Octamethylcyclotetrasiloxane exhibits estrogenic activity in mice via ERα

Assessing the impact of mining on cyclic and linear methylsiloxane distribution in Tibetan soils: Source contribution and transport pattern

The pervasive presence of methylsiloxanes (MSs), comprising linear and cyclic congeners, in the environment poses significant ecological risks, yet the understanding of their transport mechanisms and deposition patterns remains limited. This study analyzed the concentrations of 12 linear-MSs (L3-L14) and 7 cyclic-MSs (D3-D9) in 29 surface soil samples collected across varying altitudes (3726 to 4863 m) near the Jiama mining sector in Tibet, aiming to investigate the distribution and transport dynamics of MSs from the emission source. The distribution of total MS concentration (ranging from 50.1 to 593 ng/g) showed a remarkable correlation with proximity to the mining site, suggesting the emergent source of mining activities for the MSs in the remote environment of the Tibetan Plateau. Employing the innovative model of robust absolute principal component scores-robust geographically weighted regression (RAPCS-RGWR), the analysis predicted that the mining operations contributing 57.1 % of the total soil MSs, would significantly surpass contributions from traffic emissions (14.7 %), residential activities (13.2 %), and the environmental factor of total organic matter content (14.9 %). The Boltzmann equation effectively modeled the distribution pattern of soil MSs, highlighting atmospheric transport and gravitational settling as key distribution mechanisms. However, linear-MSs exhibited longer transport distances than cyclic-MSs and were more profoundly affected by prevailing wind directions, suggesting their differential environmental behaviors and risks. Our study underscored that the mining sector possibly emerged as a significant source of Tibetan MSs, and provided insights into the transport and fate of MSs in remote, high-altitude environments. The findings emphasize the need for targeted pollution control strategies to mitigate the environmental footprint of mining activities in Tibet and similar regions.

Cyclic volatile methyl siloxanes (D4, D5, and D6) as the emerging pollutants in environment: environmental distribution, fate, and toxicological assessments

Cyclic volatile methyl siloxanes (cVMS) have now become a subject of environmental contamination and risk assessment due to their widespread use and occurrence in different environmental matrices. Due to their exceptional physio-chemical properties, these compounds are diversely used for formulations of consumer products and others implying their continuous and significant release to environmental compartments. This has captured the major attention of the concerned communities on the grounds of potential health hazards to human and biota. The present study aims at comprehensively reviewing its occurrence in air, water, soil, sediments, sludge, dusts, biogas, biosolids, and biota and their environmental behavior as well. Concentrations of cVMS in indoor air and biosolids were higher; however, no significant concentrations were observed in water, soil, and sediments except for wastewaters. No threat to the aquatic organisms has been identified as their concentrations do not exceed the NOEC (maximum no observed effect concentration) thresholds. Mammalian (rodents) toxicity hazards were not very evident except for the occurrence of uterine tumors in very rare cases under long-term chronic and repeated dose exposures in laboratory conditions. Human relevancy to rodents were also not strongly enough established. Therefore, more careful examinations are required to develop stringent weight of evidences in scientific domain and ease the policy making with respect to their production and use so as to combat any environmental consequences.

Emerging organic contaminants in drinking water systems: Human intake, emerging health risks, and future research directions

Few earlier reviews on emerging organic contaminants (EOCs) in drinking water systems (DWS) focused on their detection, behaviour, removal and fate. Reviews on multiple exposure pathways, human intake estimates, and health risks including toxicokinetics, and toxicodynamics of EOCs in DWS are scarce. This review presents recent advances in human intake and health risks of EOCs in DWS. First, an overview of the evidence showing that DWS harbours a wide range of EOCs is presented. Multiple human exposure to EOCs occurs via ingestion of drinking water and beverages, inhalation and dermal pathways are discussed. A potential novel exposure may occur via the intravenous route in dialysis fluids. Analysis of global data on pharmaceutical pollution in rivers showed that the cumulative concentrations (μg L-1) of pharmaceuticals (mean ± standard error of the mean) were statistically more than two times significantly higher (p = 0.011) in South America (11.68 ± 5.29), Asia (9.97 ± 3.33), Africa (9.48 ± 2.81) and East Europe (8.09 ± 4.35) than in high-income regions (2.58 ± 0.48). Maximum cumulative concentrations of pharmaceuticals (μg L-1) decreased in the order; Asia (70.7) had the highest value followed by South America (68.8), Africa (51.3), East Europe (32.0) and high-income regions (17.1) had the least concentration. The corresponding human intake via ingestion of untreated river water was also significantly higher in low- and middle-income regions than in their high-income counterparts. For each region, the daily intake of pharmaceuticals was highest in infants, followed by children and then adults. A critique of the human health hazards, including toxicokinetics and toxicodynamics of EOCs is presented. Emerging health hazards of EOCs in DWS include; (1) long-term latent and intergenerational effects, (2) the interactive health effects of EOC mixtures, (3) the challenges of multifinality and equifinality, and (4) the Developmental Origins of Health and Disease hypothesis. Finally, research needs on human health hazards of EOCs in DWS are presented.

Assessment of the internal and external exposure risks to methylsiloxanes in communities near a petroleum refinery

Methylsiloxanes (MSs) are widely used in industrial production and have attracted much attention due to their potential health risks to humans. MSs are present in emissions from petroleum refining, and it is therefore important to assess the health risks to residents living near refineries. In this study, we evaluated the pollution characteristics and human exposure risks of three cyclic MS (CMS) oligomers (D4-D6) in areas upwind and downwind of a petroleum refinery. The concentrations of total CMSs were 4-33 times higher in the downwind than upwind areas. At the same sampling site, the concentrations of CMSs were higher indoors than outdoors. The maximum concentration of CMSs was found in the indoor environment 200 m downwind of the petroleum refinery (75 μg/m3 in air and 2.3 μg/g in dust). The concentrations and detection rates of CMSs in plasma samples were higher in the downwind than upwind residents. Although residents living downwind of the petroleum refinery were a non-occupationally exposed population, they should be considered a highly CMS-exposed population because of their extremely high internal exposure doses. Inhalation exposure was the main source of CMSs in the plasma of these residents. When different exposure pathways were investigated, inhalation exposure was the major contributor to the average daily dose in residents of locations near the petroleum refinery, whereas the dermal absorption of personal care products was the major contributor at other sites. Although the overall risks of exposure to total CMSs were below the chronic reference dose for all exposure pathways, the combined joint toxic effects of various CMSs remain unclear. Further studies are therefore required to determine the exposure risks and subsequent health effects of CMSs for the residents of these areas.

The development and application of a novel hazard scoring tool for assessing impacts of cosmetic ingredients on aquatic ecosystems: A case study of rinse-off cosmetics

The cosmetic industry has been committed to promoting less hazardous products to reduce the environmental impacts of cosmetic ingredients. This requires identifying safer cosmetic ingredients for developing cosmetic formulations that are less harmful to the environment. However, one of the challenges in developing eco-friendly cosmetics relies on integrating all environmental hazard (EH) information of cosmetic ingredients to select the most eco-friendly ones (i.e., ingredients least harmful to the aquatic environment). Thus, we developed a hazard scoring tool (IARA matrix), which integrates data on biodegradation, bioaccumulation, and acute aquatic toxicity, providing a hazard index to classify cosmetic ingredients (raw materials) into categories of EH (low, moderate, high, or very high). The classification of the IARA was based on parameters established by Cradle to Cradle (C2C), the US Environmental Protection Agency (USEPA), and European Regulation 1272/2008, considering the most conservative values of each source. The Leopold matrix was employed as a model for the tool, using a numerical scale from 0 to 6 (lowest to highest EH). According to the IARA, we have successfully demonstrated that ultraviolet (UV) filter ingredients have the highest EH out of 41 cosmetic ingredients commonly used for rinse-off products. In addition to UV filters, triclosan (bactericide) and dimethicone (emollient) presented the second-highest EH for aquatic ecosystems, and humectants presented the lowest hazard index. By applying the IARA in the case study of rinse-off products, we have estimated that the aquatic hazard of cosmetic products can be reduced 46% by identifying less hazardous ingredients and combining them into a cosmetic formulation. In summary, the IARA tool allows the estimation of the EH of cosmetic ingredients, provides safer products, and helps achieve sustainability for cosmetic products. Integr Environ Assess Manag 2023;19:1619-1635. © 2023 SETAC.

