSA and D-8 exposure differentially regulated 2,414 and 2,563 genes, respectively. PF-201 was the least transcriptionally active chemical, significantly affecting only 6 transcripts. The predominant effect of TGSA was the activation of pathways related to the extracellular matrix, whereas both TGSA and D-8 inhibited pathways involved in cell cycle regulation, DNA replication, and DNA repair. Such mechanisms may be underlying the cytotoxicity and lipid droplet accumulation observed in KGN cells. These data suggest that alternative color developers such as TGSA, D-8, and PF-201 act by different mechanisms and may not be responsible replacements for BPA and BPS in thermal papers.

Exposure to individual organophosphate esters (OPEs) has been linked to immune dysfunction. However, the effect of OPEs as environmentally relevant mixtures on the immune system remains poorly understood. This study examines how parental exposure to an OPE mixture impacts the immune status of Sprague-Dawley rats and their offspring. Sprague-Dawley rats were fed a control or OPE-supplemented diet containing 13 OPEs detected in >85% of Canadian homes. Only male offspring of OPE-exposed animals showed a significant reduction in CD43lowHis48hi splenic monocyte–macrophages. There were no significant changes in CD43lowHis48hi splenic monocyte–macrophages in the F0 generation or female offspring. However, the OPE mixture significantly altered serum cytokine levels in both sexes and generations, with females and offspring experiencing more pronounced changes. Notably, female progeny had elevated levels of chemokines associated with monocyte recruitment. In vitro follow-up studies revealed that the OPE mixture delays monocyte-to-macrophage transition and monocyte migration in both sexes. These results indicate that an environmentally relevant OPE mixture disrupts immune function by affecting monocyte recruitment and differentiation but does not reveal clear sex differences. However, when combined with cytokine findings, these results support a hypothesis that OPE exposure causes male-specific decreases in CD43lowHis48hi monocyte–macrophages that are absent in females due to compensatory inflammation. These studies demonstrate that an environmentally relevant mixture of OPEs can alter basal immune status in the offspring of exposed animals. This work will be useful for risk assessment studies and regulations protecting human health.

Human health depends on planetary health, and yet healthcare provision can have unintended consequences for the health of the planet. Emissions from the healthcare sector include greenhouse gases, air pollution and plastic pollution, alongside chemical contamination. Chemical pollution resulting in endocrine disruption has been associated with plastics, which are a source of concerning additives such as phthalates, bisphenols, perfluoroalkyl and polyfluoroalkyl substances, and flame retardants (all routinely found in healthcare products). Many endocrine-disrupting chemicals are persistent and ubiquitous in the environment (including water and food sources), with potential secondary harms for human health, including disrupting reproductive, metabolic and thyroid function. Here we review evidence-based strategies for mitigating environmental effects of healthcare delivery. We focus on what endocrinologists can do, including reducing demand for healthcare services through better preventative health, focusing on high-value care and improving sustainability of medical equipment and pharmaceuticals through adopting circular economy principles (including reduce, reuse and, as a last resort, recycle). The specific issue of endocrine-disrupting chemicals might be mitigated through responsible disposal and processing, alongside advocating for the use of alternative materials and replacing additive chemicals with those that have lower toxicity profiles, as well as tighter regulations. We must work to urgently transition to sustainable models of care provision, minimizing negative effects on human and planetary health.

The adrenal glands play crucial roles in regulating metabolism, blood pressure, immune system function, and response to stress through the secretion of hormones. Despite their critical functions, the adrenal glands are often overlooked in studies on the effects of potential toxicants. Research across human, animal, and in vitro studies has identified more than 60 compounds that can induce adrenocortical toxicity. These compounds, known as endocrine-disrupting chemicals (EDCs), are natural or synthetic substances that interfere with the endocrine system. This review aims to provide an overview of the effects of 4 major families of EDCs—flame retardants, bisphenols, phthalates, and microplastics—on the function of the adrenal glands. The PubMed database was searched for studies reporting the effects of the chemicals in these 4 families on the adrenal glands. There is clear evidence that the morphology and function of the adrenal gland are affected, particularly through disrupting the steroidogenic pathway. Additionally, some EDCs have been shown to exert transgenerational effects, raising further concerns about their long-term effect. However, most EDCs have not been thoroughly evaluated for their effects on the function of the adrenal glands, especially in human studies. Thus, developing regulatory testing guideline to include the adrenal glands in the screening of EDCs is urgently needed.

Given the ubiquitous presence of plastic products in daily life, human exposure to nanoplastics (NPs) is inevitable. Previous studies have suggested that exposure to polystyrene nanoplastics (PSNPs) may contribute to reproductive disorders; however, the underlying mechanism remains elusive. The goal of this study was to investigate the impact of PSNPs on KGN human ovarian granulosa cells. KGN cells were exposed to varying concentrations of PSNPs (0–400 μg/mL) for 48 h; alterations in cell survival and morphology were assessed to elucidate potential toxic effects. PSNPs were shown to enter KGN cells. Exposure to PSNPs did not induce significant changes in cytotoxicity, Calcein intensity, or active mitochondria levels in KGN cells. However, PSNP exposure did induce a dose-dependent increase in cytoplasmic vacuoles and an increase in total lysosome area and in the numbers of lipid droplets in KGN cells. Our findings provide compelling evidence that PSNPs can penetrate cell cytoplasm and induce toxicity, resulting in an elevation in the numbers of lysosomes and lipid droplets. This may represent one mechanism by which PSNPs exert damage on the reproductive system.

There is growing evidence that organophosphate esters (OPEs) can act as endocrine-disrupting chemicals. However, only a few studies have assessed the effects of OPE exposure on one of the most important endocrine glands in the body, the adrenal gland. Our aim was to test the effects of a mixture of OPEs detected in Canadian house dust on adrenal function in Sprague Dawley rats. Adult male and female rats (n = 15 per treatment group) were administered either a vehicle or an OPE mixture (0.048, 1.6, or 48 mg/kg bw/d) for 70 to 72 d via their diet. With OPE exposure, adrenal glands from male adult rats were reduced in weight, whereas those of female rats showed an increase in weight. This led us to investigate whether OPEs induce sex-specific effects on adrenal gland function and the mechanisms involved. Serum levels of two adrenal hormones, aldosterone and corticosterone, were decreased only in male serum samples. Serum levels of renin and adrenocorticotropic hormone, which regulate aldosterone and corticosterone synthesis, respectively, were assessed. Exposure to the OPE mixture decreased renin levels only in males. Serum biochemistry analysis revealed that triglycerides and LDL cholesterol levels were increased in males. Transcriptomic analysis revealed that the top affected pathways in male adrenal glands from all three treatment groups were related to potassium channels, which play a role in regulating aldosterone and corticosterone levels. The most affected pathways in female adrenal glands were related to cholesterol biosynthesis and immune functions. These results show that an environmentally relevant mixture of OPEs affects adrenal function and that these effects are sex specific.