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Safety Assessment of Triethanolamine and Triethanolamine-Containing Ingredients as Used in Cosmetics
Abstract
The Cosmetic Ingredient Review Expert Panel assessed the safety of triethanolamine (TEA) and 31 related TEA-containing ingredients as used in cosmetics. The TEA is reported to function as a surfactant or pH adjuster; the related TEA-containing ingredients included in this safety assessment are reported to function as surfactants and hair- or skin-conditioning agents. The exception is TEA-sorbate, which is reported to function as a preservative. The Panel reviewed the available animal and clinical data. Although data were not available for all the ingredients, the panel relied on the information available for TEA in conjunction with previous safety assessments of components of TEA-containing ingredients. These data could be extrapolated to support the safety of all included ingredients. The panel concluded that TEA and related TEA-containing ingredients named in this report are safe as used when formulated to be nonirritating. These ingredients should not be used in cosmetic products in which N-nitroso compounds can be formed.
... Glycerin, responsible for the improvement of skin's smoothness and moisture [65], is used as a humectant in cosmetics at variable concentrations: 10% in face/neck products; 5.0% in body/hand products; 3.3% in moisturizing products [66]. TEA is used in cosmetics as a pH adjuster [67] and used in personal care products at concentrations between 0.0002% and 19% [64,[67][68][69][70]. Methyl paraben, a safe preservative ingredient found in most cosmetics products [38], can be used singly or in combination to enhance the antimicrobial effect, at concentrations below 0.3% [71,72], being normally a non-irritating and non-sensitizing ingredient [71]. Methyl paraben and cetyl alcohol were acquired from Sigma-Aldrich (Munich, Germany). ...
... Glycerin, responsible for the improvement of skin's smoothness and moisture [65], is used as a humectant in cosmetics at variable concentrations: 10% in face/neck products; 5.0% in body/hand products; 3.3% in moisturizing products [66]. TEA is used in cosmetics as a pH adjuster [67] and used in personal care products at concentrations between 0.0002% and 19% [64,[67][68][69][70]. Methyl paraben, a safe preservative ingredient found in most cosmetics products [38], can be used singly or in combination to enhance the antimicrobial effect, at concentrations below 0.3% [71,72], being normally a non-irritating and non-sensitizing ingredient [71]. ...
Driven by the customers’ growing awareness of environmental issues, the production of topical formulations based on sustainable ingredients is receiving widespread attention from researchers and the industry. Although numerous sustainable ingredients (natural, organic, or green chemistry-derived compounds) have been investigated, there is a lack of comparative studies between conventional ingredients and sustainable alternatives. In this study, olive oil (30 wt.%) and α-tocopherol (2.5 wt.%) containing oil-in-water (O/W) emulsions stabilized with the bacterial fucose-rich polysaccharide FucoPol were formulated envisaging their validation as cosmetic creams. After formula composition design by Response Surface Methodology (RSM), the optimized FucoPol-based emulsion was prepared with 1.5 wt.% FucoPol, 1.5 wt.% cetyl alcohol, and 3.0 wt.% glycerin. The resulting emulsions had an apparent viscosity of 8.72 Pa.s (measured at a shear rate 2.3 s−1) and droplet size and zeta potential values of 6.12 µm and −97.9 mV, respectively, which are within the values reported for cosmetic emulsified formulations. The optimized formulation displayed the desired criterium of a thin emulsion system, possessing the physicochemical properties and the stability comparable to those of commercially available products used in cosmeceutical applications.
... Despite their common use, many amino alcohols have major drawbacks. TEA, for example, has been linked to allergic contact dermatitis (Bruze et al. 1995;Chu and Sun 2001), seawater ecotoxicity (Libralato et al. 2010), and carcinogenic activity (Fiume et al. 2013). In addition, it is listed on the EU "Control List of Dual-Use Items in Annex I to Regulation (EC) No 428/2009" which entails further regulation and higher cost. ...