Cytotoxicity, endocrine disrupting activity, and chemical analysis of 42 food contact silicone rubber products

After migration in 95 % ethanol (food simulant) at 70 °C for 2 h (accelerated conditions), the cytotoxicity and endocrine-disruption activity of 42 food contact silicone products (FCSPs) obtained from the Chinese market were studied. Of 31 kitchenwares, 96 % showed mild or above cytotoxicity (relative growth rate < 80 %) using the HeLa neutral red uptake test; and 84 % showed estrogenic (64 %), anti-estrogenic (19 %), androgenic (42 %), and anti-androgenic (39 %) activities by the Dual-luciferase reporter gene assay. The mold sample induced late phase HeLa apoptosis as detected by Annexin V-FITC/PI double staining flow cytometry, in addition, the migration of mold sample has a higher risk of endocrine disruption at high temperature usage. Encouragingly, 11 bottle nipples had neither cytotoxic nor hormonal activity. Utilizing multiple mass spectrometry techniques, non-intentionally added substances (NIASs) in 31 kitchenwares were analyzed, and the migration levels of 26 organic compounds and 21 metals were quantified, furthermore, the safe risk of single migrant was evaluated through their special migration limit (SML) or threshold of toxicological concern (TTC). Using "nchoosek" statement and Spearman's correlation analysis in MATLAB, the migration of 38 compounds or combinations including metals, plasticizers, methylsiloxanes, and lubricants, had strong correlation with cytotoxicity or hormonal activity. The coexistence of various chemical substances in migrants leads to complex biological toxicity of FCSPs, so it is very important to detect the toxicity of the final products. The combination of bioassays and chemical analyses are valuable tools to facilitate the identification and analyses of FCSPs and migrants that have potential safety risks.

Occurrence and fate of chlorinated methylsiloxanes in surrounding aqueous systems of Shengli oilfield, China

Mono-chlorinated products of cyclic volatile methylsiloxanes (cVMS), i.e., Monochlormet-hylheptamethylcyclotetrasiloxane [D3D(CH₂Cl)], monochlormethylnonamethylcyclopenta-siloxane [D4D(CH₂Cl)], and monochlormethylundemethylcyclohexasiloxane [D5D(CH₂Cl)], were detected in water [<LOQ (Limit of quantitation) -86.3 ng/L, df (detection frequency) = 23%-38%, n=112] and sediment samples [<LOQ-504 ng/g dw (dry weight), df = 33%-38%, n=112] from 16 lakes located in Shengli oilfield of China, and had apparent increasing trends (31%-34% per annum) in sediments during Year 2014-2020. Simulated experiments showed that chloro-cVMS in sediment-water system had approximately 1.7-2.0 times slower elimination rates than parent cVMS. More specifically, compared with those of parent cVMS, volatilization (86-2558 days) and hydrolysis (135-549 days) half-lives of chloro-cVMS were respectively 1.3-2.0 and 1.8-2.1 times longer. In two species of freshwater mussels (n=1050) collected from six lakes, concentrations of chloro-cVMS ranged from 9.8-998 ng/g dw in Anodonta woodiana and 8.4-970 ng/g dw in Corbicula fluminea. Compared with parent cVMS, chloro-cVMS had 1.1-1.5 times larger biota-sediment accumulation factors (2.1-3.0) and 1.1-1.7 times longer half-lives (13-42 days). Their stronger persistence in sediment and bioaccumulation in freshwater mussels suggested that environmental emission, distribution and risks of chloro-cVMS deserve further attention.

Occurrence of methylsiloxanes in indoor store dust in China and potential human exposure

Methylsiloxanes are synthetic molecules with versatile and extensive applications. Because of their volatile properties, they are easily released from manufactured products and contaminate indoor environments, causing high human exposure. However, available information on their presence in specific microenvironments, and on the related potential risks for human health, is limited. We conducted a survey of sixteen methylsiloxanes species, including three cyclic (D₄-D₆) and thirteen linear (L₄-L₁₆) chemicals, in indoor dust samples from twenty-eight stores representative of six store categories in Beijing, China. Total methylsiloxane concentrations in store dust were 176-54,825 ng/g, depending on the store, with a median of 2196 ng/g. Linear chemicals represented a median proportion of 90.8% of total methylsiloxanes. The measured methylsiloxane concentrations in this study were marginally higher than those reported previously for standard living and working environments. The highest linear and total methylsiloxane concentrations were measured in electronic stores, while the highest cyclic methylsiloxane concentrations were measured in department stores. The presence of methylsiloxanes in the store dust samples was attributed mainly to their release from chemical additives in marketed products. Estimated median total exposure doses under normal and worst-case exposure scenarios were 0.237 and 0.888 ng/kg bw/d, respectively. Further investigation is needed to characterize methylsiloxane distribution in other microenvironments and to evaluate the associated health risks.

Hormone receptor activities of complex mixtures of known and suspect chemicals in personal silicone wristband samplers worn in office buildings

Humans are exposed to increasingly complex mixtures of hormone-disrupting chemicals from a variety of sources, yet, traditional research methods only evaluate a small number of chemicals at a time. We aimed to advance novel methods to investigate exposures to complex chemical mixtures. Silicone wristbands were worn by 243 office workers in the USA, UK, China, and India during four work shifts. We analyzed extracts of the wristbands for: 1) 99 known (targeted) chemicals; 2) 1000+ unknown chemical features, tentatively identified through suspect screening; and 3) total hormonal activities towards estrogen (ER), androgen (AR), and thyroid hormone (TR) receptors in human cell assays. We evaluated associations of chemicals with hormonal activities using Bayesian kernel machine regression models, separately for targeted versus suspect chemicals (with detection ≥50%). Every wristband exhibited hormonal activity towards at least one receptor: 99% antagonized TR, 96% antagonized AR, and 58% agonized ER. Compared to men, women were exposed to mixtures that were more estrogenic (180% higher, adjusted for country, age, and skin oil abundance in wristband), anti-androgenic (110% higher), and complex (median 836 detected chemical features versus 780). Adjusted models showed strong associations of jointly increasing chemical concentrations with higher hormonal activities. Several targeted and suspect chemicals were important co-drivers of overall mixture effects, including chemicals used as plasticizers, fragrance, sunscreen, pesticides, and from other or unknown sources. This study highlights the role of personal care products and building microenvironments in hormone-disrupting exposures, and the substantial contribution of chemicals not often identifiable or well-understood to those exposures.

Evaluation of Senna tora (L.) Roxb. leaves as source of bioactive molecules with antioxidant, anti-inflammatory and antibacterial potential

Senna tora (L.) Roxb. is an ethno-medicinal herb used by rural and tribal people of the Satpura region of Madhya Pradesh in India and the Phatthalung Province of Thailand for treating rheumatism, bronchitis, ringworm, itches, leprosy, dyspepsia, liver disorders and heart disorders. It is also used in Chinese and Ayurvedic medicine. This study was conducted to investigate the potential of Senna tora (L.) Roxb. as a source of drug candidates against oxidants, inflammation, and bacterial infection. Preliminary phytochemical screening (PPS) and GC-MS were performed to identify the phytochemicals in the ethyl acetate extract of Senna tora (L.) Roxb. leaves (EAESTL). The in vitro antioxidant activity was assessed by 2,2-diphenyl-1-picrylhydrazyl (DPPH)- and H₂O₂-scavenging tests; the in vitro anti-inflammatory activity was determined by bovine serum albumin (BSA) denaturation and red blood cell (RBC) hemolysis inhibition; and the antibacterial activity was evaluated by agar-well diffusion methods. Cytotoxicity was estimated by Artemia salina larvae lethality, while acute toxicity was evaluated by oral delivery of the extract to mice. In silico antioxidant, anti-inflammatory, and antibacterial activities were predicted by the Prediction of Activity Spectra for Substances (PASS) program. The pharmacokinetics related to ADME and toxicity tests were determined by the admetSAR2 and ADMETlab2 web servers, and drug-able properties were assessed by the SwissADME server. GC-MS detected fifty-nine phytochemicals that support the types of compounds (phenols, flavonoids, tannins, terpenoids, saponins, steroids, alkaloids, glycosides and reducing sugar) identified by phytochemical screening. EAESTL exhibited dose-dependent antioxidant, anti-inflammatory, and antibacterial activities without any adverse effects or fluctuations in body weight. The PASS program predicted that the identified phytochemicals have antioxidant, anti-inflammatory and antibacterial activities. Among 51 phytochemicals, 16 showed good ADME, and 8 fulfilled drug-able properties without toxicity. Altogether, four phytochemicals, viz., benzyl alcohol, 3-(hydroxy-phenyl-methyl)-2,3-dimethyl-octan-4-one, phenylethyl alcohol and 2,6,6-trimethylbicyclo [3.1.1] heptane-3-ol, showed good pharmacokinetics and drug-able properties without toxicity, along with antioxidant, anti-inflammatory, and antibacterial activities. The obtained results suggest that Senna tora (L.) Roxb. leaves contain bioactive phytochemicals that have the potential to fight against oxidants, inflammation, and bacterial infection as potential drug candidates.

