Endocrine-disrupting effects of thioxanthone photoinitiators

Nail salon dust reveals alarmingly high photoinitiator levels: Assessing occupational risks

Photoinitiators (PIs) are chemical additives that generate active substances, such as free radicals to initiate photopolymerization. Traditionally, polymerization has been considered a green technique that seldomly generates contaminants. However, many researches have confirmed toxicity effects of PIs, such as carcinogenicity, cytotoxicity, endocrine disrupting effects. Surprisingly, we found high levels of PIs in indoor dust. Our analysis revealed comparable levels of PIs in dust from printing shops (geometric mean, GM: 1.33 ×103 ng/g) and control environments (GM: 874 ng/g), underscoring the widespread presence of PIs across various settings. Alarmingly, in dust samples from nail salons, PIs were detected at total concentrations ranging from 610 to 1.04 × 107 ng/g (GM: 1.87 ×105 ng/g), significantly exceeding those in the control environments (GM: 1.43 ×103 ng/g). Nail salon workers' occupational exposure to PIs through dust ingestion was estimated at 4.86 ng/kg body weight/day. Additionally, an in vitro simulated digestion test suggested that between 10 % and 42 % of PIs present in ingested dust could become bioaccessible to humans. This is the first study to report on PIs in the specific environments of nail salons and printing shops. This study highlights the urgent need for public awareness regarding the potential health risks posed by PIs to occupational workers, marking an important step towards our understanding of environmental pollution caused by PIs.

A review on takeaway packaging waste: Types, ecological impact, and disposal route

Rapid economic growth and urbanization have led to significant changes in the world's consumption patterns. Accelerated urbanization, the spread of the mobile Internet, and the increasing pace of work globally have all contributed to the demand for the food takeaway industry. The rapid development of the takeaway industry inevitably brings convenience to life, and with it comes great environmental pressure from waste packaging materials. While maintaining the convenience of people's lives, further reducing the environmental pollution caused by takeaway packaging materials and promoting the recycling and reuse of takeaway packaging waste need to attract the attention and concern of the whole society. This review systematically and comprehensively introduces common takeaway food types and commonly used packaging materials, analyzes the impacts of discarded takeaway packaging materials on human health and the ecological environment, summarizes the formulation and implementation of relevant policies and regulations, proposes treatment methods and resourceful reuse pathways for discarded takeaway packaging, and also provides an outlook on the development of green takeaway packaging. Currently, only 20% of waste packaging materials are recycled worldwide, and there is still a need to develop more green takeaway packaging materials and continuously improve relevant policies and regulations to promote the sustainable development of the takeaway industry. The review is conducive to further optimizing the takeaway packaging management system, alleviating the environmental pollution problem, and providing feasible solutions and technical guidance for further optimizing takeaway food packaging materials and comprehensive utilization of resources.

Occurrence, Fate, Human Exposure, and Toxicity of Commercial Photoinitiators

Photoinitiators (PIs) are a family of anthropogenic chemicals used in polymerization systems that generate active substances to initiate polymerization reactions under certain radiations. Although polymerization is considered a green method, its wide application in various commercial products, such as UV-curable inks, paints, and varnishes, has led to ubiquitous environmental issues caused by PIs. In this study, we present an overview of the current knowledge on the environmental occurrence, human exposure, and toxicity of PIs and provide suggestions for future research based on numerous available studies. The residual concentrations of PIs in commercial products, such as food packaging materials, are at microgram per gram levels. The migration of PIs from food packaging materials to foodstuffs has been confirmed by more than 100 reports of food contamination caused by PIs. Furthermore, more than 20 PIs have been detected in water, sediment, sewage sludge, and indoor dust collected from Asia, the United States, and Europe. Human internal exposure was also confirmed by the detection of PIs in serum. In addition, PIs were present in human breast milk, indicating that breastfeeding is an exposure pathway for infants. Among the most available studies, benzophenone is the dominant congener detected in the environment and humans. Toxicity studies of PIs reveal multiple toxic end points, such as carcinogenicity and endocrine-disrupting effects. Future investigations should focus on synergistic/antagonistic toxicity effects caused by PIs coexposure and metabolism/transformation pathways of newly identified PIs. Furthermore, future research should aim to develop "greener" PIs with high efficiency, low migration, and low toxicity.