We present alkali salts of amino acids as functional, non-toxic, non-hazardous, non-volatile, chemically stable, and cheap alkaline additives for common acidic corrosion inhibitors. The resulting mixtures have been evaluated for Co, Ni, and Cu leaching and were analyzed by chip filter assay, potentiodynamic polarization measurements, electrochemical impedance measurements, and gravimetry for corrosion protection of iron and steel in aqueous environment at slightly alkaline pH. Leaching of Co and Ni was found to depend on the corresponding complex stabilities. Taurine (Tau) as well as aminohexanoic acid (AHX) leads to low leaching of Co and Ni. Particularly AHX is an attractive low leaching additive leading to lower Co and Ni concentrations in solution than currently used amino alcohols. Glu and Tau were found to synergistically interact with several acidic corrosion inhibitors of the carboxylic acid and the phosphonic acid type. Tau had a particularly positive impact on the protective properties of carboxyphosphonic acids. Glu had also a positive effect on the anti-corrosive properties of several acidic corrosion inhibitors and served as an anti-scalant. Alkali salts of Glu and Tau might thus serve as commercially and ecologically attractive substitutes for current alkaline additives to acidic corrosion inhibitors.
... In order to reach this endpoint, percentages of NaOH and TEA in the whole formulation are: 0.5 % w/v and 0.275 % v/v, respectively. These amounts do not exceed the percentages allowed in topical formulations: 10% for NaOH 342,343 and 5% for TEA 344 . ...
From acute wounds to diseases -such as psoriasis or dermatitis- skin is submitted to numerous biological and physio-pathological situations where prooxidant and antioxidant reactions must be finely controlled. Particularly, the excess of reactive oxygen species (ROS), which is often related to inflammatory processes. Natural exogenous antioxidant molecules -like curcumin- represent pertinent candidates to favour this prooxidant-antioxidant balance; especially due to their capacity to control the toxicity of radicals and to activate cytoprotective signalling pathways in dermal cells.However, due to their hydrophobic nature, the formulation of such compounds remains a challenge. It is thus necessary, especially with curcumin, to develop strategies able to deliver it at the site of action, while preserving its antioxidant properties and with adjustment of its capacity of penetration into the dermis through an appropriate application to the skin surface.The overall objective of this work was on one hand, to develop a multiscale composite delivery platform, based on a hydrogel matrix containing a curcumin-loaded nanoparticulated reservoir, On the other hand, to evaluate it in order to explore its potential for topical dermal uses.First this work has been focused on the design, preparation, as well as physicochemical and biological characterization of curcumin-loaded Nanostructured Lipid Carriers (CUR-NLCs). Second, the incorporation of these curcumin reservoirs in a carbomer hydrogel have been studied. The applicability for a topical dermal use was studied at the cell level by assessing CUR-NLCs impact on migration/proliferation as well as their influence in cells undergoing oxidative stress. Moreover, CUR-NLCs incorporated in the hydrogel (CUR-NLCs/gel) were evaluated in terms of their ability to control curcumin penetration into synthetic membranes mimicking the human skin.The main results show that it is possible to obtain, with an encapsulation efficiency of 85%, stable and reproducible NLCs formulation mostly composed of negatively charged nanoparticles of two size populations (P1, 70-85 nm and P2, 280-360 nm). These NLCs are able to preserve curcumin antioxidant properties. The developed carriers were found to reduce the proliferation/migration of both human fibroblasts and keratinocytes cells in vitro. Moreover, they did not affect their metabolic activity even when assessed in an in vitro oxidative stress model (for CUR concentrations up to 10 μM). CUR-NLCs are less likely to cross synthetic membranes mimicking intact human skin, but they could contribute to curcumin accumulation into them. This effect is modulated by their incorporation into the hydrogel.These results showed the feasibility of using CUR-NLCs/gel as a platform for curcumin delivery to the skin. The fact that CUR-NLCs do not affect cellular viability ([CUR] below or equal to 10 μM), even during oxidative stress conditions, makes them good candidates for the development of topical treatments where protection from oxidative stress and a controlled cell migration are needed without compromising metabolic activity.
... Journal Pre-proof h exposure [168]. However, other works have ranked the chemical as non-toxic to all taxa [167,169,170]. Results in Figure 7 also show that cetrimonium bromide and polymeric biguanide hydrochloride are highly toxic to algae with E(L)C50s of 4.00 mg/L and 19.0 µg/L, respectively [171]. ...