Plant uptake potential and soil persistence of volatile methylsiloxanes in sewage sludge amended soils

Volatile methylsiloxanes (VMSs) are organosilicon compounds, ubiquitous in modern life. Due to their high use in consumer products, large amounts of these compounds are released into sewer systems, reaching wastewater treatment plants (WWTPs). Its frequent detection in sewage sludge can be of concern when considering its land application, not only due to potential negative impacts on the environment, but also on human health. In this work, the effects of sewage sludge application on plant development and crop productivity were studied, as well as VMSs persistence in the soil and their plant uptake. This study focused on 7 VMSs (D3, D4, D5, D6, L3, L4 and L5) and consisted of a 12-week greenhouse pot experiment, where sewage sludge-amended soils were used to cultivate Pisum sativum (peas). Sewage sludge application to soils had no negative effects on plant development and was tied to crop productivity improvements. Most of the VMSs were still present in soils at the end of the experiment and plant uptake and translocation of the 4 cyclic VMSs (D3, D4, D5, D6) occurred. VMSs were detected in plant tissues up to 161 ± 27 ng g^-1 dw (samples of stems, leaves and tendrils), but did not exceed 50 ± 19 ng g^-1 dw in peas, which did not translate into a human exposure risk due to ingestion, according to an intake risk assessment. However, soil risk assessments showed that for L5 the hazardous ratios were higher than the threshold value of 1. This means a potential environmental risk despite the low levels of this compound in soils (up to 7.3 ± 0.7 ng g^-1 dw). Considering these results, sewage sludge monitoring plans should be defined for VMSs, namely when its final destination is land application, thus allowing a safer management of this residue, taking advantage of its valorization potential.

Developmental effects of siloxane exposure in zebrafish: a comparison study using laboratory-mixed and environmental water samples

Siloxanes are used in personal care, biomedical, and industrial products. Their worldwide use and persistence in the environment cause consistent exposure for both humans and aquatic animals. Two siloxane congeners, decamethylcyclopentasiloxane (D5; CAS 541-02-6) and octamethylcyclotetrasiloxane (D4; CAS 556-67-2), are among the most prevalent, with measurable levels in air, sediment, water, and biological samples. However, few studies have examined the impact of developmental (embryo/larva) exposure. To address this gap, we performed parallel experiments using wildtype zebrafish (Danio rerio). One set of experiments used laboratory-mixed individual solutions containing either D4, D5, or 2,4,6,8-tetramethylcyclotetrasiloxane (D₄ ^H ; CAS 2370-88-9); the other used environmental water samples containing a mixture of siloxanes, including D4 and D5. These samples were collected from Bladensburg Waterfront Park (BWP) a site along the Anacostia River, Washington, DC. In both experiments, zebrafish (24-48 hours postfertilization, hpf) were exposed until 7 or 14 days (d)pf. Chronic exposure to D4, D5, or BWP water until 7 dpf caused stress-like behaviors and reduced swim velocities; anatomical differences were noted only in BWP-exposed larvae. At 14 dpf, BWP-treated larvae still showed slower swimming velocities and increased immobility; anatomical differences were no longer evident and thigmotactic behavior was reduced. D4 and D5-exposed larvae did not survive after 10 dpf. Larvae exposed to D₄ ^H showed no decreases in behavior or growth at either age. These results suggest early developmental sensitivity to siloxane exposure and point to the need to consider embryonic/larval endpoints when assessing aquatic contaminants.

A large contribution of methylsiloxanes to particulate matter from ship emissions

The chemical and stable carbon isotopic composition of the organic aerosol particles (OA) emitted by a shuttle passenger ship between mainland Naples and island Capri in Italy were investigated. Various methylsiloxanes and derivatives were found in particulate ship emissions for the first time, as identified in the mass spectra of a thermal desorption - proton transfer reaction - mass spectrometer (TD-PTR-MS) based on the natural abundance of silicon isotopes. Large contributions of methylsiloxanes to OA (up to 59.3%) were found under inefficient combustion conditions, and considerably lower methylsiloxane emissions were observed under cruise conditions (1.2% of OA). Furthermore, the stable carbon isotopic composition can provide a fingerprint for methylsiloxanes, as they have low δ¹³C values in the range of -44.91‰ ± 4.29‰. The occurrence of methylsiloxanes was therefore further supported by low δ¹³C values of particulate organic carbon (OC), ranging from -34.7‰ to -39.4‰, when carbon fractions of methylsiloxanes in OC were high. The δ¹³C values of OC increased up to around -26.7‰ under cruise conditions, when carbon fractions of methylsiloxanes in OC were low. Overall, the δ¹³C value of OC decreased linearly with increasing carbon fraction of methylsiloxanes in OC, and the slope is consistent with a mixture of methylsiloxanes and fuel combustion products. The methylsiloxanes in ship emissions may come from engine lubricants.

Assessing Modes of Action, Measures of Tissue Dose and Human Relevance of Rodent Toxicity Endpoints with Octamethylcyclotetrasiloxane (D4)

Octamethylcyclotetrasiloxane (D4), a highly lipophilic, volatile compound with low water solubility, is metabolized to lower molecular weight, linear silanols. Toxicity has been documented in several tissues in animals following mixed vapor/aerosol exposures by inhalation at near saturating vapor concentrations or with gavage dosing in vegetable oil vehicles. These results, together with more mechanism-based studies and detailed pharmacokinetic information, were used to assess likely modes of action (MOAs) and the tissue dose measures of D4 and metabolites that would serve as key events leading to these biological responses. This MOA analysis indicates that pulmonary effects arise from direct epithelial contact with mixed vapor/aerosol atmospheres of D4; liver hypertrophy and hepatocyte proliferation arise from adaptive, rodent-specific actions of D4 with nuclear receptor signaling pathways; and, nephropathy results from silanol metabolites binding with alpha-2μ globulin (a rat specific protein). At this time, the MOAs of other liver effects - pigment accumulation and bile duct hyperplasia (BDH) preferentially observed in Sprague-Dawley (SD) rats- are not known. Hypothalamic actions of D4 delaying the rat mid-cycle gonadotrophin releasing hormone (GnRH) surge that result in reproductive effects and subsequent vaginal/uterine/ovarian tissue responses, including small increases in incidence of benign endometrial adenomas, are associated with prolongation of endogenous estrogen exposures due to delays in ovulation. Human reproduction is not controlled by a mid-cycle GnRH surge. Since the rodent-specific reproductive and the vaginal/uterine/ovarian tissue responses are not relevant for risk assessments in human populations, D4 should neither be classified as a CMR (i.e., carcinogenic, mutagenic, or toxic for reproduction) substance nor be regarded as an endocrine disruptor. Bile duct hyperplasia (BDH) and pigment accumulation in liver seen in SD rats are endpoints that could serve to define a Benchmark Dose or No-Observed-Effect-Level (NOEL) for D4.

A mechanistic evaluation of the potential for octamethylcyclotetrasiloxane to produce effects via endocrine modes of action

This review is a hypothesis driven, mechanistic evaluation of the potential for octamethylcyclotetrasiloxane (D4) to produce any effects via endocrine modes of action. D4 is a volatile, lipophilic liquid used in the production of high molecular weight dimethylsiloxane polymers. These are used in a variety of industrial, medical, cleaning, and personal care products, and they may contain low levels of residual D4. Low concentrations of D4 are found in the environment and there is potential for low level human exposure. All of the measured environmental and workplace levels of D4 fall below no observed effect levels (NOEL). Most of the effects of high dose D4 involve the female reproductive system. In the mature intact female rat following chronic high dose exposure, D4 may cause inhibition of mating and ovulation, decreased live litter sizes, small increases in the estrogen to progesterone ratio primarily through decreases in progesterone, and increases in uterine hyperplasia. When endogenous estrogens are very low, high dose D4 causes increases in some uterine parameters. To assess whether these high dose effects can be attributed to an endocrine mode of action, endpoints are ranked for relevance and strength, consistent with published concepts. When sufficient information is available the level of activity of D4 for producing the observed effect is compared with that of potent endocrines. The conclusions reached are that all of the effects of D4 fall well short of any established criteria for D4 to be capable of producing any adverse effect via an endocrine mode of action.

Prenatal Octamethylcyclotetrasiloxane Exposure Impaired Proliferation of Neuronal Progenitor, Leading to Motor, Cognition, Social and Behavioral Functions

Cyclic siloxane octamethylcyclotetrasiloxane (D4) has raised concerns as an endocrine-disrupting chemical (EDC). D4 is widely used in detergent products, cosmetics, and personal care products. Recently, robust toxicological data for D4 has been reported, but the adverse effects of D4 on brain development are unknown. Here, pregnant mice on gestational day 9.5 were treated daily with D4 to postnatal day 28, and the offspring mice were studied. The prenatal D4-treated mice exhibited cognitive dysfunction, limited memory, and motor learning defect. Moreover, prenatal D4 exposure reduced the proliferation of neuronal progenitors in the offspring mouse brain. Next, the mechanisms through which D4 regulated the cell cycle were investigated. Aberrant gene expression, such as cyclin-dependent kinases CDK6 and cyclin-dependent kinase inhibitor p27, were found in the prenatal D4-treated mice. Furthermore, the estrogen receptors ERa and ERb were increased in the brain of prenatal D4-treated mice. Overall, these findings suggest that D4 exerts estrogen activity that affects the cell cycle progression of neuronal progenitor cells during neurodevelopment, which may be associated with cognitive deficits in offspring.

