Triclosan: Environmental exposure, toxicity and mechanisms of action

ArticleinJournal of Applied Toxicology 31(4):285-311 · May 2011with342 Reads
DOI: 10.1002/jat.1660 · Source: PubMed
Abstract
Triclosan [5-chloro-2-(2,4-dichlorophenoxy)phenol; TCS] is a broad spectrum antibacterial agent used in personal care, veterinary, industrial and household products. TCS is commonly detected in aquatic ecosystems, as it is only partially removed during the wastewater treatment process. Sorption, biodegradation and photolytic degradation mitigate the availability of TCS to aquatic biota; however the by-products such as methyltriclosan and other chlorinated phenols may be more resistant to degradation and have higher toxicity than the parent compound. The continuous exposure of aquatic organisms to TCS, coupled with its bioaccumulation potential, have led to detectable levels of the antimicrobial in a number of aquatic species. TCS has been also detected in breast milk, urine and plasma, with levels of TCS in the blood correlating with consumer use patterns of the antimicrobial. Mammalian systemic toxicity studies indicate that TCS is neither acutely toxic, mutagenic, carcinogenic, nor a developmental toxicant. Recently, however, concern has been raised over TCS's potential for endocrine disruption, as the antimicrobial has been shown to disrupt thyroid hormone homeostasis and possibly the reproductive axis. Moreover, there is strong evidence that aquatic species such as algae, invertebrates and certain types of fish are much more sensitive to TCS than mammals. TCS is highly toxic to algae and exerts reproductive and developmental effects in some fish. The potential for endocrine disruption and antibiotic cross-resistance highlights the importance of the judicious use of TCS, whereby the use of TCS should be limited to applications where it has been shown to be effective.
    • "Furthermore, risk assessment based on TCS SFA can help 1) to obtain useful information on the likelihood of exposure to uncontrollable adverse effects of " TCS allelopathy " by calculating mass flux of TCS from production to exposure and per capita TCS exposure concentration in the anthroposphere (Huang et al., 2014); 2) to dynamically assess the distribution of potential susceptible population by identifying flow direction and distribution of TCS; 3) to provide more accurate data for secondary pollution risk exposure assessment of TCS. For example, the by-products from TCS biodegradation and photolytic degradation, such as MeTCS and other chlorinated phenols , which may be more resistant to degradation and have higher toxicity than the parent compound (Dann and Hontela, 2011). The amount of MeTCS mainly depends on the amount of TCS mass flows into the environment and degradation routes. "
    [Show abstract] [Hide abstract] ABSTRACT: 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.
    Full-text · Article · Oct 2016
    • "However, TCS could be a potential endocrine disruptor that has been shown to affect development and reproduction in the fish [8]. TCS can easily diffuse through biological membranes and has been detected in maternal milk, urine and plasma with lower concentrations than those found in personal care products containing TCS [8]. Although TCS could represent a potential threat to the developing fetus, so far few studies have evaluated if TCS exposure during gestation can affect the progeny after they are born. "
    [Show abstract] [Hide abstract] ABSTRACT: The objectives of this study were to evaluate the effects of maternal oral exposure to the antibacterial Triclosan (TCS) during gestation and lactation on the metabolic status of the adult offspring and on the expression of main genes controlling the appetite regulatory network. Pregnant rats were fed ad-libitum with ground food + TCS (1 mg/kg) from day 14 of gestation to day 20 of lactation (n=3) or ground food (n=3). After litter reduction, 12 males and 12 females born from the TCS exposed rats (TCS, n=24) or not (Control, n=24) were used to evaluate monthly body weight, food intake, plasma levels of cholesterol, glucose and triglycerides, and the hypothalamic mRNA expression of agouti-related protein (Agrp), neuropeptide Y (Npy) and propiomelanocortin (Pomc). Body weight for rats in the TCS group was 12.5% heavier for males at 4 months (p<0.001) and 19% heavier for females at 8 months (p=0.01). Food intake was significantly higher for rats in the TCS group at 5 months of age (p<0.01). Cholesterol and glucose levels were significantly higher for rats in the TCS group at 8 months (p<0.05). mRNA expression of Npy and Agrp were significantly increased in hypothalami of rats in the TCS group at 2 months for males or 8 months for females (p<0.05). In conclusion, low doses of oral TCS consumption by the pregnant and lactating dam increase the hypothalamic expression of the orexigenic neuropeptides Npy and Agrp in the offspring and alter their metabolic status during adulthood, resembling development of the metabolic syndrome.
    Article · Aug 2016
    • "[41][42][43] To the current scientific knowledge, it remains unclear as to whether TCS has (anti) estrogenic or (anti) androgenic effects. [5] The study of Huang et al. [44] with human cell lines revealed that TCS might have estrogenic activity at lower concentrations and exhibits antiestrogenic activity and/or cytotoxicity at higher concentrations , whereas Raut and Angus [20] and Wang and Tian [21] argue for a dominating agonistic activity of TCS at the estrogen receptor. Although an endocrine-mediated mode of action in the snails could be assumed, supported by the low-effect concentrations and the specificity of both substances regarding modulation of reproductive parameters, the knowledge about the endocrine pathways of P. antipodarum is too limited to come to a final conclusion in this matter. "
    [Show abstract] [Hide abstract] ABSTRACT: In this study, we assessed the chronic effects of the two antimicrobial substances triclocarban (TCC) and triclosan (TCS) on reproduction of a mollusk species by using the reproduction test with the New Zealand mudsnail Potamopyrgus antipodarum. Snails coming from a laboratory culture were exposed for 28 days to nominal concentrations ranging from 0.1 up to 10 µg/L for both chemicals (measured 0.082-8.85 µg TCC/L; 0.068-6.26 µg TCS/L). At the end of the experiment, snails were dissected and embryos in the brood pouch were counted to assess the individualized reproductive success of adult snails. Exposure to TCC resulted in an inverted u-shaped concentration-response relationship, with a stimulation of reproduction at low concentrations followed by an inhibition at higher concentrations. The no observed effect concentration (NOEC) and the lowest observed effect concentration (LOEC) were 0.082 and 0.287 µg/L, respectively. TCS caused significantly increased embryo numbers at all tested concentrations, except in the group of 0.170 µg/L. Therefore, the NOEC for TCS was 0.170 µg/L and the LOEC was 0.660 µg/L. These results indicate that TCC and TCS may cause reproductive effects at environmentally relevant concentrations indicating a potential risk for aquatic organisms in the environment.
    Article · Jul 2016
Show more