Full life-cycle toxicity assessment on triclosan using rotifer Brachionus calyciflorus

Effects of triclosan on lipid metabolism and underlying mechanisms in the cyprinid fish Squalidus argentatus

The ubiquitous presence of the disinfectant triclosan (TCS) has raised global concerns regarding its potential threat to aquatic organisms. However, the effects of TCS on lipid metabolism in fish and its underlying mechanisms remain unclear. This study investigated the effect of environmentally relevant levels of TCS on the lipid metabolism in the cyprinid fish Squalidus argentatus. Our results showed that the lipid metabolism in the cyprinid fish S. argentatus was perturbed by 28-day exposure to TCS, as evidenced by higher levels of lipid accumulation in both the liver and blood. To elucidate the mechanisms underlying toxicity, we evaluated oxidative stress, inflammatory status, and lipase activity in the liver. Our findings indicated increased ROS-specific fluorescence intensity, superoxide dismutase (SOD) activity, and malondialdehyde (MDA) content in the livers of S. argentatus exposed to TCS, suggesting oxidative damage. Additionally, TCS treatment induced the production of proinflammatory cytokines in the liver of S. argentatus exposed to TCS, which suppressed hepatic lipase activity. Intestinal tissue morphology, inflammation, and blood lipopolysaccharide (LPS) levels were also examined. Significant increases in goblet cell count and MDA levels were observed in the intestinal tract. After 28 days of TCS exposure, the serum LPS levels were significantly elevated. 16S rRNA sequencing was conducted to analyze the effects of TCS on the diversity and composition of the intestinal microbiota. Transcriptomic analysis was performed to reveal global molecular alterations following TCS exposure. In conclusion, our results indicate that TCS may disrupt the lipid metabolism in S. argentatus by (i) inducing hepatic oxidative stress and inflammation, which suppress lipoprotein lipase activity, (ii) affecting the production of beneficial metabolites and endotoxins by dysregulating gut microbiota composition, and (iii) altering the expression levels of lipid metabolism-related pathways.

Toxic effects of fragmented polyethylene terephthalate particles on the marine rotifer Brachionus koreanus: Based on ingestion and egestion assay, in vivo toxicity test, and multi-omics analysis

Microplastics (MPs) are a major concern in marine ecosystem because MPs are persistent and ubiquitous in oceans and are easily consumed by marine biota. Although many studies have reported the toxicity of MPs to marine biota, the toxicity of environmentally relevant types of MPs is little understood. We investigated the toxic effects of fragmented polyethylene terephthalate (PET) MP, one of the most abundant MPs in the ocean, on the marine rotifer Brachionus koreanus at the individual and molecular level. No significant rotifer mortality was observed after exposure to PET MPs for 24 and 48 h. The ingestion and egestion assays showed that rotifers readily ingested PET MPs in the absence of food but not when food was supplied; thus, there were also no chronic effects of PET MPs. In contrast, intracellular reactive oxygen species levels and glutathione S-transferase activity in rotifers were significantly increased by PET MPs. Transcriptomic and metabolomic analyses revealed that genes and metabolites related to energy metabolism and immune processes were significantly affected by PET MPs in a concentration-dependent manner. Although acute toxicity of PET MPs was not observed, PET MPs are potentially toxic to the antioxidant system, immune system, and energy metabolism in rotifers.

Critical review on the environmental behaviors and toxicity of triclosan and its removal technologies