Occurrence of methylsiloxanes in sediments from a subtropical river-lake system in eastern China and its implication for ecological risks

Distribution of methylsiloxanes in environment is still far from being well studied. Little is known about the concentrations and associated risks of these chemicals in river-lake systems. This study investigated the occurrence of twelve methylsiloxanes (D₄-D₆, L₅-L₁₃) in the sediments from Lake Chaohu and its inflowing rivers, China, and found the total concentrations (ng/g dry weight) were in the range of 47.1-496 and 239-3593, respectively. Linear congeners were dominant, representing a median of 62.8% and 58.7% of the total concentrations found in the lake and its inflowing rivers, respectively. In general, the concentrations of sediment methylsiloxanes in the investigated river-lake system were low to moderate, compared with the results reported previously in other waters. Source assessment indicated that the emissions from industrial activities and the use of silicone-containing products were the main contributors of sediment methylsiloxanes in the investigated waters. D₄ and D₅ in 18.5% and 11.1% of river sediment samples might pose ecological risks to fish. The risks from the linear congeners in sediments in the area were not estimated due to no related benchmarks available. More studies are needed to investigate the occurrence of these chemicals and associated risks in aquatic environment.

Methylsiloxanes in street dust from Hefei, China: Distribution, sources, and human exposure

Methylsiloxanes are widely found in the environment and have been of increasing concern because of their strong resistance to degradation and potential toxicity to organisms. However, little is known about the distributions of these chemicals in street dust and the associated human health risks. This study investigated three cyclic (D₄-D₆) and nine linear methylsiloxanes (L₅-L₁₃) in street dust from Hefei, China and found total concentrations in the range of 183-1030 (median, 527) ng/g dry weight. The linear congeners were dominant and represented a median of 85.3% of the total methylsiloxanes. D₅ contributed 90.0% of the total concentrations of cyclic methylsiloxanes. In this study, higher concentrations of dust methylsiloxanes were found in the industrial area relative to the other functional areas. A source assessment indicated that the linear and cyclic methylsiloxanes in the street dust were mainly from the industrial and traffic activities, respectively, in addition to important sources of the use of siloxanes-containing products. The estimated median daily intakes of total methylsiloxanes through street dust were 0.037 and 0.476 ng/kg-bw/d for adults and children, respectively, under high-exposure scenarios. More research is needed to characterize the occurrence of methylsiloxane in various exposure sources and the associated adverse effects on human health.

Assessment of internal exposure to methylsiloxanes in children and associated non-dietary exposure risk

Methylsiloxanes (MSs) are a significant source of indoor environmental pollution due to their high production level and widespread application, and pose a potential health risk. Given the special vulnerability of children to environmental contaminants, assessment of indoor MSs exposure in children is quite essential. In this study, we assessed internal exposure doses and external exposure levels of MSs in children from industrial and residential areas in southwestern China. Indoor air, indoor dust, and personal care product (PCP) samples were collected to evaluate indoor non-dietary MSs exposure in children through various pathways. The concentrations of MSs in indoor environments of industrial areas were approximately one to four orders of magnitude higher than those of residential areas. Sun protection products contained the highest concentrations of MSs. Relatively high levels of cyclic methylsiloxanes (CMSs) were found in plasma of children from industrial areas, which were one to two orders of magnitude higher than those in children from residential areas. The highest MSs levels in plasma were detected in infants (0-1 year), with values of 1.4 × 10² ng/mL and 1.3 × 10² ng/mL for CMSs (D4-D6) and linear methylsiloxanes (LMSs) (L5-L16), respectively. The internal exposure dose of infants in residential areas is driven by major unknown sources of MSs. The average daily doses via inhalation and dust ingestion in children from industrial areas were one to three orders of magnitude higher than in those from residential areas, indicating that these children should be considered a highly exposed population. Inhalation and dust ingestion were both major exposure pathways to MSs for children of all age groups in industrial areas, whereas dermal absorption from PCPs was the predominant exposure pathway for children of all age groups in residential areas (except for infants). Although the exposure risk to D4 and D5 was at an acceptable level for all children studied, the total daily exposure doses of these two cyclic compounds via inhalation for infants in the industrial areas was near the chronic reference dose. Meanwhile, MSs may accumulate in infant plasma within a short period of time (<6 months). Therefore, infants should be the focus of greater attention in future research. As indoor environments may pose high risks for infants in industrial areas, they should be the focus of future research.

Methylsiloxane occurrence and distribution in free-range poultry eggs near a rural industrial park: Indicators of potential risks to birds

The ecological harm from methylsiloxanes has drawn worldwide attention. This study investigated three cyclic (D₄-D₆) and four linear siloxanes (L₇-L₁₀) in the eggs of free-range poultry collected near a rural industrial park in China and found total concentrations in the range of 19.2-1204 (median, 268) ng/g dry weight. Higher concentrations of methylsiloxanes were observed in chicken eggs than duck eggs. Cyclic siloxanes represented a median of 62.2% of the total methylsiloxane concentrations. A source assessment indicated that local soils and outdoor dust were more important sources of egg methylsiloxanes than poultry food. The partitioning of methylsiloxanes between egg yolk and egg albumen was investigated, and preferential distributions of the chemicals in the yolk were observed. This study confirmed that methylsiloxanes were highly prevalent in the study poultry eggs. The results suggested that the potential risks to some wild birds inhabiting this area should be of concern, as their physiologies and feeding ecologies are similar to those of the studied poultry, although available ecotoxicological data of the chemicals to birds remains scarce. Additional research is needed to characterize the accumulation of methylsiloxanes in different bird species and its associated adverse effects on their offspring.

Endocrine disrupting chemicals and breast cancer cells

Many hundreds of endocrine disrupting chemicals (EDCs) have been measured as entering human breast tissue from a range of environmental sources, and this review focuses on discussion of mechanisms by which such EDCs may be contributing to the globally rising incidence of breast cancer. Many of the distinguishing features of breast cancer may be accounted for by EDC exposure, including, but not limited to, the fact that many EDCs possess estrogenic activity and exposure to estrogen is a main risk factor for breast cancer. Studies of the actions of EDCs in human breast cancer cells are aided by use of the conceptual framework of the hallmarks of cancer, and, acting by a variety of genomic and nongenomic mechanisms, EDCs have now been shown to enable all the hallmarks of cancer to develop in human breast cancer cells. Many studies report that hallmarks can develop at concentrations which are within the range of those measured in human breast tissues, especially when added as mixtures. The varied levels of different EDCs measured in individual breast tissue samples together with the overlapping and complementary mechanisms of action of the EDCs imply that thematic mechanisms will be driven inevitably by different chemical mixtures. Despite the complexity, EDCs do need to now be acknowledged as a risk factor for breast cancer in order for preventative strategies to include reduction in EDC exposure.

Bioaccumulation and trophodynamics of cyclic methylsiloxanes in the food web of a large subtropical lake in China

Available information on the bioaccumulation and trophodynamics of cyclic methylsiloxanes in aquatic food webs is insufficient for a reliable understanding of their toxicity and potential ecological harm. The concentrations of four cyclic methylsiloxanes in aquatic species collected from Lake Chaohu (China) were measured and the total concentration was in range of 2.01-36.1 ng/g dry weight. Dodecamethylcyclohexasiloxane (D6) represented 57.7% of the total measured methylsiloxane concentration. The distribution of these methylsiloxanes constitute the first tissue-specific record. The hexamethylcyclotrisiloxane (D3), octamethylcyclotetrasiloxane (D4) and decamethylcyclopentasiloxane (D5) tended to accumulate preferentially in fish muscles, while D6 was preferentially accumulated in fish liver and gills. In Lake Chaohu, significant trophic magnification of D3 (p < 0.01) and dilution of D6 (p < 0.05) were observed, and the trophic magnification factors (TMFs) were estimated at 4.94 and 0.68, respectively. No significant trends in D4 and D5 (p > 0.05) were observed within the food web. This study further confirmed the complexity of trophic transfer of the methylsiloxanes in the aquatic food web. The findings suggest that tissue-specific methylsiloxane distribution in aquatic species might also affect the observed TMFs. More research is required to investigate methylsiloxanes in additional species and their trophodynamics in different food webs.

Methyl siloxanes in road dust from a large silicone manufacturing site in China: implications of human exposure

Methyl siloxanes are becoming increasingly prevalent in the environment because of their extensive use in various consumer products. Little is known about the distribution of these chemicals around factories or their presence in road dust. We conducted a survey of four cyclic (D₃-D₆) and 13 linear (L₄-L₁₆) siloxanes in road dusts around a manufacturing site and found a total siloxane concentration range of 47.3-3.16 × 10³ ng/g (median 372). The predominant siloxanes in the road dust samples were D₃, D₄, D₅, and D₆, with median contributions of 65.3%, 17.9%, 6.36%, and 2.16% of the total siloxane concentrations, respectively. Our reported concentrations were comparable to those found in household dusts in previous studies. No high concentrations of siloxanes were observed in the road dust samples from the manufacturing site, which suggests that siloxanes in outdoor dusts are likely affected by many factors. Under a high exposure scenario, the daily intakes of total siloxanes via road dust ingestion at the 95th percentile were 2.13 and 0.313 ng/kg-bw/day for children and adults, respectively. Although the estimated exposure to siloxanes in outdoor dust for humans was low, more studies on the distributions and risks of siloxanes released from manufacturing sites are needed.