In response to the novel coronavirus referred to as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) – a virus that causes COVID-19 disease has led to wide use of sanitizers and disinfectants. This, in turn, triggered concerns on their potential deleterious effects to human health and the environment due to numerous chemicals incorporated in both product categories. Here, the current state of science regarding the occurrence and ecological effects of different classes of chemicals in these products (e.g., ultraviolent filters, fragrances, etc.) are summarized in different natural (e.g., rivers) and engineered (e.g., wastewater treatment plants) systems. Data collected in the literature suggests chemicals incorporated in sanitizers and disinfectants are present in the environment, and a large portion are toxic to fish, algae, and daphnia. Using the risk quotient approach based on occurrence data, we found eight chemicals that posed the highest risk to aquatic organisms in freshwater systems were benzalkonium chloride, 4-chloro-m-cresol, sodium ortho phenyl phenate, hydrogen peroxide, 1, 2-propanediol, 4-Methyl-benzilidine-camphor, ethylhexyl methoxy cinnamate, and octocrylene. Considering limited occurrence and effects information for most chemicals, further studies on environmental monitoring and potential consequences of long-term exposure in aquatic ecosystems are recommended.
... They are used to obtain creams, shampoos, washing preparations and others. They are also often used as gelling agents in polymer preparations [34][35][36]. In an earlier research, Musial and Kubis demonstrated another interesting feature of alcoholamines. ...
Due to its high instability and rapid degradation under adverse conditions, tetracycline hydrochloride (TC) can cause difficulties in the development of an effective but stable formulation for the topical treatment of acne. The aim of the following work was to propose a hydrogel formulation that would ensure the stability of the antibiotic contained in it. Additionally, an important property of the prepared formulations was the activity of the alcoholamines contained in them against the components of the model sebum. This feature may help effectively cleanse the hair follicles in the accumulated sebum layer. A series of formulations with varying proportions of anionic polymer and alcoholamine and containing different polymers have been developed. The stability of tetracycline hydrochloride contained in the hydrogels was evaluated for 28 days by HPLC analysis. Formulations containing a large excess of TRIS alcoholamine led to the rapid degradation of TC from an initial concentration of about 10 µg/mL to about 1 µg/mL after 28 days. At the same time, these formulations showed the highest activity against artificial sebum components. Thanks to appropriately selected proportions of the components, it was possible to develop a formulation that assured the stability of tetracycline for ca. one month, while maintaining formulation activity against the components of model sebum.
... After addition of carbopol, about 0.5 ml of 5% triethanolamine was added for crosslinking carbopol gel. Triethanolamine neutralizes carboxy groups such as carbomer to form a stable polymer structure, so as to achieve the application effect of thickening and moisturizing [27]. Final pH of the SLN formulation was about 4.5. ...
Hot melt extrusion (HME) has been used for the formulation of topical solid lipid nanoparticle (SLN) gel without using any other size reduction technique including high pressure homogenization or sonication. SLN formulation solely using HME has not been applied to other drugs except IBU. Therefore, the purpose of the present study was to formulate FLB SLN solely using HME technique and evaluate the SLN formulation in inflammation animal model. Stable 0.5% w/v FLB SLN gel with particle size < 250 nm, PI < 0.3 and EE of > 98% was prepared. Differential scanning calorimetry (DSC) thermogram showed that the drug was converted to amorphous form in the HME process. Additionally, rheological studies demonstrated that FLB SLN gel and marketed FLB gel showed shear thinning property. FLB SLN formulation showed significantly (p < 0.05) higher peak force required to spread the formulation as compared to marketed FLB formulation. Stability studies showed that FLB SLN gel was stable for a month at room temperature and 2–4°C. Moreover, in vitro permeation test (IVPT) and ex vivo skin deposition study results revealed that FLB SLN gel showed significant (p < 0.05) increase in drug deposition in dermal layer and drug permeation as compared to control marketed formulation. Further, in vivo anti-inflammatory study showed equivalent inhibition of rat paw edema using 0.5% w/v FLB SLN gel which has 10 times less strength compared to control formulation. Overall, FLB SLN formulation was successfully manufactured solely using HME technique which resulted in enhanced the skin permeation of FLB and superior anti-inflammatory activity.