Distribution characteristics of photoinitiators and their flux estimation from the Pearl River Delta to the coastal waters of the South China Sea

Photoinitiators (PIs) are widely used in industrial polymerization processes. It has been reported that PIs are ubiquitous in indoor environments and that humans are exposed to PIs, but the occurrence of PIs in natural environments are rarely known. In the present study, 25 PIs, including 9 benzophenones (BZPs), 8 amine co-initiators (ACIs), 4 thioxanthones (TXs) and 4 phosphine oxides (POs), were analyzed in water and sediment samples collected from eight riverine outlets of the Pearl River Delta (PRD). Eighteen, 14, and 14 of the 25 target PIs were detected in water, suspended particulate matter (SPM) and sediment samples, respectively. The total concentrations of PIs in water, SPM, and sediment were in the ranges of 2.88‒96.1 ng/L, 9.25‒923 ng/g dry weight (dw), and 3.79‒56.9 ng/g dw, with geometric mean concentration (GM) of 10.8 ng/L, 48.6 ng/g dw, and 17.1 ng/g dw, respectively. A significant linear regression was observed between the log partitioning coefficients (K_d) values of PIs and their log octanol water partition coefficient (K_ow) values (R² = 0.535, p < 0.05). The annual riverine input of PIs to the coastal waters of the South China Sea via eight main outlets of the PRD was estimated to be 4.12 × 10³ kg/year, and the ∑BZPs, ∑ACIs, ∑TXs and ∑POs contributed to 1.96 × 10³, 1.24 × 10³, 89.6 and 830 kg/year, respectively. This is the first report of a systematic description of the occurrence characteristics of PIs exposure in water, SPM, and sediment. The environmental fate and risks of PIs in aquatic environments need further investigations.

Three photoinitiators induce breast tumor growth in mouse xenografts with MCF-7 breast cancer cells

Photoinitiators are utilized in the production of a wide range of commonly used products. However, some photoinitiators exert toxic effects. We previously demonstrated the endocrine-disrupting effects of photoinitiators in vitro. The present study investigated the estrogenic activities of three photoinitiators: 1-hydroxycyclohexyl phenyl ketone (1-HCHPK), methyl 2-benzoylbenzoate (MBB), and 2-methyl-4'-(methylthio)-2-morpholinopropiophenone (MTMP), which were subcutaneously injected into mouse xenografts with MCF-7 breast cancer cells. The results obtained showed that 1-HCHPK, MBB, and MTMP promoted breast tumor growth in these xenografts. A pretreatment with the estrogen receptor antagonist tamoxifen blocked the tumor growth-promoting effects of each photoinitiator. Collectively, the present results suggest that the three photoinitiators exhibit estrogenic agonist activities in vivo. Furthermore, as a factor for breast tumor growth, these photoinitiators potentially have estrogenic properties in vivo.

Cytotoxic and cytocompatible comparison among seven photoinitiators-triggered polymers in different tissue cells

Photoinitiators (PIs) are widely used for photopolymerization in industrial area and recently paid close attention to in biomedical field. However, there are few reports on their toxicity to human health. Here we explored cytotoxicity and cytocompatibilty of seven commercial and industrial-used PIs for developing their potential clinical application. Phenylbis(acyl) phosphine oxides (BAPO), 2-Benzyl-2-(dimethylamino)-4'-morpholinobutyrophenone (369), 4,4'-Bis(diethylamino) benzophenone (EMK), Diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide (TPO), and 2-Isopropylthioxanthone (ITX) caused different extent cytotoxicities to four tissue types of cells at the concentrations of 1 to 50 μM under a non-irradiation condition, of which the BAPO cytotoxicity was the highest, whereas Ethyl (2,4,6-trimethylbenzoyl) phenylphosphinate (TPOL) and Methyl benzoylformate (MBF) displayed the lowest cellular toxicity. The cell lines and primary cells appeared highly sensitive to BAPO toxicity, the primary lymphocytes relatively to photoinitiator 369 (369) and EMK toxicities, LO2 cells to EMK and TPO toxicities, the primary lymphocytes and HUVEC-12 cells to MBF toxicity, but only HEK293T cells not to 369 toxicity. Furthermore, these PIs led to increasing cytotoxicity to different extents after exposure to 455 nm blue light, which is consistent with non-irradiation tendency. All the cells presented low sensitivity to TPOL and MBF, of which TPOL-triggered polymer is dramatically superior in its cytocompatibility to MBF, and in its transparency to clinically exclusively-used camphorquinone (CQ). The novel findings indicate that BAPO is the most toxic among the seven PIs, but TPOL and MBF are the least toxic, directing their development and application. Combined their triggered polymer cytocompatibility and color with reported deep curing efficiency, TPOL is more promising to be applied especially to clinical practice.