As a highly effective broad-spectrum antibacterial agent, triclosan (TCS) is widely used in personal care and medical disinfection products, resulting in its widespread occurrence in aquatic and terrestrial environments, and even in the human body. Notably, the use of TCS surged during the COVID-19 outbreak, leading to increasing environmental TCS pollution pressure. From the perspective of environmental health, it is essential to systematically understand the environmental occurrence and behavior of TCS, its toxicological effects on biota and humans, and technologies to remove TCS from the environment. This review comprehensively summarizes the current knowledge regarding the sources and behavior of TCS in surface water, groundwater, and soil systems, focusing on its toxicological effects on aquatic and terrestrial organisms. Effluent from wastewater treatment plants is the primary source of TCS in aquatic systems, whereas sewage application and/or wastewater irrigation are the major sources of TCS in soil. Human exposure pathways to TCS and associated adverse outcomes were also analyzed. Skin and oral mucosal absorption, and dietary intake are important TCS exposure pathways. Reducing or completely degrading TCS in the environment is important for alleviating environmental pollution and protecting public health. Therefore, this paper reviews the removal mechanisms, including adsorption, biotic and abiotic redox reactions, and the influencing factors. In addition, the advantages and disadvantages of the different techniques are compared, and development prospects are proposed. These findings provide a basis for the management and risk assessment of TCS and are beneficial for the application of treatment technology in TCS removal.

Toxic effects of triclosan in aquatic organisms: A review focusing on single and combined exposure of environmental conditions and pollutants

Triclosan (TCS) is an antibacterial agent commonly used in personal care products. Due to its widespread use and improper disposal, it is also a pervasive contaminant, particularly in aquatic environments. When released into water bodies, TCS can induce deleterious effects on developmental and physiological aspects of aquatic organisms and also interact with environmental stressors such as weather, metals, pharmaceuticals, and microplastics. Multiple studies have described the adverse effects of TCS on aquatic organisms, but few have reported on the interactions between TCS and other environmental conditions and pollutants. Because aquatic environments include a mix of contaminants and natural factors can correlate with contaminants, it is important to understand the toxicological outcomes of combinations of substances. Due to its lipophilic characteristics, TCS can interact with a wide range of substances and environmental stressors in aquatic environments. Here, we identify a need for caution when using TCS by describing not only the effects of exposure to TCS alone on aquatic organisms but also how toxicity changes when it acts in combination with multiple environmental stressors.

Variations in life history parameters, population dynamics, and transcriptome regulation of Brachionus plicatilis exposed to triclosan

Triclosan (TCS) poses an ecological health risk due to its lipophilic nature, long half-life, and bioconcentration. To evaluate the toxicity of TCS on aquatic organisms, the life history parameters, population dynamics, and transcriptome regulation of Brachionus plicatilis exposed to TCS were investigated. In this study, the fecundity of rotifers was promoted by 25 μg/L of TCS and inhibited by higher concentrations (100 μg/L, 200 μg/L). The reproductive period of rotifers was shortened by 46.24 % but the post-reproductive period was prolonged by 176.47 % in 200 μg/L TCS. Both population growth and life table parameters indicated that a high concentration of TCS (200 μg/L) had negative impacts on population growth. Transcriptomic analysis showed that the effects of TCS on the life history parameters and population dynamics of rotifers were determined by regulating the expression of functional genes in cilium organization and cilium assembly and involved in pathways of focal adhesion.

Toxicity of triclosan, an antimicrobial agent, to a nontarget freshwater zooplankton species, Moina macrocopa

The toxicity of triclosan (TCS) on the freshwater cladoceran Moina macrocopa was investigated by acute and chronic toxicity assessments followed by genotoxicity and oxidative stress response analyses. The 48-h LC50 of TCS for ≤24-h-old M. macrocopa was determined as 539 μg L-1 . Chronic exposure to TCS at concentrations ranging from 5 to 100 μg L-1 showed a stimulatory effect at low concentrations (≤10 μg L-1 ) and an inhibitory effect at high concentrations (≥50 μg L-1 ) on growth, reproduction, and population-growth-related parameters of M. macrocopa. The genotoxicity test results indicated that TCS concentrations ranging from 50 to 100 μg L-1 can alter individuals' DNA. Analysis of the antioxidant enzymes catalase (CAT) and glutathione s-transferase (GST) demonstrated increased levels of these enzymes at high TCS concentrations. Our results indicated that TCS concentrations found in the natural environment have minimal acute toxicity to M. macrocopa. However, TCS at even low concentrations can significantly affect its growth, reproduction, and population-growth-related characteristics. The observed responses suggest a hormetic dose-response pattern and imply a potential endocrine-disrupting effect of TCS. Our molecular and biochemical findings indicated that high concentrations of TCS have the potential to induce oxidative stress that may lead to DNA alterations in M. macrocopa.