In this study, the physicochemical characteristics, bioactive properties, and sensorial evaluation of a O/W cosmetic formulation containing FucoPol, a fucose-containing bacterial polysaccharide, were assessed. The stability of the FucoPol-based cream, named F-cream, was demonstrated over a period of 2 months at different temperatures (4, 20 and 30 °C), during which it maintained the organoleptic characteristics and pH (5.88-6.19), with minimal variations on the apparent viscosity. Furthermore, no breaking mechanisms occurred upon centrifuging the samples (accelerated stability test) kept at 4 °C and at 30 °C for 60 days. The F-cream presented a shear-thinning and solid-liquid behavior consistent with its envisaged use for topical applications, proving to be a suitable candidate for an anti-aging application due to its antioxidant capacity and effective photoprotection, maintaining cellular preservation. Moreover, the formulation was proven non-cytotoxic for HaCaT cells at concentrations between 0.78 and 12.5 mg/mL, promoting HFFF2 cell migration (46-70 % of wound closure) at a concentration of 2.5 mg/mL, and HaCaT cell migration at a concentration of 10 mg/mL (95-98 % of wound closure). Upon application over the skin, the F-cream provided a hydration and softness with desired spreadability with no residues after application. These findings show that FucoPol has good potential to be used as a functional and/or active ingredient in cosmetic formulations, forming an emulsified cream with appealing sensorial properties that can act as a moisturizer with photoprotection, antioxidant, and regeneration properties.
Cyclodextrin metal-organic frameworks (CD-MOF) are a class of biocompatible MOF with a great potential in drug delivery applications. Original CD-MOF crystals are fragile and large (0.2-1 mm), which are less useful in pharmaceutical applications. Cetyltrimethylammonium bromide and long chain poly(ethylene) glycol, used in size modulation to produce nanosized CD-MOF can compromise the biocompatibility, and physiochemical properties of CD-MOF as their complete removal from frameworks is difficult. To avoid the use of above-mentioned modulators, herein, we demonstrate the synthesis of nanosized CD-MOF using triethylamine (TEA) as a modulator to reduce their size to ~254 nm. The MOF characteristics such as crystal and chemical structure remain unaffected and the surface area of CD-MOF synthesised with TEA is measured 1075.5 m2/g, almost 50 % higher than those of synthesised using bulky modulators. The improved CD-MOF architecture utilized for the in-situ synthesis of silver nanoparticles resulted in enhanced antimicrobial efficacy tested against Staphylococcus aureus and Escherichia coli bacteria and Candida albicans fungus. And minimum inhibitory concentration (MIC) is recorded in the range of 31-15 μg/mL. Overall, the structural improvement in CD-MOF supported with thorough comparative investigations and enhanced antimicrobial efficacy could be very helpful in further establishing them in biomedicine field.
Recently, we described the use of a chemical matrix for landing and preserving the cations of protein-protein complexes within a mass spectrometer (MS) instrument. By use of a glycerol-landing matrix, we used negative stain transmission electron microscopy (TEM) to obtain a three-dimensional (3D) reconstruction of landed GroEL complexes. Here, we investigate the utilities of other chemical matrices for their abilities to land, preserve, and allow for direct imaging of these cationic particles using TEM. We report here that poly(propylene) glycol (PPG) offers superior performance over glycerol for matrix landing. We demonstrated the utility of the PPG matrix landing using three protein-protein complexes─GroEL, the 20S proteasome core particle, and β-galactosidase─and obtained a 3D reconstruction of each complex from matrix-landed particles. These structures have no detectable differences from the structures obtained using conventional preparation methods, suggesting the structures are well preserved at least to the resolution limit of the reconstructions (∼20 Å). We conclude that matrix landing offers a direct approach to couple native MS with TEM for protein structure determination.
Amino alcohols like triethanolamine (TEA), 2‐amino‐2‐methylpropanol (AMP), or 1‐aminopropan‐2‐ol (MIPA) are common ingredients in industrial metalworking fluids. They are used in large quantities as alkaline additives for the neutralization of acidic corrosion inhibitors and are typical industrial products from the oil‐based value chain. The criteria for the selection of these additives have changed in the last decades and are nowadays not only performance‐driven but influenced by ecological considerations, toxicity, and regulatory standards. In this study, we evaluate the sugar derivative N,N‐diethylglucamine (DEGA) for use as a functional, nonvolatile, chemically stable, and cheap alkaline additive for common acidic corrosion inhibitors. Electrochemical analyses confirm anticorrosive properties of DEGA comparable to the gold standard TEA for iron and steel in an aqueous environment at a slightly alkaline pH. In addition, DEGA leads to extremely low levels of Co, Ni, and Cu leaching and can thus also serve as a nonvolatile substitute for currently used low‐leaching additives such as AMP and MIPA. The diethylamino‐motif is a sweet spot among different glucamine derivatives tested because it combines easy synthetic accessibility with good water solubility and low‐leaching properties. Besides this, DEGA can be prepared in one step from glucose and diethylamine, both derived from renewable resources. This paper describes the scalable synthesis of N,N‐diethylglucamine (DEGA) from glucose and diethylamine in one step and its evaluation as an alkaline additive to common acidic corrosion inhibitors. Electrochemical measurements and flame atomic absorption spectroscopy revealed good anticorrosive properties and low leaching of important alloying metals such as Co, Ni, and Cu.