Determination of 21 photoinitiators in human plasma by using high-performance liquid chromatography coupled with tandem mass spectrometry: A systemically validation and application in healthy volunteers

In the present study, a comprehensive and sensitive method for simultaneous determination of 21 PIs (nine benzophenones, eight amine co-initiators, and four thioxanthones) in human plasma using high-performance liquid chromatography coupled with tandem mass spectrometry was developed and validated. Two different pre-treatment approaches (liquid-liquid extraction (LLE) and LLE coupled with solid-phase extraction (SPE)) and eight extraction solvents were studied to optimize sample treatment to obtain good recoveries and reduce any matrix effects. The procedure of LLE+SPE was selected as final sample treatment procedure because it obtained higher recoveries as well as lower matrix effects than that performed by LLE alone. The recoveries of 21 target analytes at three spiked concentrations (0.05, 0.5, and 5 ng/mL) ranged from 81% to 109%. The intra- and inter-day relative standard deviations were between 2.5% and 13%. Accuracy and precision data indicated that the detection method was accurate and precise for most of the PIs. The linearities of the labeled dilution calibration curves at 10 concentration levels (iLOQ to 100 ng/mL or iLOQ to 200 ng/mL) were good with correlation coefficients ranged from 0.995 to 0.999. The method quantification limits were in the range of 1.7-16 pg/mL. The analytical method was applied to the analysis of PIs in 14 human plasma samples collected from pregnant women in Guangdong Province, China. Fifteen PIs were detected with total concentrations ranging from 318 to 2772 pg/mL. The ubiquitous contamination of human plasma with PIs suggests that there is widespread exposure to these compounds. Consequently, there should be increased awareness of these pollutants in the environment.

Occurrence of multiple classes of emerging photoinitiators in indoor dust from E-waste recycling facilities and adjacent communities in South China and implications for human exposure

Photoinitiators (PIs) are indispensable additives in photopolymerization. PI-containing consumables, such as adhesives, coatings, UV-cured inks and light-sensitive materials, are widely used in various electronic products. Nevertheless, there is no information concerning the identification of PIs as emerging contaminants from e-waste recycling. In this study, 25 PIs, including 9 benzophenones (BZPs), 8 amine coinitiators (ACIs), 4 thioxanthones (TXs) and 4 phosphine oxides (POs), were analyzed in indoor dust from typical e-waste recycling facilities and adjacent rural communities, as well as from control urban communities. All 25 target PIs were detected in e-waste dust, while only 17 and 15 of the 25 target PIs were detected in local home dust and urban home dust, respectively. The PIs detected in all dust samples were dominated by BZPs and POs, followed by ACIs and TXs. Most PIs exhibited significantly higher levels in e-waste dust than local or urban home dust. The influence of PI contamination on the local household environment by dust diffusion and transport from near e-waste recycling facilities may be lower due to the low volatility of most PIs. Characteristic composition profiles of PIs for indoor dust from the e-waste recycling area were identified and compared to those from the control area. Significant correlations were found among almost all the frequently detected PIs in the e-waste dust, indicating their similar application in electronic products and common emission from e-waste recycling. The estimated daily intakes of PIs via dust ingestion for the e-waste dismantling workers, as determined by using Monte Carlo analysis, were several times higher than those for the local adult residents and the general urban adult residents, which should be an emerging concern. To the best of our knowledge, this is the first report showing that e-waste dismantling/recycling activities lead to largely common releases of a wide range of multiple classes of PIs.