Soil pH influences the toxicity of Basamid® eluates to non-target species of primary consumers

Basamid® is a fumigant nematicide and fungicide known to break down in several volatile compounds, mainly methyl isothiocyanate (MITC), when in contact with water. Soil abiotic parameters, such as pH, influences this breakdown process, and thus, the toxic effects of Basamid® to aquatic biota. This work studied the influence of soil pH (5.5, 6.5 and 7.5) on the toxicity of eluates (1:4, m:v), obtained from Basamid®-contaminated soils (with the recommended dose of 145 mg of dazomet/Kg of soil), on two primary consumers: Daphnia magna and Brachionus calyciflorus. For this, lethal and sublethal toxicity of eluates originated from soils at pH 5.5, 6.5 and 7.5, contaminated with Basamid® (Ba-E 5.5; 6.5 and 7.5, respectively), were assessed (dilutions between 0.096 - 100%). The LD50,24h of Basamid® eluates for D. magna varied from 3.07% to 7.82% (Ba-E 6.5 and Ba-E 5.5 respectively), while for B. calyciflorus varied from 18.1% to 84.7% (Ba-E 6.5 and Ba-E 7.5, respectively). Both species were less sensitive to Basamid® eluates originated from soils with pH 7.5 and more sensitive to those obtained from soils with pH 6.5. Regarding the sublethal effects, a lower soil pH was associated with a higher toxicity of Basamid® to D. magna reproduction (LOED: 0.125% Ba-E 5.5), while for B. calyciflorus such a higher toxicity was observed at the highest soil pH (ED20: 7.42% [5.10-9.74] at Ba-E 7.5). These results show a negative association between soil pH and the lethal toxicity of Basamid® contaminated eluates. However, such a pattern was not observed at sublethal level, at which a species dependency was observed regarding the influence of soil pH in the observed toxicity. Nevertheless, it is to highlight that very low concentrations of eluates (as 3.07%) caused significant mortality, indicating a high risk for freshwater biota. Considering that Basamid® is likely to reach the aquatic systems is real, for which reason the recommended dose must be reviewed at environmentally-relevant scenarios.

Triclosan and related compounds in the environment: Recent updates on sources, fates, distribution, analytical extraction, analysis, and removal techniques

Triclosan (TCS) has been widely used in daily life because of its broad-spectrum antibacterial activities. The residue of TCS and related compounds in the environment is one of the critical environmental safety problems, and the pandemic of COVID-19 aggravates the accumulation of TCS and related compounds in the environment. Therefore, detecting TCS and related compound residues in the environment is of great significance to human health and environmental safety. The distribution of TCS and related compounds are slightly different worldwide, and the removal methods also have advantages and disadvantages. This paper summarized the research progress on the source, distribution, degradation, analytical extraction, detection, and removal techniques of TCS and related compounds in different environmental samples. The commonly used analytical extraction methods for TCS and related compounds include solid-phase extraction, liquid-liquid extraction, solid-phase microextraction, liquid-phase microextraction, and so on. The determination methods include liquid chromatography coupled with different detectors, gas chromatography and related methods, sensors, electrochemical method, capillary electrophoresis. The removal techniques in various environmental samples mainly include biodegradation, advanced oxidation, and adsorption methods. Besides, both the pros and cons of different techniques have been compared and summarized, and the development and prospect of each technique have been given.