TEA Stearate is the triethanolamine salt of stearic acid used as a surfactant-cleansing agent and a surfactant-emulsifying agent in a wide variety of cosmetic formulations. Published data on TEA Stearate as an individual ingredient were not available, but data on its two components, TEA and stearic acid, were previously reviewed and considered adequate to evaluate the safety of TEA Stearate. Information from the earlier reports was summarized in this report and updated with more recent data on TEA. These data were consistent with the conclusion that TEA is safe for use in rinse- off cosmetic formulations, that its concentration should not exceed 5% in leave-on formulations, and that in no case should it be used in products containing N-nitrosating agents. Stearic Acid was found safe as used. Because the TEA salt of stearic acid is not expected to exhibit any toxic effects not seen with the separate moities, these conclusions, including the concentration limit for TEA, are considered applicable to TEA Stearate, once adjusted for the appropriate molecular weights. Therefore, it is concluded that TEA Stearate is safe as used in cosmetic formulations designed for discontinuous, brief use followed by thorough rinsing; that it is safe in concentrations not to exceed 15% in formulations intended for prolonged contact with the skin; and that it should not be used in products under conditions resulting in N-nitrosation reactions.
Dioctyl Sodium Sulfosuccinate is an anionic surfactant used in a wide variety of cosmetic formulations. In September 1994, the Cosmetic Ingredient Review (CIR) Expert Panel evaluated the ingredient to be safe up to 0.42% in cosmetic formulations. Since that time, CIR received a petition to re-open the safety assessment based on new clinical data. This amendment is a compilation of data contained in the original plus the data received in the petition; the latter appear at the end of this document. Studies conducted in the 1940's indicate that the oral LD50 in rats can be as low as 1.9 g/kg. Short-term subchronic and chronic animal studies of the same vintage found little toxicity at levels around 1% of the LD50 level. Inhalation studies likewise had few findings. Dioctyl Sodium Sulfosuccinate was minimally irritating to intact animal skin, but moderate to severely irritating to abraded skin. A concentration of 25% was a severe ocular irritant, but 10% produced little or no irritation. Mutagenesis tests were negative. A repeated insult patch test (RIPT) in 110 individuals produced no sensitization at a concentration of 5%. Erythema was noted during induction in a number of subjects at concentrations ≤5%. The CIR Expert Panel recognized that surfactants such as Dioctyl Sodium Sulfosuccinate would likely produce irritation under the conditions of a RIPT. The Panel cautioned that as the ingredient is a cumulative irritant, care should be taken to avoid irritancy in formulations intended for prolonged contact with the skin. The Panel concluded that Dioctyl Sodium Sulfosuccinate is safe for use in cosmetics.