Common garlic (Allium sativum L.) has potent Anti-Bacillus anthracis activity

ETHNOPHARMACOLOGICAL RELEVANCE

Gastrointestinal anthrax, a disease caused by Bacillus anthracis, remains an important but relatively neglected endemic disease of animals and humans in remote areas of the Indian subcontinent and some parts of Africa. Its initial symptoms include diarrhea and stomachache. In the current study, several common plants indicated for diarrhea, dysentery, stomachache or as stomachic as per traditional knowledge in the Indian subcontinent, i.e., Aegle marmelos (L.) Correa (Bael), Allium cepa L. (Onion), Allium sativum L. (Garlic), Azadirachta indica A. Juss. (Neem), Berberis asiatica Roxb. ex DC. (Daruharidra), Coriandrum sativum L. (Coriander), Curcuma longa L. (Turmeric), Cynodon dactylon (L.) Pers. (Bermuda grass), Mangifera indica L. (Mango), Morus indica L. (Black mulberry), Ocimum tenuiflorum L. (Ocimum sanctum L., Holy Basil), Ocimum gratissimum L. (Ram Tulsi), Psidium guajava L. (Guava), Zingiber officinale Roscoe (Ginger), were evaluated for their anti-Bacillus anthracis property. The usage of Azadirachta indica A. Juss. and Curcuma longa L. by Santals (India), and Allium sp. by biblical people to alleviate anthrax-like symptoms is well documented, but the usage of other plants is traditionally only indicated for different gastrointestinal disturbances/conditions.

AIM OF THE STUDY

Evaluate the above listed commonly available edible plants from the Indian subcontinent that are used in the traditional medicine to treat gastrointestinal diseases including those also indicated for anthrax-like symptoms for the presence of potent anti-B. anthracis activity in a form amenable to use by the general population in the endemic areas.

MATERIALS AND METHODS

Aqueous extracts made from fourteen plants indicated above were screened for their anti-B. anthracis activity using agar-well diffusion assay (AWDA) and broth microdilution methods. The Aqueous Garlic Extract (AGE) that displayed most potent anti-B. anthracis activity was assessed for its thermostability, stability under pH extremes encountered in the gastrointestinal tract, and potential antagonistic interaction with bile salts as well as the FDA-approved antibiotics used for anthrax control. The bioactive fractions from the AGE were isolated by TLC coupled bioautography followed by their characterization using GC-MS.

RESULTS

Garlic (Allium sativum L.) extract was identified as the most promising candidate with bactericidal activity against B. anthracis. It consistently inhibited the growth of B. anthracis in AWDA and decreased the viable colony-forming unit counts in liquid-broth cultures by 6-logs within 6-12 h. The AGE displayed acceptable thermostability (>80% anti-B. anthracis activity retained on incubation at 50 °C for 12 h) and stability in gastric pH range (2-8). It did not antagonize the activity of FDA-approved antibiotics used for anthrax control. GC-MS analysis of the TLC separated bioactive fractions of AGE indicated the presence of previously unreported constituents such as phthalic acid derivatives, acid esters, phenyl group-containing compounds, steroids etc. CONCLUSION: The Aqueous Garlic Extract (AGE) displayed potent anti-B. anthracis activity. It was better than that displayed by Azadirachta indica A. Juss. (Neem) and Mangifera indica L., while Curcuma longa L. (Turmeric) did not show any activity under the assay conditions used. Further work should be undertaken to explore the possible application of AGE in preventing anthrax incidences in endemic areas.

Methylsiloxanes in plasma from potentially exposed populations and an assessment of the associated inhalation exposure risk

Methylsiloxanes (MSs) are ubiquitous in indoor air and pose an important health risk. Thus, assessments of indoor inhalation exposure by measuring MSs levels in plasma are needed. In this study, we measured plasma MSs concentrations and evaluated daily indoor inhalation exposure in potentially exposed populations, including residents of industrial areas, university campus, and residential areas, all located in southwestern China. The concentrations of MSs in indoor air (gas-phase and PM_2.5) collected from factory housing and from girls' dormitories on university campus were approximately one to three orders of magnitude higher than in parallel samples from other areas. The consequences of MSs exposure were investigated by measuring MSs levels in the plasma samples of the exposed populations. Relatively high levels of cyclic MSs (CMSs: D4-D6) were found in the plasma of the co-resident family members of factory workers and in female college students living in campus dormitories. The highest levels of CMSs (D4-D6) and linear MSs (L5-L16), 2.3 × 10² and 2.0 × 10² ng/mL, respectively, were detected in the very young (0-3 years old) co-resident children of factory workers. The average daily dose via inhalation (ADD_inh) in different groups showed that the ADD_inh values of all MSs (D4-D6, L5-L16) were one to two orders of magnitude higher in the co-resident family members of factory workers and in female college students than in other groups, indicating that both populations should be considered as potentially highly exposed to MSs. A further assessment showed that inhalation exposure is the main source of CMSs (D4-D6) in plasma for people exposed to high indoor air levels of these compounds. Although the health risk assessment showed that the health risk from inhalation exposure to D4 and D5 was acceptable for all of the studied groups based on the current chronic reference dose (cRfD), the maximum ADD_inh,CMSs value in 0- to 3-year-old children was only 7.9-fold below the cRfD. Because the toxicity of other MSs is unknown, the potential health risk of MSs to very young children via inhalation exposure should be further analysed.

Typical indoor concentrations and mass flow of cyclic volatile methylsiloxanes (cVMSs) in Dalian, China

Cyclic volatile methylsiloxaes (cVMSs), namely hexamethylcyclotrisiloxane (D3), octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5) and dodecamethylcyclohexasiloxane (D6), were studied for a typical indoor environment of male and female dormitories in the campus of Dalian Maritime University (DMU) in China. An empty, frit-fitted SPE cartridge was placed on top of an Isolute ENV + cartridge, sampling cVMSs in particulate and gas phases, respectively. The highest concentration of D3, D4, D5, and D6 was 190, 460, 37,000, and 670 ng m^-3, respectively. All cVMSs, especially D5, were higher in female dormitories than that in male dormitories. Emission rate from different sources of cVMSs in dormitories was calculated from a survey of the use of personal care products (PCPs) by students living in the dormitory during the sampling period. The mean emission rate (ER, mg·d^-1) of D4 and D5 in male dormitories was 0.12 ± 0.01 and 0.49 ± 0.03 mg d^-1, respectively, and that in female dormitories was 0.21 ± 0.05 and 46 ± 17 mg d^-1, respectively. Then, we modified an existing mass balance model to predict the indoor air levels of D4 and D5 in both male and female dormitories based on the usage of PCPs. There was a good agreement for D4 and D5 concentrations in female dormitories between modeled and measured concentrations with the ratio of predicted to measured values to be 1.5 and 1.2, respectively, which indicated that use of PCPs was the main source of cVMSs in university dormitories.

Tube-type passive sampling of cyclic volatile methyl siloxanes (cVMSs) and benzene series simultaneously in indoor air: uptake rate determination and field application

Cyclic volatile methyl siloxanes (cVMSs) and benzene series compounds have attracted increasing attention because they are associated with various adverse health effects. In this study, we developed and validated a novel passive air sampling method (PAS), using Tenax-TA as the sorbent, to measure the concentrations of cVMSs (D4, D5, and D6) and benzene series compounds simultaneously in indoor air. The uptake rates (R), which were calibrated side-by-side by an active air sampling method (Tenax-TA-AAS), ranged from 0.10 to 0.56 mL min-1 depending on chemicals, and the R of the TD tube with Tenax-TA was controlled by the sampler material-side and not the air-side. The passive sampling efficiency (PSE) of styrene and m,p-xylene was close to 1. Based on Pearson correlation analysis, a negative correlation was found between the molecular weight of compounds and their uptake rates. Furthermore, the calibrated Tenax-TA-PAS method was used to quantify cVMSs and benzene series compounds in a living room and an office environment in the urban area of Dalian, China. The concentrations of toluene were the highest in both the living room (10.4 μg m-3) and office (7.02 μg m-3) among the target compounds.

A review of contamination status, emission sources, and human exposure to volatile methyl siloxanes (VMSs) in indoor environments

Siloxanes are organo-silicon compounds containing Si-O-Si linkages and methyl branches. Depending on the structure, siloxanes can be divided into cyclic and linear compounds. Methyl siloxanes with small and medium molecular weights (molecular weights less than 500 g mol^-1), are volatile under normal conditions, and hence are referred to as volatile methyl siloxanes (VMSs). VMSs are additive ingredients in many products such as plastics, rubber, personal care products, and household items. This review provides information on the distribution of VMSs in consumer products, indoor air and dust, and their implications for human exposure. VMSs have been used in personal care products and household items at concentrations on the order of hundreds to thousands of micrograms per gram which are the main sources of contamination in the indoor environments. VMSs have been found widely in indoor air and dust. A significant correlation existed between VMS concentrations in indoor air and dust. Among typical VMSs, dodecamethylcylcopentasiloxane (D5) is the major compound found in indoor environments. The human exposure doses to VMSs through dermal absorption, dust ingestion, and inhalation were compiled; Inhalation is a dominant pathway of exposure to VMSs, especially in indoor environments of occupational settings like hair salons. The human exposure doses were higher in children than in adults.

