Citrate ester substitutes for di-2-ethylhexyl phthalate: In vivo reproductive and in vitro cytotoxicity assessments

Leachates from plastics and bioplastics reduce lifespan, decrease locomotion, and induce neurotoxicity in Caenorhabditis elegans

Plastic pollution continuously accumulates in the environment and poses a global threat as it fragments into microplastics and nanoplastics that can harm ecosystems. To reduce the accumulation of microplastic and nanoplastic pollution, bioplastics made from biodegradable materials are promoted as a more sustainable alternative because it can degrade faster than plastics. However, plastics also leach out chemicals as they degrade and disintegrate, but the potential toxicity of these chemicals leaching out from plastics and especially bioplastics is poorly explored. Here, we determined the composition of leachates from plastics and bioplastics and tested their toxicity in Caenorhabditis elegans. LC-MS analysis of the leachates revealed that bioplastics leached a wider array of chemicals than their counterpart plastics. Toxicity testing in our study showed that the leachates from plastics and bioplastics reduced lifespan, decreased locomotion, and induced neurotoxicity in C. elegans. Leachates from bioplastics reduced C. elegans lifespan more compared to leachates from plastics: by 7%-31% for bioplastics and by 6%-15% for plastics. Leachates from plastics decreased locomotion in C. elegans more compared to leachates from bioplastics: by 8%-34% for plastics and by 11%-24% for bioplastics. No changes were observed in the ability of the C. elegans to respond to mechanical stimuli. The leachates induced neurotoxicity in the following neurons at varying trends: cholinergic neurons by 0%-53% for plastics and by 30%-42% for bioplastics, GABAergic neurons by 3%-29% for plastics and by 10%-23% for bioplastics, and glutamatergic neurons by 3%-11% for plastics and by 15%-29% for bioplastics. Overall, our study demonstrated that chemicals leaching out from plastics and bioplastics can be toxic, suggesting that both plastics and bioplastics pose ecotoxicological and human health risks.

Intergenerational metabolism-disrupting effects of maternal exposure to plasticizer acetyl tributyl citrate (ATBC)

Environmental chemicals and pollutants are increasingly recognized for their potential transgenerational effects. Acetyl tributyl citrate (ATBC), a widely used plasticizer substituting di-(2-ethylhexyl) phthalate (DEHP), was identified as an inducer of lipogenesis in male mice by our previous research. This study aimed to investigate the impact of ATBC exposure on the metabolic homeostasis of female mice and simultaneously evaluate its intergenerational effects. Female C57BL/6J mice were orally exposed to ATBC (0.01 or 1 μg/kg/day) for 10 weeks before mating with unexposed male mice. The resulting F1 female mice were bred with unexposed males to generate F2 offspring. Our results indicated that 10-week ATBC exposure disrupted glucose metabolism homeostasis and the reproductive system in F0 female mice. In F1 female mice, elevated liver lipid levels and mild insulin resistance were observed. In the F2 generation, maternal ATBC exposure resulted in increased weight gain, elevated liver triglycerides, and higher fasting blood glucose levels, primarily in F2 male mice. These findings suggest that maternal ATBC exposure may exert intergenerational disturbing effects on glucose metabolism across generations of mice. Further investigation is needed to evaluate the health risks associated with ATBC exposure.

Effects of two alternative plasticizers on the growth hormone-related endocrine system, neurodevelopment, and oxidative stress of zebrafish larvae