This report provides a review of the safety of Glycolic Acid, Ammonium, Calcium, Potassium, and Sodium Glycolates, Methyl, Ethyl, Propyl, and Butyl Glycolates, Lactic Acid, Ammonium, Calcium, Potassium, Sodium, and TEA-Lactates, and Lauryl, Myristyl, and Cetyl Lactates. These ingredients belong to a group known as alpha-hydroxy acids (AHAs). Products containing these ingredients may be for consumer use, salon use, or medical use. This report does not address the medical use. In consumer and salon use, AHAs can function as mild exfoliants, but are also used as pH adjusters and skin-conditioning agents. AHAs are absorbed by the skin; the lower the pH, the greater the absorption. Metabolism and distribution studies show expected pathways and distribution. Consistent with these data, acute oral animal studies show oxalate-induced renal calculi, an increase in renal oxalate, and nephrotoxic effects. No systemic effects in animals were seen with dermal application, but irritation at the sight of application was produced. While many animal studies were performed to evaluate AHA-induced skin irritation, it was common for either the AHA concentration or the pH of the formulation to be omitted, limiting the usefulness of the data. Clinical testing using AHA formulations of known concentration and pH was done to address the issue of skin irritation as a function of concentration and pH. Skin irritation increased with AHA concentration at a given pH. Skin irritation increased when the pH of a given AHA concentration was lowered. Repeat insult patch tests using lotions and creams containing up to 10% Glycolic or Lactic Acid were negative. Glycolic Acid at concentrations up to 10% was not comedogenic and Lactic Acid at the same concentrations did not cause immediate urticarial reactions. Glycolic Acid was found to be nonirritating to minimally irritating in animal ocular tests, while Lactic Acid was found to be nonirritating to moderately irritating. In vitro testing to predict ocular irritation suggested Glycolic Acid would be a minimal to moderate-severe ocular irritant, and that Lactic Acid would be a minimal to moderate ocular irritant. Developmental and maternal toxicity were reported in rats dosed by gavage at the highest dose level used in a study that exposed the animals on days 7-21 of gestation. No developmental toxicity was reported at levels that were not maternally toxic. AHAs were almost uniformly negative in genotoxicity tests and were not carcinogenic in rabbits or rats. Clinical reports suggested that AHAs would enhance the penetration of hydroquinone and lidocaine. Animal and clinical tests were done to further evaluate the potential ofAHAs to enhance the skin penetration of other chemical agents. Pretreatment of guinea pig skin with Glycolic Acid did not affect the absorption of hydroquinone or musk xylol. Clinical tests results indicated no increase in penetration of hydrocortisone or glycerin with Glycolic Acid pretreatment. Because AHAs can act to remove a portion of the stratum corneum, concern was expressed about the potential that pretreatment with AHAs could increase skin damage produced by UV radiation. Clinical testing was done to determine the number of sunburn cells (cells damaged by UV radiation that show distinct morphologic changes) produced by 1 MED of UV radiation in skin pretreated with AHAs. A statistically significant increase in the number of sunburn cells was seen in skin pretreated with AHAs compared to controls. These increases, however, were less than those seen when the UV dose was increased from 1 MED to 1.56 MED. The increase in UV radiation damage associated with AHA pretreatment, therefore, was of such a magnitude that it is easily conceivable that aspects of product formulation could eliminate the effect. Based on the available information included in this report, the CIR Expert Panel concluded that Glycolic and Lactic Acid, their common salts and their simple esters, are safe for use in cosmetic products at concentrations ≤10%, at final formulation pH≥3.5, when formulated to avoid increasing sun sensitivity or when directions for use include the daily use of sun protection. These ingredients are safe for use in salon products at concentrations ≤30%, at final formulation pH ≥3.0, in products designed for brief, discontinuous use followed by thorough rinsing from the skin, when applied by trained professionals, and when application is accompanied by directions for the daily use of sun protection.
The mouse peripheral blood micronucleus (MN) test was performed on samples collected from 20 short-term, 67 subchronic, and 5 chronic toxicity and carcinogenicity studies conducted by the National Toxicology Program (NTP). Data are presented for studies not previously published. Aspects of protocol that distinguish this test from conventional short-term bone marrow MN tests are duration of exposure, and absence of repeat tests and concurrent positive controls. Furthermore, in contrast to short-term bone marrow MN tests where scoring is limited to polychromatic erythrocytes (PCE), longer term studies using peripheral blood may evaluate MN in both, or either, the normochromatic (NCE) or PCE populations. The incidence of MN-PCE provides an index of damage induced within 72 hr of sampling, whereas the incidence of MN in the NCE population at steady state provides an index of average damage during the 30-day period preceding sampling. The mouse peripheral blood MN test has been proposed as a useful adjunct to rodent toxicity tests and has been effectively incorporated as a routine part of overall toxicity testing by the NTP. Data derived from peripheral blood MN analyses of dosed animals provide a useful indication of the in vivo potential for induced genetic damage and supply an important piece of evidence to be considered in the overall assessment of toxicity and health risk of a particular chemical. Although results indicate that the test has low sensitivity for prediction of carcinogenicity, a convincingly positive result in this assay appears to be highly predictive of rodent carcinogenicity. Environ. Mol. Mutagen. 36:163–194, 2000 © 2000 Wiley-Liss, Inc.