Releases of Fire-Derived Contaminants from Polymer Pipes Made of Polyvinyl Chloride

In order to assess the human exposure risks from the release of contaminants from water pipes made of polyvinyl chloride (PVC), experiments were carried out by subjecting the PVC pipe material to burning and leaching conditions followed by analysis of the emission and leachate samples. The emissions of burning pipes were analyzed by both infrared spectrometry and gas chromatography-mass spectrometry (GC-MS). The emission test results indicate the presence of chlorinated components including chlorine dioxide, methyl chloride, methylene chloride, allyl chloride, vinyl chloride, ethyl chloride, 1-chlorobutane, tetrachloroethylene, chlorobenzene, and hydrogen chloride were detected in the emissions of burning PVC pipes. Furthermore, the concentrations of benzene, 1,3-butadiene, methyl methacrylate, carbon monoxide, acrolein, and formaldehyde were found at levels capable of affecting human health adversely. The analysis of PVC pipe leachates using GC-MS shows that there are 40-60 tentatively identified compounds, mostly long-chain hydrocarbons such as tetradecane, hexadecane, octadecane, and docosane, were released when the burned PVC materials were soaked in deionized water for one week. Quantitative analysis shows that 2-butoxyethanol, 2-ethyl-1-hexanol, and diethyl phthalate were found in the burned PVC polymer at the average levels of 2.7, 14.0, and 3.1 micrograms per gram (μg/g) of pipe material. This study has significant implications for understanding the benzene contamination of drinking water in the aftermath of wildfires that burned polymer pipes in California.

Assessment of volatile methylsiloxanes in environmental matrices and human plasma

Volatile methylsiloxanes (VMSs) are widely used in various personal-care products and industrial additives and products. This study focused on VMSs exposure in the general population, workers, and the families of workers living in residential and industrial areas of southwestern China. VMSs concentrations in indoor environmental matrices from six industrial facilities were 3.4 × 10² to 9.0 × 10² μg m^-3 in gas-phase samples, 4.7 × 10² to 1.5 × 10⁴ μg g^-1 in PM_2.5 samples, and 2.3 × 10² to 7.2 × 10³ μg g^-1 in dust samples, which were two to four orders of magnitude higher than the concentrations measured in residential areas. Exposure to VMSs was investigated by analysis of plasma samples from workers in residential and industrial areas for the presence of cyclic (D4-D6) and linear (L3-L16) VMSs. VMSs concentrations in plasma samples ranged from 84 to 2.3 × 10² ng ml^-1 in workers, one to two orders of magnitude higher than those in the general population (2.2 ng ml^-1). Daily VMSs indoor exposure via inhalation and ingestion in individuals from residential and industrial areas were estimated and assessed under working-time and leisure-time conditions. This study showed that exposure to VMSs in industrial areas is approximately two to four or one to two orders of magnitude higher than that in residential areas during the working- or leisure-time scenario, respectively. Furthermore, the families of workers (the non-occupational group) experienced higher levels of exposure to VMSs in their homes compared with the general population. The ratios of exposure to linear VMSs via PM_2.5 inhalation to that via the gas phase ranged from 7.8% to 43.1% in industrial areas. This study suggests that intake of linear VMSs via PM_2.5 inhalation should be considered when estimating human exposure to VMSs in areas with high levels of PM_2.5 air pollution.

Biocatalytic solutions to cyclomethicones problem in cosmetics

Silicones are polymers that have properties of great interest for cosmetic and personal care industry, especially D₄ (octamethylcyclotetrasiloxane) and D₅ (decamethylcyclopentasiloxane), generically named cyclomethicones. However, different studies show the hypothesis that the use of these products is harmful and, therefore, several countries have adopted legislative actions to limit their use in personal care and cosmetic products. Faced with this new situation, different cosmetic companies began to look for different alternatives to cyclomethicones, mainly: organomodified silicones or esters. The former are based on the addition of functional groups to the main chain of silicon and oxygen. The latter represent a totally different line, since their functional group is the ester, but they have properties similar to silicones. Esters, especially branched-chain ones are currently the more promising alternative to replace cyclomethicones in cosmetic formulations. Nowadays, most of them are obtained by chemical reactions that require high temperatures and non-selective /contaminant catalysts that lead to low-quality final products. As an alternative, biocatalytic synthesis occurs always at mild operation conditions supplying ultra-pure, odor, and colorless products with less wastes and side reactions. Therefore, biocatalysis is a valid and environmentally sustainable option for the synthesis of silicone-substitute esters used in cosmetic formulations.

Distribution and evaluation of the fate of cyclic volatile methyl siloxanes in the largest lake of southwest China

Cyclic volatile methyl siloxanes (cVMS) used in personal care products are released to aquatic environments through wastewater effluent. cVMS are persistent, toxic, bioaccumulative, and have potential to cause ecological harm. In this study, the environmental behavior of octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5) and dodecamethylcyclohexasiloxane (D6) were evaluated in the largest lake of southwest China, Dian Lake. Air, water and sediment samples were measured for three cVMS compounds in the winter (January) and summer (July) of 2017. In air, D5 exhibited the highest measured mean concentration among the three cVMS, which were 18.4 ± 8.0 ng·m^-3 in winter and 5.78 ± 3.61 ng·m^-3 in summer. In water and sediment, D6 was the cVMS with the highest measured mean concentration. The mean concentrations in water of D6 were 20.8 ± 5.8 ng·L^-1 in winter and 20.4 ± 5.8 ng·L^-1 in summer. The mean concentrations in sediment of D6 were 281 ± 45.8 ng·g^-1 dw in winter and 270 ± 31.3 ng·g^-1 dw in summer. A fugacity-based mass balance chemical fate model for lakes (QWASI) was used for Dian Lake to compare measurements and explore the behavior of cVMS. D6 was predicted to have the highest water column and sediment concentrations. Modeling results showed that most of the D5 and D6 partitioned into sediment and could persist for several years. Persistence was significantly influenced by the high rate of sediment burial. In an analysis of the impact of physicochemical properties and environmental parameters, K_OC was identified as a key parameter for predicting cVMS behavior. This study illustrates the importance of cVMS in sediments and the potential aquatic risk that they may pose.

Marine vegetation analysis for the determination of volatile methylsiloxanes in coastal areas

Volatile methylsiloxanes (VMSs) are massively produced chemicals that comprise a wide range of industrial and household applications. The presence of cyclic and linear VMSs in several environmental matrices and ecosystems indicates persistence associated with a potential of (bio)accumulation and food web transfer with possible toxicological effects. Due to the high anthropogenic pressure in its vicinities particularly in summer, coastal areas in Southern European countries are potential hotspots for the presence of VMSs. The massive afflux of tourists and consequent increase of the use of personal care products (PCPs) with VMSs in their formulations highlight the importance of VMSs assessment in such areas. In this study, different species of marine vegetation (algae and seaweed) were collected in three different geographical areas, covering the Atlantic Ocean (North coast of Portugal), as well as the Mediterranean Sea (coasts of the Region of Murcia, Spain and of the city of Marseille, France). Samples were analysed for the determination of 4 cyclic (D3, D4, D5, D6) and 3 linear (L3, L4, L5) VMSs employing a QuEChERS extraction methodology, followed by gas chromatography/mass spectrometry (GC/MS) quantification. VMSs were detected in 92% of the 74 samples analysed, with the sum of the concentrations per sample ranging from below the limit of detection (LOD) to 458 ± 26 ng·g-1dw (dry weight). A strong predominance of cyclic VMSs over linear ones was verified in almost all samples studied, with D5 and D6 found at higher concentrations. Seasonal variation was also assessed and despite higher levels of VMSs being identified mostly in summer months, clear seasonal trends were not perceived. It was also noted that generally the higher incidence of VMSs occurred in samples from urban and industrialized areas or in the vicinities of WWTPs, suggesting a direct input from these sources in the levels of siloxanes observed.

Pubertal hormones increase hippocampal expression of α4βδ GABAA receptors

CA1 hippocampal expression of α4βδ GABA_A receptors (GABARs) increases at the onset of puberty in female mice, an effect dependent upon the decline in hippocampal levels of the neurosteroid THP (3α-OH-5α-pregnan-20-one) which occurs at this time. The present study further characterized the mechanisms underlying α4βδ expression, assessed in vivo. Blockade of pubertal levels of 17β-estradiol (E₂) (formestane, 0.5 mg/kg, i.p. 3 d) reduced α4 and δ expression by 75-80% (P < 0.05) in CA1 hippocampus of female mice, assessed using Western blot techniques. Conversely, E₂ administration increased α4 and δ expression by 50-100% in adults, an effect enhanced by more than 2-fold by concomitant administration of the 5α-reductase blocker finasteride (50 mg/kg, i.p., 3d, P < 0.05), suggesting that both declining THP levels and increasing E₂ levels before puberty trigger α4βδ expression. This effect was blocked by ICI 182,780 (20 mg/kg, s.c., 3 d), a selective blocker of E₂ receptor-α (ER-α). These results suggest that both the rise in circulating levels of E₂ and the decline in hippocampal THP levels at the onset of puberty trigger maximal levels of α4βδ expression in the CA1 hippocampus.