Inhibitory Effects of Antipsychotic Chlorpromazine on the Survival, Reproduction and Population Growth Other Than Neurotransmitters of Zooplankton in Light of Global Warming

Global warming and environmental pollution have created a unique combination of abiotic and biotic stresses to zooplankton. However, little information is available on the effects of antipsychotic drugs commonly used to treat psychosis, such as chlorpromazine (CPZ), on non-target aquatic organisms in light of global warming. This study investigated how dopamine concentrations (DAC), acute toxicity and chronic toxicity of Brachionus calyciflorus changed in response to CPZ and gradually increasing temperatures. The results showed that the concentration range of rotifer DAC was 1.06~2.51 ng/g. At 18, 25 and 32 °C, the 24 h LC50 was 1.795, 1.242 and 0.833 mg/L, respectively. Compared to the control, exposure to CPZ significantly decreased life expectancy at hatching, the net reproduction rate, generation time, population growth rate and dopamine concentration of B. calyciflorus in all three temperatures (p < 0.05). The toxicity of CPZ to rotifers was increased by high temperature. These findings indicated that CPZ is highly toxic to rotifers, displaying high ecological risks to aquatic ecosystems.

Effect of chloramphenicol on the life table demography of Brachionus calyciflorus (Rotifera): A multigenerational study

During the last two decades, there has been increasing concerns about the presence of antibiotics in aquatic environments. Phenicol antibiotics, such as chloramphenicol (CMP), commonly used in the veterinary and aquaculture fields to treat infections, have been often detected in aquatic environments, but scarce ecotoxicity information regarding the effects of CMP on non-target aquatic organisms is available, and multigenerational studies are seldom studied. Here we quantified the demographic responses of Brachionus calyciflorus exposed to sublethal concentrations (0, 5, 10, 30, 50, 70 and 90 mg L^-1) of CMP for three successive generations (P0, F1, and F2). Our results showed that compared to the control, higher concentrations of CMP significantly decreased the life expectancy at hatching, generation time, net reproductive rate and intrinsic rate of population increase in all three generations, and the proportion of mictic offspring in the F1 generation of B. calyciflorus. With increasing generations, higher concentrations of CMP showed increased toxic effects on life expectancy at hatching and net reproductive rate, but irregular negative effects on generation time, intrinsic rate of population increase, and proportion of mictic offspring of the rotifers. These results indicate that multigenerational studies are necessary to prevent insufficient assessments of the impact of antibiotics in aquatic ecosystems.

Alternative animal models in predictive toxicology

Toxicity testing relies heavily on animals, especially rodents as part of the non-clinical laboratory testing of substances. However, the use of mammalians and the number of animals employed in research has become a concern for institutional ethics committees. Toxicity testing involving rodents and other mammals is laborious and costly. Alternatively, non-rodent models are used as replacement, as they have less ethical considerations and are cost-effective. Of the many alternative models that can be used as replacement models, which ones can be used in predictive toxicology? What is the correlation between these models and rodents? Are there standardized protocols governing the toxicity testing of these commonly used predictive models? This review outlines the common alternative animal models for predictive toxicology to address the importance of these models, the challenges, and their standard testing protocols.

Sediment from lake with missing egg bank is toxic to hatchlings of model zooplankton: A reason to consider obligate dormancy in toxicological assessment

Over the last 60 years, valuable progress was made in the standardization of environmental monitoring with model zooplankton. However, obligate dormancy in zooplankton life cycles is not yet considered in standardized toxicology methods. Most zooplankton from coastal and inland waters use dormancy as a critical ecological strategy, and exposure to toxicants during dormancy or resurrection from dormancy alters developmental patterning and hatching success. The present study accounts for this by using both standardized and novel toxicology assays to assess the impacts of coal ash contaminated sediments and water on development, hatching, and survivorship of model zooplankton. The results demonstrate that standardized assays with rotifer and cladoceran models detect no toxicity in surface water and sediment pore water from Lake Sutton, North Carolina, USA. By contrast, novel toxicity assays with cladoceran and anostracan models demonstrate that development and larval survivorship are negatively impacted by Lake Sutton water and sediment. Embryos of Artemia franciscana display developmental patterning and hatching aberrations that match those observed in previous studies with metals when hatched in filtered surface water or pore water after a period of anoxia-induced dormancy. Larval survivorship in Daphnia magna and A. franciscana also decreases when post-diapause embryos are hatched in the presence of sediment. The effects of whole sediment on larval survivorship are not explained by coal ash impacts on water pH. These data provide an explanation for the missing egg bank and historic community restructure in Lake Sutton. The data also demonstrate a need for standardized assays that include dormant life stages.