In response to the restriction of phthalate plasticizers, acetyl tributyl citrate (ATBC) and acetyl triethyl citrate (ATEC) have been used in medical devices and food packaging. In the present study, the effects of ATBC and ATEC on the development, behavior, growth hormone (GH)-related endocrine system, neurotransmitters, and oxidative stress of zebrafish embryo or larvae were investigated. After exposure of zebrafish to ATBC and ATEC (0, 0.03, 0.3, 3, 30, and 300 μg/L) for 96 h, developmental toxicity, behavioral changes under light/dark condition, changes in hormones and genes involved in GH/insulin-like growth factors (IGFs) axis, changes in hormone, enzyme, and genes related to neurodevelopment, antioxidant enzymes activities were determined. Larvae exposed to 30 or 300 μg/L ATBC showed significant reductions in body length and moving distance and speed, whereas no significant effects on development and locomotor behavior were observed in larvae exposed to ATEC. The contents of GH and IGF-I were significantly reduced in larvae exposed to 3, 30, and 300 μg/L ATBC. Hormonal changes in fish exposed to ATBC are well supported by regulation of genes related to GH (gh1) and the activity of IGF-I (igf1). In fish exposed to ATBC, reduced acetylcholinesterase activity and down-regulation of genes related to the central nervous system development (ache, gap43, mbpa, and syn21) were observed. ATBC increased the production of reactive oxygen species and the levels of superoxide dismutase, catalase, and glutathione peroxidase. Notably, pre-treatment with the classic antioxidant N-acetylcysteine alleviated ATBC-induced GH-related endocrine disruption and neurotoxicity. Our observations showed that exposure to low levels of ATBC could disturb the regulatory systems of GH/IGFs axis and neurobehavior, ultimately leading to developmental inhibition and hypoactivity, and that increased oxidative stress plays a major role in these toxicities.

Evaluating the risk of phthalate and non-phthalate plasticizers in dust samples from 100 Japanese houses

Phthalates are widely used as plasticizer and associated with various health issues. Recently, non-phthalate plasticizers are replacing phthalates; however, the exposure to these substances and the risk in Japan is unclear. In this study, we assessed the concentrations of phthalates, non-phthalate plasticizers, and phthalate degradation products in house dust and determined their respective exposure risks via oral and dermal routes. Twelve phthalates, seven non-phthalate plasticizers, and two degradation products were determined in the house dust obtained from 100 Japanese homes. The median concentration of di(2-ethylhexyl) phthalate (DEHP), accounting for 85 % of the total concentration of phthalates and non-phthalate plasticizers detected in this study, was 2.1 × 103 μg/g of dust. Apart from DEHP, diisononyl phthalate (DINP) and di(2-ethylhexyl) terephthalate (DEHT) were the most abundant in the house dust, accounting for 6.2 % (median: 1.7 × 102 μg/g of dust) and 6.1 % (median: 1.7 × 102 μg/g of dust) of the total concentrations, respectively. DEHP and DEHT concentrations in house dust were higher in apartment and small houses (floor area: ≤30 m2 or 31-60 m2 for DEHP and 31-60 m2 for DEHT) than in detached and large houses (floor area: ≥121 m2). Conversely, di-n-butyl phthalate (DnBP) concentrations were significantly higher in detached and large houses (floor area: ≥121 m2) than in apartment and small houses (floor area: ≤30 m2). The total hazard quotient (HQ), using the maximum concentration in house dust, revealed that oral and dermal exposure to house dust was 1.3 × 10-6-0.11 for adults (all substances) and 1.6 × 10-5-2.2 × 10-2 for preschool children (except for DnBP and DEHP), suggesting no risk. The HQs for DnBP and DEHP exposure via house dust for preschool children using the maximum values were 0.46 and 1.2, and 6.0 × 10-3 and 0.18 using the median values, indicating that risk of DEHP exposure should be exhaustively determined by considering other exposure routes that were not evaluated in this study, such as diet.

Nonphthalate Plasticizers in House Dust from Multiple Countries: An Increasing Threat to Humans