Cyclic siloxanes in indoor environments from hair salons in Hanoi, Vietnam: Emission sources, spatial distribution, and implications for human exposure

In this study, three typical cyclic siloxanes (CSis) were found in hair care products, indoor dust and indoor air samples at hair salons in Hanoi, Vietnam. The total concentrations of CSis in three kinds of hair care products ranged from 8.77 to 515 μg g^-1. The mean and median concentrations of CSis in dust samples collected at hair salons were 671 and 654 μg g^-1, respectively. The total concentrations of CSis in indoor air samples collected at the hair salons ranged from 415 to 2610 ng m^-3 (mean: 1030; median: 849 ng m^-3, respectively). Among three cyclic siloxanes mentioned in this study, decamethylcyclopentasiloxane (D5) was found at the highest level in all categories of samples. D5 had also a strong correlation between indoor dust and indoor air from hair salons (the coefficient of determination (R²): 0.852); meanwhile dodecamethylcyclohexasiloxane (D6) and octamethylcyclotetrasiloxane (D4) had good correlations (R² = 0.618 and 0.585, respectively). This result indicates that hair care products are main emission source of cyclic siloxanes in indoor environments at the hair salons. The average exposure doses to total SCis through both of dust ingestion and inhalation were estimated to be 103 and 79.5 ng kg-bw^-1 day^-1 for women and men, respectively. These levels were higher than those reported for some Asian countries. This is among the most comprehensive investigations on the emission sources and distributions of cyclic siloxanes in indoor dust and indoor air at hair salons in Vietnam.

Human-relevant potency threshold (HRPT) for ERα agonism

The European Commission has recently proposed draft criteria for the identification of endocrine disrupting chemicals (EDCs) that pose a significant hazard to humans or the environment. Identifying and characterizing toxic hazards based on the manner by which adverse effects are produced rather than on the nature of those adverse effects departs from traditional practice and requires a proper interpretation of the evidence regarding the chemical’s ability to produce physiological effect(s) via a specific mode of action (MoA). The ability of any chemical to produce a physiological effect depends on its pharmacokinetics and the potency by which it acts via the various MoAs that can lead to the particular effect. A chemical’s potency for a specific MoA—its mechanistic potency—is determined by two properties: (1) its affinity for the functional components that comprise the MoA, i.e., its specific receptors, enzymes, transporters, transcriptional elements, etc., and (2) its ability to alter the functional state of those components (activity). Using the agonist MoA via estrogen receptor alpha, we illustrate an empirical method for determining a human-relevant potency threshold (HRPT), defined as the minimum level of mechanistic potency necessary for a chemical to be able to act via a particular MoA in humans. One important use for an HRPT is to distinguish between chemicals that may be capable of, versus those likely to be incapable of, producing adverse effects in humans via the specified MoA. The method involves comparing chemicals that have different ERα agonist potencies with the ability of those chemicals to produce ERα-mediated agonist responses in human clinical trials. Based on this approach, we propose an HRPT for ERα agonism of 1E-04 relative to the potency of the endogenous estrogenic hormone 17β-estradiol or the pharmaceutical estrogen, 17α-ethinylestradiol. This approach provides a practical way to address Hazard Identification according to the draft criteria for identification of EDCs recently proposed by the European Commission.

Permeability of expander breast implants: In vitro and in vivo analyses

INTRODUCTION

The biocompatibility of the polysiloxane breast implant has been studied moderately. The aging of these implants due to lipid penetration and the release of polymerization impurities, such as Platine or octamethylcyclotetrasiloxane (named D4), has already been documented. Since these studies, manufacturing procedures have been improved; thus, the security of breast implants has also improved. Although polymerization and the choice of monomer influence the shell properties, few studies have compared these together in breast implants. Our study compares the permeability and mechanical resistance of 3 breast expander shells after in vivo and in vitro aging.

RESULTS

In vitro, all tested shells quickly sorbed linear molecules, such as fatty acids, and released siloxane impurities. The penetration of a molecule with steric hindrance, such as cholesterol, is slower. Allergan shells have the highest rates of molecule sorption and siloxane release. In vivo, after implantation, Allergan shells lost their initial mechanical properties over time. This observation was not found for mentor shells. For all brands, many biological molecules penetrate the shells, among which cholesterol and fatty acids are always present.

DISCUSSION

The aging of polysiloxane shells depends on the sorption of many biological molecules and the release of siloxane impurities. The siloxanes are impurities and / or degradation products that are due to aging. Moreover, according to our results, the shells act as matrices that separate molecules according to their chemical and physical properties.

CONCLUSION

Not all polysiloxane expander shells have the same properties during aging. The manufacturing procedures and the choice of siloxane monomers are the two most probative factors that explain the observed differences.

Cyclic and linear siloxanes in indoor air from several northern cities in Vietnam: Levels, spatial distribution and human exposure

Earlier studies have reported the occurrence of cyclic and linear siloxanes in personal care and household products. Nevertheless, there is a lack of information on the occurrence of siloxanes in indoor air. In this study, four cyclic and six linear siloxanes were measured in 97 indoor air samples collected from various micro-environments in four cities in northern, Vietnam, during September 2016 to January 2017. The total concentrations of siloxanes (TSi) in particulate and gas phases ranged from 141 to 7220 μg g^-1 (mean: 1880) and 23.8-1580 ng m^-3 (mean: 321), respectively. The total concentrations of cyclic siloxanes (TCSi), linear siloxanes (TLSi), and TSi in indoor air were 1.91-1500 ng m^-3, 21.8-817 ng m^-3, and 41.8-1950 ng m^-3, respectively. The highest mean concentration of siloxanes was found in indoor air from hair salons in Hanoi. The concentrations of siloxanes in air collected from homes in Hanoi were higher than those from other smaller cities such as Bacninh, Thaibinh, and Tuyenquang. The human exposures to siloxanes through inhalation were estimated for various age groups based on the measured concentrations. The mean inhalation exposure doses to total siloxanes for infants, toddlers, children, teenagers, and adults were 352, 219, 188, 132, and 95.9 ng kg-bw^-1 d^-1, respectively.

Toxicology of octamethylcyclotetrasiloxane (D4)

Octamethylcyclotetrasiloxane (D₄) is a volatile cyclic siloxane used primarily as a monomer or intermediate in the production of some silicon-based polymers widely used in industrial and consumer applications and may be present as a residual impurity in a variety of consumer products. A robust toxicological data set exists for D_4. Treatment-related results from a chronic inhalation study conducted in rats are limited to mild effects on the respiratory tract, increases in liver weight, increases in the incidence of uterine endometrial epithelial hyperplasia, and a dose-related trend in the incidence of endometrial adenomas. The observed increases in liver weight appear to be related to the induction of hepatic metabolizing enzymes, similar to those that are induced in the presence of phenobarbital. D₄ is not mutagenic or genotoxic in standard in vitro and in vivo tests; therefore, the benign uterine tumors observed likely occur by a non-genotoxic mechanism. Results from mechanistic studies suggest that D₄ has very weak estrogenic and antiestrogenic activity, as well as dopamine agonist-like activity. In rats, D₄ exposure delays ovulation and hypothesized to prolong exposure of the uterine endometrium to endogenous estrogen. Though this mode of action may play a role in the development of benign uterine tumors in the rat, it is considered unlikely to occur in the human due to the marked differences in cycle regulatory mechanisms. Reproductive effects were observed following D₄ exposure in female rats. These effects appear to be related to a delay of the luteinizing hormone (LH) surge, which fails to induce complete ovulation in the rat. However, based on differences in ovulatory control in rats and humans, it appears these effects may be species-specific with no risk or relevance to human health. Results from pharmacokinetic studies indicate that dermal absorption of D₄ is limited, due to its high volatility and, if absorbed via dermal, oral or inhalation exposure, the majority of D₄ is rapidly cleared from the body, indicating bioaccumulation is unlikely.

Biological relevance of effects following chronic administration of octamethylcyclotetrasiloxane (D4) in Fischer 344 rats

Octamethylcyclotetrasiloxane (D4) is a cyclic siloxane primarily used as a monomer or intermediate in the production of silicone polymers resulting in potential exposure of workers, and potential low level inhalation or dermal exposure for consumers and the general public. Following a two-year inhalation toxicity study with D4 in rats, increases in uterine endometrial cystic hyperplasia and adenomas were observed at the highest concentration of D4 administered (700ppm). No other neoplasms were increased with D4 treatment. In addition, chronic inhalation exposure of rats to D4 induced changes in relative liver and kidney weights, and produced a chronic nephropathy. This manuscript examines the biological relevance and possible modes of action for the effects observed in the F344 rat following chronic inhalation exposure to D4. D4 is not genotoxic and appears to exert its effects through a nongenotoxic mode of action. An alteration in the estrous cycle in the aging F344 rat was the most likely mode of action for the observed uterine effects following chronic inhalation exposure. Data support the conclusion that D4 acts indirectly via a dopamine-like mechanism leading to alteration of the pituitary control of the estrous cycle in aging F344 rats with a decrease in progesterone and an increase in the estrogen/progesterone ratio most likely induced by a decrease in prolactin concentration. D4 also inhibited the pre-ovulatory LH surge causing a delay in ovulation, persistent follicles and thus a prolonged exposure to elevated estrogen in the adult Sprague Dawely rat. A lengthening of the estrous cycle in the F344 rat with an increase in endogenous estrogen was also induced by D4 inhalation. Although the mode of action responsible for induction of uterine adenomas in the female F344 rat has not been clearly confirmed, the subtlety of effects on the effects of D4 on cyclicity may prevent further assessment and definition of the mode of action. The occurrence of uterine endometrial adenoma in the rat is not relevant for human risk characterization because (1) there are differences in ovulatory cycle regulation in rats compared to humans, (2) cystic hyperplasia without atypia in women is not a cancer precursor, and (3) there is no endometrial lesion in women that is directly analogous to endometrial adenoma in the rat. The effects of D4 on liver are due to a phenobarbital-like mechanism that results in induction of cytochrome P450 and other enzymes of xenobiotic biotransformation. The liver effects are adaptive and not adverse. Kidney findings included chonic progressive nephropathy, a rat lesion that has no counterpart in the human and that should not be used in human risk assessment.