Chronic Effects of Bromate on Sexual Reproduction of Freshwater Rotifer Brachionus calyciflorus

The effects of potassium bromate (KBrO₃), sodium bromate (NaBrO₃), and potassium bromide (KBr) on the sexual reproduction of the rotifer Brachionus calyciflorus were studied by 2-d population growth, 4-d sexual reproduction, and 7-d resting egg production tests. The results showed that low concentrations of bromate promote 2-d and 4-d rotifer population growth, while high concentrations limit it. Bromate stress significantly affected parameters of rotifer sexual reproduction, including the ratio of mictic to amictic females, the mictic rate of rotifers, and the fertilization rate of mictic females. KBrO₃ at 0.001, 0.01, 1, and 10 mg/L, NaBrO₃ at 1 and 10 mg/L, and KBr at 100 and 200 mg/L significantly increased resting egg production, while KBrO₃ at 100 and 200 mg/L, and NaBrO₃ at 200 mg/L significantly decreased it. Resting egg production appears to provide a sensitive endpoint in evaluating the effect of bromate on rotifer sexual reproduction.

Biomarkers for the toxicity of sublethal concentrations of triclosan to the early life stages of carps

Accumulation, contents of protein, non-enzymatic antioxidant glutathione (GSH and GSSG), lipid peroxidation product (melondialdehyde-MDA) and organic acids (fumarate, succinate, malate and citrate), and activities of neurological (acetylcholinesterase-AChE), detoxification (glutathione S-transferase-GST) and metabolic (lactate dehydrogenase-LDH, aspartate transaminase-AST and alanine transaminase-ALT) enzymes were recorded in the hatchlings of Cyprinus carpio, Ctenopharyngodon idella, Labeo rohita and Cirrhinus mrigala after 7 and 14 days exposure and 10 days post exposure (recovery period) to sublethal concentrations (0.005, 0.01, 0.02 and 0.05 mg/L) of triclosan, a highly toxic and persistent biocide used in personal care products. Accumulation was maximum between 7-14 days at 0.01 mg/L for C. carpio and L. rohita but at 0.005 mg/L for C. idella and C. mrigala. No triclosan was observed at 0.005 mg/L in C. carpio and C. mrigala after recovery. Significant decline in protein, glutathione and acetylcholinesterase but increase in glutathione S-transferase, lactate dehydrogenase, aspartate transaminase, alanine transaminase, melondialdehyde and organic acids over control during exposure continued till the end of recovery period. Integrated biomarker response (IBR) analysis depicted higher star plot area for glutathione and glutathione S-transferase during initial 7 days of exposure, thereafter, during 7-14 days of exposure and the recovery period, higher star plot area was observed for acetylcholinesterase, aspartate transaminase, alanine transaminase and organic acids. Higher star plot area was observed for protein in all the species throughout the study. The study shows that L. rohita is most sensitive and glutathione, acetylcholinesterase, aspartate transaminase and alanine transaminase are the biomarkers for the toxicity of sublethal concentrations of TCS.

Embryo bioassays with aquatic animals for toxicity testing and hazard assessment of emerging pollutants: A review

This review article gathers the available information on the use of embryo-tests as high-throughput tools for toxicity screening, hazard assessment and prioritization of new and existing chemical compounds. The approach is contextualized considering the new legal trends for animal experimentation, fostering the 3R policy, with reduction of experimental animals, addressing the potential of embryo-tests as high-throughput toxicity screening and prioritizing tools. Further, the current test guidelines, such as the ones provided by OECD and EPA, focus mainly in a limited number of animal lineages, particularly vertebrates and arthropods. To extrapolate hazard assessment to the ecosystem scale, a larger diversity of taxa should be tested. The use of new experimental animal models in toxicity testing, from a representative set of taxa, was thoroughly revised and discussed in this review. Here, we critically review current tools and the main advantages and drawbacks of different animal models and set researcher priorities.