Cytotoxic effects of thioxanthone derivatives as photoinitiators on isolated rat hepatocytes

Thioxanthone and its analogues, 2- or 4-isopropylthioxanthone, 2-chlorothioxanthone, 2,4-diethylthioxanthone (DETX) and xanthone, are used as photoinitiators of ultraviolet (UV) light-initiated curable inks. As these photoinitiators were found in numerous food/beverage products packaged in cartons printed with UV-cured inks, the cytotoxic effects and mechanisms of these compounds were studied in freshly isolated rat hepatocytes. The toxicity of DETX was greater than that of other compounds. DETX elicited not only concentration (0-2.0 mm)- and time (0-3 hours)-dependent cell death accompanied by the depletion of cellular adenosine triphosphate (ATP), and reduced glutathione (GSH) and protein thiol levels, but also the accumulation of GSH disulfide and malondialdehyde. Pretreatment of hepatocytes with either fructose at a concentration of 10 mm or N-acetyl-l-cysteine (NAC) at a concentration of 5.0 mm ameliorated DETX (1 mm)-induced cytotoxicity. Further, the exposure of hepatocytes to DETX resulted in the induction of reactive oxygen species (ROS) and loss of mitochondrial membrane potential, both of which were partially prevented by the addition of NAC. These results indicate that: (1) DETX-induced cytotoxicity is linked to mitochondrial failure and depletion of cellular GSH; (2) insufficient cellular ATP levels derived from mitochondrial dysfunction were, at least in part, ameliorated by the addition of fructose; and (3) GSH loss and/or ROS formation was prevented by NAC. Taken collectively, these results suggest that the onset of toxic effects caused by DETX may be partially attributable to cellular energy stress as well as oxidative stress.

Occurrence and Distribution of Photoinitiator Additives in Paired Maternal and Cord Plasma in a South China Population

Photoinitiators (PIs) are widely used in industrial polymerization and have been detected as emerging contaminants in environmental matrixes. It has been reported that humans are exposed to PIs, but the maternal-fetal transmission of PIs has not been documented. In this study, we analyzed 21 PIs (9 benzophenones, BZPs; 8 amine co-initiators, ACIs; and 4 thioxanthones, TXs) in matched maternal-cord plasma samples from 49 pregnant women in South China. Sixteen of the 21 target PIs were found in maternal plasma at concentrations of ∑PIs (sum of the detected PIs) from 303 to 3500 pg/mL. Meanwhile, 12 PIs were detected in cord plasma with ∑PIs from 104 to 988 pg/mL. The PIs detected in both maternal and cord plasma samples were dominated by BZPs, followed by ACIs and TXs. Different groups of PIs showed structure-dependent placental transfer efficiencies (PTEs). The PTEs were generally less than 100% for BZPs but greater than 100% for ACIs and TXs. By further theoretical calculation, we revealed the critical structural features of PIs that affect PTEs. This is the first study to investigate the occurrence and distribution of PIs in paired maternal and cord plasma, and it sheds light on the potential mechanism of structure-dependent placental transfer.

Identification of Photoinitiators, Including Novel Phosphine Oxides, and Their Transformation Products in Food Packaging Materials and Indoor Dust in Canada

Although photopolymerization is generally considered a green technology, the contamination of foodstuffs by photoinitiators (PIs), an essential component of photopolymerization systems, has recently attracted notice. Despite this interest, little attention has been paid to PI contamination in the environment. To date, only one study, performed in China, has reported the occurrence of PIs in the environment. In the present study, the occurrence of 25 PI additives with discrete molecular structures was investigated in food packaging materials and indoor dust. The PIs studied here include benzophenones (BZPs), thioxanthones (TXs), amine co-initiators (ACIs), and novel phosphine oxides (POs). Twenty-four PIs were detected in food packaging materials. Total concentrations of PIs (∑PIs) ranged between 122 and 44 113 ng/g, with a geometric mean (GM) of 3375 ng/g. The photodegradation of PIs in food packaging materials was investigated for the first time, and the half-lives of PIs in these materials were found to range from 32 to 289 h. These 24 PIs were also detected in indoor dust samples (GM of ∑PIs = 1483 ng/g). The relative abundances of different PIs were found to vary between the packaging materials and the indoor dust, which is attributed in part to the different stabilities of different PIs under simulated sunlight. Using standards synthesized in our lab, four TX transformation products (GM: 34.8 ng/g) were also detected in indoor dust. The concentrations of the transformation products were higher than the concentrations of the parent chemicals in indoor dust. Thus, further studies exploring human exposure to TXs should include these transformation products to avoid underestimation. This is the first report of PIs and relevant transformation products in the indoor environment in North America.

