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

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.

Biomonitoring of benzophenones in guano samples of wild bats in Poland

Benzophenones (BPs) are substances used in the production of sunscreens, cosmetics, and personal care products. However, there is a lack of knowledge of BPs in wild animals. Therefore, the study aimed to assess the concentration of selected BPs commonly used in the cosmetic industry in guano samples collected from 4 colonies of greater mouse-eared bats (Myotis myotis). Liquid chromatography with tandem mass spectrometry (LC-MS/MS) was used to determine guano concentrations of benzophenone 1 (BP-1), benzophenone 2 (BP-2), benzophenone 3 (BP-3) and benzophenone 8 (BP-8). BP-1 levels above the method quantification limit (MQL) were noted in 97.5% of samples and fluctuated from <0.1 ng/g to 259 ng/g (mean 41.50 ng/g, median 34.8). The second most common was BP-3, which fluctuated from <0.1 ng/g to 19 ng/g (mean 6.67 ng/g, median 5.05), and its levels higher than MQL were observed in 40% of samples. BP-2 and BP-8 concentrations did not exceed the method detection limit (0.04 ng/g) in any analyzed sample. There were visible differences in the BP-1 and BP-3 levels among the studied bat colonies. Mean BP-1 concentration fluctuated from 11.23±13.13 ng/g to 76.71±65.51 ng/g and differed significantly between the colonies. Mean BP-3 concentration fluctuated from 5.03±6.03 ng/g to 9.18±7.65 mg/g, but it did not differ significantly between the colonies. The results show that guano is a suitable matrix for the assessment of wildlife exposure to BPs. This could be particularly advantageous in protected species, where not disturbing and stressing the animals are crucial.

Adverse effect of environmental androgenic compounds Galaxolide and Irgacure 369 on the male reproductive system

Our recent study has found that two environmental chemicals, Galaxolide (HHCB, a raw material for synthesizing musk) and Irgacure 369 (IC-369, a photoinitiator used in packaging) are agonists for the androgen receptor in vitro and in vivo. This study aims to reveal the subchronic reproductive toxicity of these two compounds in mature male rats. The results showed that compared with the control group, HHCB and IC-369 reduced the sperm concentration and motility, increased the sperm deformity, and caused the atrophy of the seminiferous tubules in the testicles. Exposure to HHCB and IC-369 reduced testosterone level, and induced luteinizing hormone, and follicle-stimulating hormone levels in rat serum. Compared with the control group, the levels of oxidative stress markers in the serum and testicular tissue increased. HHCB and IC-369 also inhibited expression of the genes involved in androgen synthesis in testicle. The above results indicated that HHCB and IC-369 could affect the levels of sex hormones, alter gene expression profiles and induce histological damage in reproductive organs, resulting in decreased sperm quality. Therefore, HHCB and IC-369 have endocrine disruptors with prominent reproductive toxicity in males.

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.

Galaxolide and Irgacure 369 are novel environmental androgens

Endocrine disruptors are environmental chemicals that can interfere with the endocrine system. However, research on endocrine disruptors that interfere with androgen's actions is still limited. The purpose of this study is to use in silico computation, i.e., molecular docking to facilitate the identification of environmental androgens. Computational docking was used to study the binding interactions of environmental/industrial compounds with the three dimensional structure of human androgen receptor (AR). Then reporter assay and cell proliferation assay using AR-expressing LNCaP prostate cancer cells were used to determine their in vitro androgenic activity. Animal studies using immature male rats were also carried out to test their in vivo androgenic activity. Two novel environmental androgens were identified. As a photoinitiator, 2-benzyl-2-(dimethylamino)-4'-morpholinobutyrophenone (Irgacure 369, abbreviated as IC-369) is widely used in the packaging and electronics industries. Galaxolide (HHCB) is widely used in the production of perfume, fabric softeners and detergents. We found that both IC-369 and HHCB could activate AR transcriptional activity and promote cell proliferation in AR-sensitive LNCaP cells. Furthermore, IC-369 and HHCB could induce cell proliferation and histological changes of seminal vesicles in immature rats. RNA sequencing and qPCR analysis showed that androgen-related genes in seminal vesicle tissue were up-regulated by IC-369 and HHCB. In conclusion, IC-369 and HHCB are new environmental androgens that bind AR and induce AR transcriptional activity, thereby exerting toxicological effects on the development of male reproductive organs.