Joint toxic effects of cadmium and four pesticides on the earthworm (Eisenia fetida)

The contaminants, instead of single contaminants, are usually found as chemical mixtures in terrestrial environment. However, little information is now available about the joint effects of heavy metals and farm chemicals on the soil organism. Our current study aimed to assess the combined toxicity of cadmium (Cd) and four pesticides (atrazine, chlorpyrifos, lambda-cyhalothrin and abamectin) to the earthworm (Eisenia fetida) with binary, ternary, quaternary and quinquenary mixtures. Two distinct kinds of bioassay systems were applied in this study, including contact filter paper test and artificial soil test. Synergistic effects were observed from two quaternary mixtures (Cd-Atrazine-Chlorpyrifos-Lambda-cyhalothrin and Cd-Chlorpyrifos-Lambda-cyhalothrin-Abamectin) and one quinquenary mixture (Cd-Atrazine-Chlorpyrifos-Lambda-cyhalothrin-Abamectin) in both bioassay systems. Besides, two binary mixtures (Cd-Atrazine and Cd-Lambda-cyhalothrin) and three ternary mixtures (Cd-Atrazine-Chlorpyrifos, Cd-Atrazine-Lambda-cyhalothrin and Cd-Chlorpyrifos-Lambda-cyhalothrin) also exhibited synergistic effects on E. fetida by the soil toxicity test. It is more practical to evaluate the contaminant toxicities to earthworm by soil toxicity test. Therefore, the effects of chemical mixtures on soil invertebrates might be underestimated by data obtained from single toxicant. Our findings would offer a better understanding of the complex effects of chemical mixtures on non-target living creatures, and these findings provided valuable insights into the interplay of different chemicals in natural environment.

Adverse effects of the insecticides chlordecone and fipronil on population growth and expression of the entire cytochrome P450 (CYP) genes in the freshwater rotifer Brachionus calyciflorus and the marine rotifer Brachionus plicatilis

Chlordecone and fipronil are used as an insecticide and have been widely detected in the aquatic environments. However, their toxicity is still poorly investigated in aquatic invertebrates. In this study, we examined effects of chlordecone and fipronil on population growth and transcriptional regulation of the entire cytochrome P450 (CYP) genes in the freshwater rotifer Brachionus calyciflorus and the marine rotifer B. plicatilis. In B. calyciflorus, a 24 h-no observed effect concentration (NOEC-24 h) and a 24 h-median lethal concentration (LC50-24 h) of chlordecone were determined as 100 μg/L and 193.8 μg/L, respectively, while NOEC-24 h and LC50-24 h of fipronil were determined as 1000 μg/L and 2033.0 μg/L, respectively. In B. plicatilis, NOEC-24 h and LC50-24 h of chlordecone were 100 μg/L and 291.0 μg/L, respectively, while NOEC-24 h and LC50-24 h of fipronil were determined as 1000 μg/L and 5735.0 μg/L, respectively. Moreover, retardation in the population growth were observed in response to chlordecone and fipronil in both rotifer species, suggesting that chlordecone and fipronil have a potential adverse effects on life cycle parameters of two rotifer species. Additionally, modulation in the expressions of the entire CYP genes were demonstrated in response to chlordecone and fipronil at 24 h period. These results provide the better understanding on how chlordecone and fipronil can affect in population growth of two rotifers and CYP gene expressions in chlordecone- and fipronil-exposed rotifers.