Metabolic Susceptibility of 2-Chlorothioxanthone and Its Toxic Effects on mRNA and Protein Expression and Activities of Human CYP1A2 and CYP3A4 Enzymes

Thioxanthones (TXs) are photoinitiators widely used in UV curable resins and food packaging, and their residues have been frequently detected in human bodies. Our current understanding of the susceptibility of residual TXs to metabolism and their effects on human health is very limited. The in vitro metabolism of TXs and its toxic effects on cytochrome P450 (CYP) (the key xenobiotic metabolizing enzymes) were examined in this study. 2-Chlorothioxanthone (2-Cl-TX) significantly inhibited the enzymatic activities of CYP1A2 and CYP3A4 with IC₅₀ of 8.36 and 0.86 μM, respectively. The exposure to 2-Cl-TX at 2.5 μM up-regulated the mRNA expression of CYP1A2 and CYP3A4 in human hepatocellular carcinoma cells to 3.03-fold and 2.02-fold, respectively. 2-Cl-TX at 2.5 μM caused 2.19-fold and 1.98-fold overexpression of CYP1A2 and CYP3A4, respectively. In vitro studies revealed that 2-Cl-TX was biotransformed into two metabolites through the sulfoxidation of the sulfur atom, or via the hydroxylation of aromatic carbon. Results from this study, including the metabolic susceptibility of residual 2-Cl-TX, the proposed metabolites and the significant toxic effect on the activities, mRNA, and protein expression of CYP1A2 and CYP3A4, are vital to the human health and safety risk assessment from this ubiquitous xenobiotic.

First Detection of Photoinitiators and Metabolites in Human Sera from United States Donors

Photoinitiators (PIs), including benzophenones (BZPs), thioxanthones (TXs), and amine co-initiators (ACIs), are commonly used in photopolymerization systems, and their contamination in foodstuffs and the environment is attracting attention. Although humans are likely exposed to PIs, no data on human burdens of these chemicals are available. In this study, 18 PIs were detected in 50 individual human serum samples with concentrations of ΣPIs (sum of the detected PIs) from 423 to 2870 pg/mL (geometric mean, GM: 836 pg/mL). ΣBZPs (231-1240 ng/g,; GM: 593 pg/mL) were the dominant components, while ΣTXs (21.0-1431 ng/g; GM: 145 pg/mL) and ΣACIs (11.3-976 ng/g; GM: 48.5 pg/mL) were much lower. Data analysis found significantly higher concentrations of most PIs in the male sera than in the female ( p < 0.05). ΣPIs (2921-4139 ng/g; GM: 3621 pg/mL) were also detected in five pooled serum samples, each from at least 1000 donors, indicating the prevalent human burdens of PIs in a large population. Human liver S9 biodegradations of representative PIs, 2-isopropylthioxanthone (2-ITX) and 2,4-diethylthioxanthone (DETX), were conducted. Hydroxylation, sulfoxide, and sulfone metabolites of DETX and 2-ITX were identified by high resolution mass spectrometry in human liver S9 incubation systems. With synthesized standards, the sulfoxide and sulfone metabolites were successfully detected in the human serum samples, which contributed substantially to total human burdens. The ubiquitous presence of PIs in human sera indicates significant human exposure to PIs, although photopolymerization reaction has been generally considered a green technology.

UV-irradiated 2-methyl-4'-(methylthio)-2-morpholinopropiophenone-containing injection solution produced frameshift mutations in the Ames mutagenicity assay