Along with the restrictions of phthalate esters (PAEs), a variety of nonphthalate plasticizers (NPPs) have been increasingly used for industrial needs. Knowledge remains limited on the environmental occurrences, fate, and human exposure risks of many emerging NPPs. In this study, we investigated a suite of 45 NPPs along with the major PAEs in house dust from five regions in the Asia-Pacific region and the United States. The findings clearly demonstrated ubiquitous occurrences of many NPPs in the home environment, particularly acetyl tributyl citrate (ATBC), tricapryl trimellitate (TCTM), trioctyl trimellitate (TOTM), glycerol monooleate (GMO), methyl oleate (MO), and diisobutyl adipate (DiBA). The median total concentrations of NPPs ranged from 17.8 to 252 μg/g in the study regions, while the mean ratios of ΣNPPs to ΣPAEs ranged from 0.19 (Hanoi) to 0.72 (Adelaide). Spatial differences were observed not only for the chemical abundances but also for the composition profiles and the hazard quotient (HQ) prioritization of individual chemicals. Although the current exposure may unlikely cause significant health risks according to the HQ estimation, potential exposure risks cannot be overlooked, due to the lack of appropriate toxic threshold data, the existence of additional exposure pathways, and possible cocktail effects from coexisting NPPs and PAEs.

Medical devices as a source of phthalate exposure: a review of current knowledge and alternative solutions

Phthalates are a group of phthalic acid esters used as plasticisers in a large number of products to improve their flexibility, softness, and extensibility. Their wide use in medical devices, however, raises a lot of concern, as they can enter the organism and have toxic effects on human liver, thyroid, kidneys, lungs, reproductive, endocrine, nervous, and respiratory system and are associated with asthma, obesity, autism, and diabetes. The aim of this review is to summarise current knowledge about phthalate migration from medical devices during different medical procedures and possible impact on patient health. It also looks at alternative plasticisers with supposedly lower migration rates and safer profile. Not enough is known about which and how many phthalates make part of medical devices or about the health impacts of alternative plasticisers or their migration rates.

Coupled Dynamic Material Flow, Multimedia Environmental Model, and Ecological Risk Analysis for Chemical Management: A Di(2-ethylhexhyl) Phthalate Case in China

Di(2-ethylhexhyl) phthalate (DEHP) is a widely used plasticizer that has adverse effects on ecosystems and human health. However, data about its stocks, flows, emission rates, as well as ecological risks are generally unknown in China, one of the world's largest producers of chemicals including DEHP, limiting sound management of chemicals. Herein, dynamic material flow analysis, coupled with a multimedia environmental model and ecological risk analysis, was performed to fill the data gap about DEHP in China mainland from 1956 to 2020. Results indicate that the in-use stocks of DEHP increased from 6.54 × 10⁶ kg in 1956 to 8.40 × 10⁹ kg in 2020. With growth in the emission rates, DEHP concentrations in air, soil, water, and sediment kept increasing from 1956 to 2010, which declined after 2010 and regrew after 2015. Sediment was a main sink of DEHP with the highest ecological risk quotient of >10 after 1999, necessitating measures for controlling the risk, for example, technology innovation to reduce DEHP emission rates, and substitution of DEHP with low-toxic alternatives. The coupled models that connect socio-economic data with ecological risk output may provide a systematic methodology for verification of the data necessary for risk control of chemicals.

Di-n-butyl phthalate disrupts neuron maturation in primary rat embryo neurons and male C57BL/6 mice

Di-n-butyl phthalate (DBP) is commonly used as a plasticizer and its usage continues to increase in conjunction with plastic consumption. DBP is readily released into air, drinking water, and soil, and unfortunately, is a potent endocrine disrupter that impairs central nervous system functions. Previously DBP was found to (1) arrest the cell cycle of C17.2 neural progenitor cells (NPCs) at the G1 phase, (2) reduce numbers of newly generated neural stem cells in the mouse hippocampus, and (3) adversely affect learning and memory. Other investigators also noted DBP-mediated neurotoxic effects, but as yet, no study has addressed the adverse effects of DBP on neuronal differentiation. Data demonstrated that at 200 μM DBP induced apoptosis in rat embryo primary neurons by increasing reactive oxygen species levels and inducing mitochondrial dysfunction. However, no significant effect was detected on neurons at concentrations of ≤100 μM. In contrast, doublecortin/microtubule associated protein-2 (DCX/MAP2) immunocytochemistry showed that DBP at 100 μM delayed neuronal maturation by increasing protein levels of DCX (an immature neuronal marker), without markedly affecting cell viability. Further in vivo studies confirmed that DCX⁺ cell numbers were significantly elevated in the hippocampus of DBP-treated mice, indicating that DBP delayed neuronal maturation, which is known to be associated with impaired memory retention. Data demonstrated that DBP might disrupt neuronal maturation, which is correlated with reduced neurocognitive functions.