Fate and effects of sediment-associated triclosan in subtropical freshwater microcosms

Triclosan (TCS) is an antibacterial agent that is commonly used in personal care products. Because of its sediment-binding properties, TCS exposure presents a potential threat to sediment-dwelling aquatic organisms. Currently our knowledge of the fate and effects of sediment-associated TCS in aquatic systems is limited. To understand the impact of sediment-associated TCS, we used microcosms to assess effects of TCS exposure on a diverse range of organisms selected to mimic a subtropical community, with an exposure period of 28 days. We included the oligochaete freshwater worm Limnodrilus hoffmeisteri to evaluate the interaction between sediment-associated TCS and sediment-dwelling organisms, including potential loss of TCS from the sediment due to biological activity and bioaccumulation. Benthic macroinvertebrate presence significantly increased the TCS levels from 0.013 ± 0.007 μg/L to 0.613 ± 0.030 μg/L in the overlying water through biological activity, posing a potential additional risk to pelagic species, but it did not result in a significant reduction of the sediment concentration. Furthermore, worms accumulated TCS with estimated Biota-Sediment-Accumulation-Factors (BSAFs) ranging between 0.38-3.55. Other than for algae, TCS at environmental concentrations did not affect the survival of the introduced organisms, including the L. hoffmeisteri. Our results demonstrate that, although TCS at currently detected maximum concentration may not have observable toxic effects on the benthic macroinvertebrates in the short term, it can lead to bioaccumulation in worms.

The toxicity of a mixture of two antiseptics, triclosan and triclocarban, on reproduction and growth of the nematode Caenorhabditis elegans

Many widely used healthcare products contain antiseptics, whose persistence in aquatic environments, soils, and sediments leads to the contamination of ecosystems and adversely affects wildlife. Recently, the impact not only of high but also low doses of contaminants and mixtures of several chemicals has become a focus of concern. In this study, toxicity tests of the antiseptics triclosan (TCS) and triclocarban (TCC) were performed in an aquatic test medium using the nematode Caenorhabditis elegans. Nominal concentrations of TCS and TCC were tested in separate single-substance toxicity tests (96-h-exposure), focussing on growth and reproduction endpoints. Median effective concentrations (EC50s) from the single-substance tests were subsequently used to set up five different ratios of TCS:TCC mixtures leading to the same toxicity. Six dilutions of each mixture ratio were tested for effon reproduction of C. elegans. In the single-substance tests, TCC was about 30 times more toxic than TCS when considering effects on growth and concerning reproduction, TCC was about 50 times more toxic than TCS. For both substances, the toxic effect on reproduction was more pronounced than the one on growth. Low doses of TCS (1-10 µmol L^-1) stimulated reproduction by up to 301% compared to the control, which might be due to endocrine disruption or other stress-related compensation responses (hormesis). Neither antiseptic stimulated growth. In the mixtures, increasing amounts of TCC inhibited the stimulatory effects of TCS on reproduction. In addition, the interactions of TCS and TCC were antagonistic, such that mixtures displayed lower toxicity than would have been expected when TCS and TCC mixtures adhered to the principle of concentration addition.

Multigenerational effects of triclosan on the demography of Plationus patulus and Brachionus havanaensis (ROTIFERA)

Triclosan is a personal care product widely used in North America, Europe and Asia as antimicrobial ingredient in many consumer chemical products. In Mexico concentrations of triclosan have been reported in aquatic systems. However, there is no law regulating the presence of chemicals such as triclosan, in aquatic systems. The scarce data about this chemical has increased concern among ecotoxicologists regarding possible effects on aquatic organisms. Moreover, multigenerational studies are rarely studied and the results vary depending on the contaminant. Rotifers, are a dominant group of zooplankton, and have been used in aquatic risk assessments of personal care products due to their sensitivity and high reproductive rates. Plationus patulus and Brachionus havanaensis are common rotifers distributed in aquatic ecosystems of Mexico and have been used in ecotoxicological bioassays. In this study, the median lethal concentration (LC50, 24h) of P. patulus and B. havanaensis exposed to triclosan was determined. Based on the LC50, we tested three sublethal concentrations of triclosan to quantify the demographic responses of both rotifers for two successive generations (F0, and F1). The 24h LC50 of triclosan for P. patulus and B. havanaensis were 300 and 500µgL^-1 respectively. Despite the concentration, triclosan had an adverse effect on both Plationus patulus and Brachionus havanaensis in both generations exposed. Experiments show that P. patulus was more sensitive than B. havanaensis when exposed to triclosan. When exposed to triclosan the parental generation (F0) of P. patulus was far more affected than F1.