In previous studies, we detected the photoinitiators 1-hydroxycyclohexyl phenyl ketone (1-HCHPK), methyl 2-benzoylbenzoate (MBB), and 2-methyl-4'-(methylthio)-2-morpholinopropiophenone (MTMP) in intravenous injection solutions. In addition, we reported that 1-HCHPK, MBB, and MTMP exhibited cytotoxicity towards normal human peripheral blood mononuclear cells. A previous in vitro study reported that a free-radical photoinitiator introduced covalently bound purine residues into DNA. However, little is known about the in vitro mutagenicity of 1-HCHPK, MBB, and MTMP. In the present in vitro study, we evaluated the mutagenicity of 1-HCHPK, MBB, and MTMP using the Ames test. We found that untreated 1-HCHPK, MBB, and MTMP were not mutagenic in S. typhimurium strain TA97, TA98, TA100, TA102, or TA1535, regardless of the presence/absence of S9 activation. However, ultraviolet (UV) light-irradiated MTMP exhibited mutagenicity in S. typhimurium strain TA97 in the absence of S9 activation. In conclusion, we suggest that exposure to UV-irradiated MTMP, including in intravenous injection solutions, can result in frameshift mutations.

In silico prediction and in vivo analysis of antiestrogenic potential of 2-isopropylthioxanthone (2-ITX) in juvenile goldfish (Carassius auratus)

Previous studies have shown both anti-estrogenic and anti-androgenic activities of 2-isopropylthioxanthone (2-ITX), a well known food contaminant, in in vitro assays. However, no data are available on the anti-estrogenic potentials and risks of 2-ITX in aquatic organisms. This work evaluated the potential endocrine disrupting effects of 2-ITX at the level of estrogen receptor (ER) signaling cascade using juvenile goldfish (Carassius auratus) as model. Firstly, we investigated the ligand binding efficiency of 2-ITX to the ligand binding domains (LBD) of goldfish ER subtypes using a molecular docking approach. Secondly, we assessed the effects of 2-ITX on E2-induced hepatic expression of ERα1, ERβ1, ERβ2, and vitellogenin (VTG) in vivo. Crosstalk between ER-VTG and aryl hydrocarbon receptor 2 (AhR2)-cytochrome P4501A (CYP1A) was also investigated. Fish were injected with increasing doses of 2-ITX ranging from 2 to 10µg/g BW, and results were compared to the effect of tamoxifen, a well-known ER modulator. We observed that compared to ERβ, the interaction potentials of 2-ITX to goldfish ERα1 LBD was more stable in the inactive receptor conformation. The in silico docking simulation analysis also revealed that 2-ITX acted as agonist for the goldfish AhR2 LBDs suggesting the ability of this compound to activate the cross-talk between the ERα- and AhR-signaling pathways. In vivo experiments confirm in silico simulation predictions demonstrating that 2-ITX reduced the estrogenicity of E2 at both transcriptional and post-transcriptional levels, indicating a clear anti-estrogenic effect. Co-exposure of E2 and 2-ITX also resulted in a significant decrease of CYP1A gene expression with respect to 2-ITX alone. Results from these studies collectively revealed that the antiestrogenic property of 2-ITX can be ascribed to a combination of effects on multiple signaling pathways suggesting the potential for this environmental contaminant to affect the hormonal control of reproductive processes in fish.

Disruption of steroidogenesis: Cell models for mechanistic investigations and as screening tools

In the modern world, humans are exposed during their whole life to a large number of synthetic chemicals. Some of these chemicals have the potential to disrupt endocrine functions and contribute to the development and/or progression of major diseases. Every year approximately 1000 novel chemicals, used in industrial production, agriculture, consumer products or as pharmaceuticals, are reaching the market, often with limited safety assessment regarding potential endocrine activities. Steroids are essential endocrine hormones, and the importance of the steroidogenesis pathway as a target for endocrine disrupting chemicals (EDCs) has been recognized by leading scientists and authorities. Cell lines have a prominent role in the initial stages of toxicity assessment, i.e. for mechanistic investigations and for the medium to high throughput analysis of chemicals for potential steroidogenesis disrupting activities. Nevertheless, the users have to be aware of the limitations of the existing cell models in order to apply them properly, and there is a great demand for improved cell-based testing systems and protocols. This review intends to provide an overview of the available cell lines for studying effects of chemicals on gonadal and adrenal steroidogenesis, their use and limitations, as well as the need for future improvements of cell-based testing systems and protocols.