Exposure to cyclic volatile methylsiloxanes (cVMS) causes anchorage-independent growth and reduction of BRCA1 in non-transformed human breast epithelial cells

Dermal absorption of components of personal care products (PCPs) may contribute to breast cancer development. Cyclic volatile methylsiloxanes (cVMS) are used widely in the formulation of PCPs, and their presence has been recently detected in human blood. The objectives of this study were to investigate any genotoxic effects after short- (1 week) or longer-term (30 weeks) exposure to hexamethylcyclotrisiloxane (D3), octamethylcyclotetrasiloxane (D4) or decamethylcyclopentasiloxane (D5) in MCF-10 A and MCF-10F immortalized non-transformed human breast epithelial cells. Genotoxic effects were assessed by an ability of cells to grow in suspension culture, from DNA damage measured by comet assays, and from a reduction in levels of DNA repair proteins measured by RT-PCR and western immunoblotting. Dose-dependent anchorage-independent growth in methocel culture was observed after exposure to D3 (10^-13  M-10^-5  M) and D4/D5 (10^-9  M-10^-5  M). DNA damage was measured by the comet assay after 1-h exposure to D3 (10^-6  M-10^-5  M) and D4 (10^-5  M). BRCA1 mRNA and BRCA1 protein levels were reduced after 30-week exposure to 10^-5  M D4 and D5 in both cell lines. Reduced levels of mRNAs for other DNA repair proteins (BRCA2, ATM, ATR, CHK1 and CHK2) were also observed after exposure to 10^-5  M D5 in both cell lines, and some reductions after exposure to D3 and D4. If cVMS can not only enable anchorage-independent growth of non-transformed breast epithelial cells and damage DNA, but also compromise DNA repair systems, then there is the potential for them to impact on breast carcinogenesis. Further risk assessment now requires information concerning the extent to which cVMS may be present in human breast tissues. Copyright © 2016 John Wiley & Sons, Ltd.

Volatile methylsiloxanes in personal care products - Using QuEChERS as a "green" analytical approach

Organosiloxanes, namely volatile methylsiloxanes (VMSs) are one of the most relevant classes of ingredients incorporated in personal care products (PCPs), such as creams and lotions, bath soaps and hair care products. Their use has caused concern among the scientific community due to their potential toxic behaviour to human health and environment. This manuscript reports the first application of QuEChERS ("Quick, Easy, Cheap, Effective, Rugged and Safe") extraction followed by gas chromatography - mass spectrometry analysis to determine VMSs in cosmetics and personal care products. Eight VMSs, four linear (L2-L5) and four cyclic (D3-D6) were investigated in 36 samples. The validated method was able to remove the interfering matrix components, conducting to high recovery percentages (74-104%) and low relative standard deviations (<18%). A linear behaviour was observed in the range of 0.005-2.50mgL(-1) (correlation coefficient, R(2)>0.996) and limits of detection ranged from 0.17ngg(-1) (L2) to 3.75ngg(-1) (L5). Matrix effects were also investigated for all analysed compounds and matrices and showed not to be significant. Global uncertainty of the proposed methodology was also estimated using a bottom-up approach being between 5% and 35% (on average). Finally, the method was satisfactorily applied to the analysis of 36 personal care products. As expected, results showed the existence of VMSs in all analysed samples in concentrations up to 754µgg(-1). D4 and D5 were more frequently detected while body moisturizers, facial creams and shampoos showed the highest levels of VMSs.

Volatile dimethylsiloxanes in market seafood and freshwater fish from the Xúquer River, Spain

Volatile dimethylsiloxanes are a family of synthetic organosilicon-compounds, which have received rising attention because of their widespread use and occurrence in the environment. In the present work, an analytical method based on ultrasound-assisted solid-liquid extraction (USAE) followed by gas chromatography coupled to tandem mass spectrometry (GC-MS/MS) has been optimized and applied to assess the presence of eight volatile dimethyl siloxanes (VMS) (hexamethylcyclotrisiloxane (D3), octamethylcyclotetra-siloxane (D4), decamethylcyclopentasiloxane (D5), dodecamethylcyclohexasiloxane (D6), octamethyltrisiloxane (MDM), decamethyltetrasiloxane (MD2M) and dodecamethylpentasiloxane (MD3M) and tetradecamethylhexasiloxane (MD4M)) in fish. The optimized method presented limits of quantification between 0.1 and 1.3 pg/g for linear volatile dimethylsiloxanes (lVMS) and between 13 and 39 pg/g for cyclic volatile dimethylsiloxanes (cVMS) and intraday relative standard deviation (between 1.9 and 7.0%). Recovery yields were between 71 and 92%. 40 fish samples collected in different markets in Barcelona, (Spain), and 16 samples of fish directly collected at the Xúquer River were analysed. cVMS were detected in almost all the river fish samples at concentrations between pg/g and ng/g, with a significant correlation between the fat content and VMS concentrations in fish. In addition, significant higher concentrations were found in market samples, suggesting sources of contamination from their manipulation and storage in indoor environments. Multivariate analyses were applied to the results and the siloxane profiles and analyte correlations are discussed.

Induction of the Estrogenic Marker Calbindn-D₉k by Octamethylcyclotetrasiloxane

Interrupting the hormonal balance of an organism by interfering with hormones and their target receptors gives rise to various problems such as developmental disorders. Collectively, these reagents are known as endocrine disruptors (EDs). Cyclic volatile methyl siloxanes (cVMSs) are a group of silicone polymers that including octamethylcyclotetrasiloxane (D4). In the present study, we examined the estrogenicity of D4 through in vitro and in vivo assays that employed calcium-binding protein 9K (calbindin-D9k; CaBP-9K) as a biomarker. For in vitro investigation, GH3 rat pituitary cells were exposed to vehicle, 17β-estradiol (E2), or D4 with/without ICI 182 780 (ICI). CaBP-9K and progesterone receptor (PR) both were up-regulated by E2 and D4 which were completely blocked by ICI. Transcription of estrogen receptor α (ER α) was decreased by E2 and D4 but increased by ICI. D4 was also administered to immature female rats for an uterotrophic (UT) assay and detection of CaBP-9K. Ethinyl estradiol (EE) or D4 was administered subcutaneously with or without ICI. Although uterine weight was not significant altered by D4, an effect thought to be due to cytochrome P450 (CYP), it induced CaBP-9K and PR gene expression. Based on these results we reveal that D4 has estrogenic potential proven under in vitro and in vivo experimental conditions.

Distribution, Elimination, and Rearrangement of Cyclic Volatile Methylsiloxanes in Oil-Contaminated Soil of the Shengli Oilfield, China

Cyclic methylsiloxane standards (D4, D5, and D6) and linear methylsiloxanes (L3 through L16) were detected with high total concentrations (from 5.20 × 10(4) to 1.07 × 10(6) ng/g dw) in 18 oil sludge samples collected from the Shengli oilfield during 2008-2013. In 306 soil samples from this oilfield, the mean concentrations (43.4-125 ng/g dw) and the detection frequencies (65-76%) of D4-D6 were 10.9-11.9 and 2.05-2.24 times higher than those in reference soil samples, respectively. The concentrations of total cyclic siloxanes (ΣCyclic) had positive correlations (R(2) = 0.79, p < 0.05) with the total petroleum hydrocarbons concentration (TPH) in soil, indicating that oil production could release cyclic siloxanes to the environment. During 2008-2013, an increasing tendency (mean of 13.4% per annum) of ΣCyclic was found in soil with high TPH (>5000 mg/kg) but was not found in soil with lower TPH. Elimination experiments showed that petroleum hydrocarbons could reduce the degradation and volatilization rates of D4, D5, and D6 in impacted oilfield soil. The half-lives of D4, D5, and D6 in the opened and capped soil systems with TPH = 400-40 000 mg/kg were 1.19-22.2 and 1.03-7.43 times larger than those in common soil (TPH = 80 mg/kg), respectively. Furthermore, the petroleum hydrocarbons could affect the rearrangement-reaction rates of D5 and D6 in soil.