Effects of testosterone and flutamide on reproduction in Brachionus calyciflorus

The effects of testosterone and flutamide on reproduction in Brachionus calyciflorus were studied. Asexual reproduction in B. calyciflorus was not affected by testosterone at different concentrations of flutamide. Flutamide in combination with 0, 25, 50, or 75 µg L-1 testosterone had a significant effect on mixis rate. The combination of 5 µg L-1 flutamide with 25 µg L-1 or 50 µg L-1 testosterone resulted in a mixis rate that was 2.2× lower than that with flutamide alone. Fertilization rate was significantly decreased by 7.5 µg L-1 flutamide in combination with 25, 50, or 75 µg L-1 testosterone. The number of resting eggs produced per mictic female was significantly lower at all concentrations of testosterone. A low concentration of flutamide in combination with testosterone resulted in antagonism, increasing the number of resting eggs produced. However, when testosterone was combined with a higher concentration of flutamide, resting egg production declined. Therefore, long-term exposure to either testosterone, flutamide, or a combination of these two compounds may significantly reduce resting egg production in rotifers. This implies that resting egg production is affected differently by hormone pathways.

Triclosan exposure, transformation, and human health effects

Triclosan (TCS) is an antimicrobial used so ubiquitously that 75% of the US population is likely exposed to this compound via consumer goods and personal care products. In September 2016, TCS was banned from soap products following the risk assessment by the US Food and Drug Administration (FDA). However, TCS still remains, at high concentrations, in other personal care products such as toothpaste, mouthwash, hand sanitizer, and surgical soaps. TCS is readily absorbed into human skin and oral mucosa and found in various human tissues and fluids. The aim of this review was to describe TCS exposure routes and levels as well as metabolism and transformation processes. The burgeoning literature on human health effects associated with TCS exposure, such as reproductive problems, was also summarized.

Triclosan: A review on systematic risk assessment and control from the perspective of substance flow analysis

Triclosan (TCS) is a broad spectrum antibacterial agent mainly used in Pharmaceutical and Personal Care Products. Its increasing use over recent decades have raised its concentration in the environment, with commonly detectable levels found along the food web-from aquatic organisms to humans in the ecosystem. To date, there is shortage of information on how to investigate TCS's systematic risk on exposed organisms including humans, due to the paucity of systematic information on TCS flows in the anthroposphere. Therefore, a more holistic approach to mass flow balancing is required, such that the systematic risk of TCS in all environmental matrices are evaluated. From the perspective of Substance Flow Analysis (SFA), this review critically summarizes the current state of knowledge on TCS production, consumption, discharge, occurrence in built and natural environments, its exposure and metabolism in humans, and also the negative effects of TCS on biota and humans. Recent risk concerns have mainly focused on TCS removal efficiencies and metabolism, but less attention is given to the effect of mass flows from source to fate during risk exposure. However, available data for TCS SFA is limited but SFA can derive logical systematic information from limited data currently available for systematic risk assessment and reduction, based on mass flow analysis. In other words, SFA tool can be used to develop a comprehensive flow chart and indicator system for the risk assessment and reduction of TCS flows in the anthroposphere, thereby bridging knowledge gaps to streamline uncertainties related to policy-making on exposure pathways within TCS flow-lines. In the final analysis, specifics on systematic TCS risk assessment via SFA, and areas of improvement on human adaptation to risks posed by emerging contaminants are identified and directions for future research are suggested.