Assessment of human exposure to benzophenone-type UV filters: A review

To avoid the harmful effects of UV radiation, benzophenone-type UV filters (BPs) are widely used in personal care products and other synthetic products. Biomonitoring studies have shown the presence of BPs in various human biological samples, raising health concerns. However, there is a paucity of data on the global human exposure to this group of contaminants. In this study, we compiled data on the body burden of BPs along with the possible exposure routes and biotransformation pathways. BPs can easily penetrate the skin barrier and thus, they can be absorbed through the skin. In the human body, BPs can undergo Phase I (mainly demethylation and hydroxylation) and Phase II (mainly glucuronidation and sulfation) biotransformations. From a total of 158 studies, most of the studies are related to urine (concentration up to 92.7 mg L^-1), followed by those reported in blood (up to 0.9 mg L^-1) and milk (up to 0.8 mg L^-1). Among BPs, benzophenone-1 and benzophenone-3 are the most commonly detected congeners. The body burden of BPs is associated with various factors, including the country of residence, lifestyle, income, education level, and ethnicity. The presence of BPs in maternal urine (up to 1.1 mg L^-1), placenta (up to 9.8 ng g^-1), and amniotic fluid (up to 15.7 μg L^-1) suggests potential risks of prenatal exposure. In addition, transplacental transfer of BPs is possible, as demonstrated by their presence in maternal serum and cord serum. The possible association of BPs exposure and health effects was discussed. Future human biomonitoring studies and studies on the potential health effects are warranted. Overall, this review provides a summary of the global human exposure to BPs and can serve as supporting evidence to guide usage in order to protect humans from being exposed to BPs.

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.

Printing ink related chemicals, including synthetic phenolic antioxidants, organophosphite antioxidants, and photoinitiators, in printing paper products and implications for human exposure

Although synthetic antioxidants (AOs) and photoinitiators (PIs) are known to be used in printing inks, there are little data on residual concentrations in printing paper products. In the present study, twenty-five PIs, ten AOs, and six transformation products were analyzed in two types of printing paper products, magazines and paperboard food packaging materials, both of which are unavoidable everyday products in our life. Nine AOs and six transformation products can be detected in food packaging materials with total concentrations (geometric mean, GM) of 1.16 × 10⁴ ng/dm². Twenty-two PIs were detected in food packaging materials with total concentrations (GM) of 1.76 × 10⁴ ng/dm². These chemicals were also detected in magazines, albeit at low concentrations (GM of AOs: 466 ng/dm², GM of PIs: 1.17 × 10³ ng/dm²). Magazine front covers were found to have much higher concentrations of the target compounds than magazine inside pages. Tris(2,4-di-tert-butylphenyl) phosphate (AO168O), 2,6-di-tert-butyl-4-methylphenol (BHT), bisphenol A (BPA), and benzophenone (BP) were among the predominant chemicals in those printing paper products. Preliminary calculations suggest that dermal exposure to AOs (GM: 6.25 ng/day) and PIs (GM: 17.0 ng/day) via contact with printing paper products is a minor exposure pathway compared to food intake/dust ingestion and is exceedingly unlikely to cause adverse health effects.

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.

Structure-Oriented Research on the Antiestrogenic Effect of Organophosphate Esters and the Potential Mechanism

Organophosphate esters (OPEs) can exhibit various toxicities including endocrine disruption activity. Unfortunately, the low-dose endocrine-disrupting effects mediated by estrogen receptors (ERs) are commonly underestimated for OPEs and their metabolites. Here, structure-oriented research was performed to investigate the estrogenic/antiestrogenic effect of 13 OPEs (including three metabolites) and the potential mechanism. All of the OPEs exerted antiestrogenic activities in both E-screen and MVLN assays. OPEs with bulky substituents, such as phenyl rings (triphenyl phosphate (TPP), tricresyl phosphate (TCP), diphenylphosphoryl chloride, and diphenylphosphite) or relatively long alkyl chains (dibutylbutylphosphonate (DBBP)), exerted relatively strong ER antagonism potency at micromolar concentrations. The established quantitative structure-activity relationship indicated that the antiestrogenic activities of the OPEs mainly depended on the volume, leading eigenvalue, and hydrophobicity of the molecule. Molecular docking revealed that the three OPEs with the bulkiest substituents on the phosphate ester group (TPP, TCP, and DBBP) have a similar interaction mode to the classical ER antagonist 4-hydroxytamoxifen. The correlation between the antiestrogenic activity and the corresponding ER binding affinity was statistically significant, strongly suggesting that the OPEs possess the classical antagonism mechanism of interfering with the positioning of helix 12 in the ER.

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.

Cu(I)-Catalyzed Enantioselective Alkynylation of Thiochromones

A highly efficient asymmetric synthesis of chiral thiochromanones is developed via Cu(I)/phosphoramidite catalyzed asymmetric alkynylation of thiochromones under mild reaction conditions. The catalyst system is tolerant of various thiochromone precursors and terminal alkynes. The established asymmetric transformation provides different enatiomeric-enriched thiochromanones with more molecular complexity and enables access to chiral thioflavanones, a subgroup of flavonoid by further functionalization.