Observation of Emerging Photoinitiator Additives in Household Environment and Sewage Sludge in China

Photoinitiators (PIs) are widely used additives in industrial polymerization process, the contamination of which through migration into foodstuffs has been subjected to increasing public scrutiny. Nevertheless, little attention has been paid to the PI residue levels and potential exposure pathways from other environmental compartments. In the present study, the occurrence of PI additives with discrete molecular structures, that is, nine benzophenones (BZPs), four thioxanthones (TXs), and eight amine co-initiators (ACIs), was investigated in commercial products, indoor dust and sewage sludge samples. Nine PI compounds were positively detected in ultraviolet curable resins with concentrations of ∑PIs (sum of the detected PIs) up to 2.51 × 10(4) ng/g, and 20 PIs can be found in food contact materials with concentrations of ∑PIs varying from 65.9 to 6.93 × 10(3) ng/g. The wide usage of PIs in commercial products led to the occurrence of 19 PIs in indoor dust, with concentrations of ∑PIs in the range of 245-5.68 × 10(3) ng/g. Meanwhile, all 21 targeted PIs could be identified in the sewage sludge, with concentrations from 67.6 to 2.03 × 10(3) ng/g. Distinct PI composition profiles were observed in different investigated compartments, and BZPs were the dominant homologues in all samples. Most of the target PIs were further identified as class III chemicals by toxic hazard estimation algorithm (Toxtree), which indicates the compounds might be of significant toxicity or have reactive functional groups.

Adrenocortical endocrine disruption

The adrenal has been neglected in endocrine disruption regulatory testing strategy. The adrenal is a vital organ, adrenocortical insufficiency is recognised in life threatening "adrenal crises" and Addison's disease, and the consequences of off-target toxicological inhibition of adrenocortical steroidogenesis is well recognised in clinical medicine, where drugs such as aminoglutethimide and etomidate killed patients via unrecognised inhibition of adrenocortical steroidogenic enzymes (e.g. CYP11B1) along the cortisol and aldosterone pathways. The consequences of adrenocortical dysfunction during early development are also recognised in the congenital salt wasting and adrenogenital syndromes presenting neonatally, yet despite a remit to focus on developmental and reproductive toxicity mechanisms of endocrine disruption by many regulatory agencies (USEPA EDSTAC; REACH) the assessment of adrenocortical function has largely been ignored. Further, every step in the adrenocortical steroidogenic pathway (ACTH receptor, StAR, CYP's 11A1, 17, 21, 11B1, 11B2, and 3-hydroxysteroid dehydrogenase Δ4,5 isomerase) is known to be a potential target with multiple examples of chemicals inhibiting these targets. Many of these chemicals have been detected in human and wildlife tissues. This raises the question of whether exposure to low level environmental chemicals may be affecting adrenocortical function. This review examines the omission of adrenocortical testing in the current regulatory frameworks; the characteristics that make the adrenal cortex particularly vulnerable to toxic insult; chemicals and their toxicological targets within the adrenocortical steroidogenic pathways; the typical manifestations of adrenocortical toxicity (e.g. human iatrogenically induced pharmacotoxicological adrenal insufficiency, manifestations in typical mammalian regulatory general toxicology studies, manifestations in wildlife) and models of adrenocortical functional assessment. The utility of the in vivo ACTH challenge test to prove adrenocortical competency, and the H295R cell line to examine molecular mechanisms of steroidogenic pathway toxicity, are discussed. Finally, because of the central role of the adrenal in the physiologically adaptive stress response, the distinguishing features of stress, compared with adrenocortical toxicity, are discussed with reference to the evidence required to claim that adrenal hypertrophy results from stress rather than adrenocortical enzyme inhibition which is a serious adverse toxicological finding. This article is part of a special issue entitled 'Endocrine disruptors and steroids'.

Disruption of endocrine function in H295R cell in vitro and in zebrafish in vivo by naphthenic acids

Oil sands process-affected water (OSPW) have been reported to exhibit endocrine disrupting effects on aquatic organisms. Although the responsible compounds are unknown, naphthenic acids (NAs) have been considered to be implicated. The current study was designed to investigate the endocrine disruption of OSPW extracted NAs (OS-NAs) and commercial NAs (C-NAs) using a combination of in vitro and in vivo assays. The effects of OS-NAs and C-NAs on steroidogenesis were assessed both at hormone levels and expression levels of hormone-related genes in the H295R cells. The transcriptions of biomarker genes involved in endocrine systems in zebrafish larvae were investigated to detect the effects of OS-NAs and C-NAs on endocrine function in vivo. Exposure to OS-NAs and C-NAs significantly increased production of 17β-estradiol (E2) and progesterone (P4), and decreased production of testosterone (T). Both OS-NAs and C-NAs significantly induced the expression of several genes involved in steroidogenesis. The abundances of transcripts of biomarker gene CYP19b, ERα, and VTG were significantly up-regulated in zebrafish larvae exposed to OS-NAs and C-NAs, which indicated that NAs had negative effects on estrogen-responsive gene transcription in vivo. These results indicated that NAs should be partly responsible for the endocrine disrupting effects of OSPW.