Role of mitochondria-endoplasmic reticulum coupling in lycopene preventing DEHP-induced hepatotoxicity

Di (2-ethylhexyl) phthalate (DEHP) is a hazardous compound used as a plasticizer in plastic products. As a natural carotenoid, lycopene (LYC) is considered an effective protective agent against various types of organ damage. The present study aimed to investigate the role of mitochondria-endoplasmic reticulum (ER) coupling in LYC preventing DEHP-induced hepatotoxicity. The mice were treated with LYC (5 mg kg^-1) and/or DEHP (500 or 1000 mg kg^-1). In the present study, LYC prevented DEHP-induced histopathological changes including fibrosis and glycogen storage in the liver. Additionally, LYC alleviated DEHP-induced ultrastructural injury of mitochondria and ER. LYC had the underlying preventability against DEHP-induced mitochondrial dynamics imbalance including an increase in fission and a decrease in fusion. Furthermore, DEHP induced mitochondria-associated endoplasmic reticulum membrane (MAM) disorder-induced ER stress through the ER unfolded protein response (UPR^ER), but LYC alleviated these alterations. Therefore, LYC prevented DEHP-induced hepatic mitochondrial dynamics and MAM disorder, leading to ER stress. The present study provides novel evidence of mitochondria-ER coupling as a target for LYC that prevents DEHP-induced hepatotoxicity.

Testicular dysgenesis syndrome and phthalate exposure: A review of literature

Endocrine disruptors are chemicals that interfere with the body's endocrine system and cause adverse effects in biological systems. Phthalates are a group of man-made chemicals which are mainly used as plasticizers and classified as endocrine disruptors. They are also used in cosmetic and personal care products as color or smell fixators. Moreover, phthalates are present in inks, adhesives, sealants, automobile parts, tools, toys, carpets, medical tubing and blood storage bags, and food packages. Pathological condition known as "testicular dysgenesis syndrome" (TDS) or "phthalate syndrome" is usually linked to phthalate exposure and is coined to describe the rise in alterations in reproductive health in men, such as reduced semen quality (decrease in sperm counts, sperm motility and increase in abnormal sperms), hypospadias, cryptorchidism, reduced anogenital distance and early-life testicular cancer. Phthalates are suggested to cause direct effect on gonadal and non-gonadal tissues, impair the differentiation and morphogenesis of seminiferous tubules and accessory sex organs and testicular cells (both Sertoli and Leydig cells), alter estradiol and/or testosterone levels, decrease insulin-like 3 (INSL3) peptide production, impair spermatogenesis and lead to epigenetic alterations, all of which may lead to TDS. This review will mainly focus on phthalates as causes of TDS and their mechanisms of action.

Transplantation of encapsulated human Leydig-like cells: A novel option for the treatment of testosterone deficiency

Previous studies have demonstrated that the transplantation of alginate-poly-ʟ-lysine-alginate (APA)-encapsulated rat Leydig cells (LCs) provides a promising approach for treating testosterone deficiency (TD). Nevertheless, LCs have a limited capacity to proliferate, limiting the efficacy of LC transplantation therapy. Here, we established an efficient differentiation system to obtain functional Leydig-like cells (LLCs) from human stem Leydig cells (hSLCs). Then we injected APA-encapsulated LLCs into the abdominal cavities of castrated mice without an immunosuppressor. The APA-encapsulated cells survived and partially restored testosterone production for 90 days in vivo. More importantly, the transplantation of encapsulated LLCs ameliorated the symptoms of TD, such as fat accumulation, muscle atrophy and adipocyte accumulation in bone marrow. Overall, these results suggest that the transplantation of encapsulated LLCs is a promising new method for testosterone supplementation with potential clinical applications in TD.