Extended evaluation on the ES-D3 cell differentiation assay combined with the BeWo transport model, to predict relative developmental toxicity of triazole compounds

The mouse embryonic stem D3 (ES-D3) cell differentiation assay is based on the morphometric measurement of cardiomyocyte differentiation and is a promising tool to detect developmental toxicity of compounds. The BeWo transport model, consisting of BeWo b30 cells grown on transwell inserts and mimicking the placental barrier, is useful to determine relative placental transport velocities of compounds. We have previously demonstrated the usefulness of the ES-D3 cell differentiation assay in combination with the in vitro BeWo transport model to predict the relative in vivo developmental toxicity potencies of a set of reference azole compounds. To further evaluate this combined in vitro toxicokinetic and toxicodynamic approach, we combined ES-D3 cell differentiation data of six novel triazoles with relative transport rates obtained from the BeWo model and compared the obtained ranking to the developmental toxicity ranking as derived from in vivo data. The data show that the combined in vitro approach provided a correct prediction for in vivo developmental toxicity, whereas the ES-D3 cell differentiation assay as stand-alone did not. In conclusion, we have validated the combined in vitro approach for developmental toxicity, which we have previously developed with a set of reference azoles, for a set of six novel triazoles. We suggest that this combined model, which takes both toxicodynamic and toxicokinetic aspects into account, should be further validated for other chemical classes of developmental toxicants.

[Development of injection containers for patient and medical staff]

Recently, there has been a transition from glass to plastic injection containers in Japan. In our previous study, we suggested that plastic containers had less impurity contamination than glass containers. However, the use of some plasticizers has been limited because of their endocrine disrupting effects. Therefore, contamination has been a concern due to chemicals in injection solution packed with plastic containers. Indeed, in our recent study, photoinitiators were detected in an injection solution coming from plastic containers. Photoinitiators mainly exist in ink. We therefore speculated that ink originating from a photoinitiator directly printing on plastic containers had migrated into the injection solutions. In a clinical setting, plastic containers are very tractable because they are lightweight and less breakable. On the other hand, from a safety view point, these containers may be hazardous because of permeation by steam, ambient air or photoinitiators. In the present symposium, we will discuss the risk of photoinitiators leaking into injection solution packed with plastic containers, and countermeasures to avoid this risk.

Photoinitiators enhanced 1,2-dichloropropane-induced cytotoxicity in human normal embryonic lung fibroblasts cells in vitro

Dichloromethane (DCM) and 1,2-dichloropsropane (DCP) have various uses, including being solvents for paint removers. Photoinitiators are also used in a wide range of commercial applications such as printing. These chemicals have been shown to induce cytotoxic effects. In the present study, we evaluated the combined effects of DCM or DCP from paint removers and photoinitiators used in printing on normal human embryonic lung fibroblasts with the aim of preventing occupational injuries. We showed that DCP, 2,2-dimethoxy-2-phenylacetophenone (2,2-DMPAP), 2-ethylhexyl-4-(dimethylamino) benzoate (2-EHDAB), 1-hydroxycyclohexyl phenyl ketone (1-HCHPK), and methyl 2-benzoylbenzoate (MBB) induced cytotoxicity, whereas DCM and 2-isopropylthioxanthone (2-ITX) did not. In addition, 2-methyl-4'-(methylthio)-2-morpholinopropiophenone (MTMP) caused a slight increase in cytotoxicity. The combination of DCP and the four photoinitiators (2,2-DMPAP, 2-EHDAB, MBB, and MTMP) significantly induced cytotoxicity and also led to apoptosis. In conclusion, the combination of DCP and photoinitiators may increase the risk of respiratory diseases.