A role for surface reactivity in TiO2 and quartz-related nanoparticle pulmonary toxicity

A variety of pulmonary hazard studies in rats have demonstrated that exposures to ultrafine or nanoparticles (generally defined as particles in the size range < 100 nm) produce more intensive inflammatory responses when compared with bulk-sized particle-types of similar chemical composition. However, this common perception of greater nanoparticle toxicity is based on a limited number of studies, conducted primarily with titanium dioxide and carbon black particle-types. Apart from variables such as particle size and surface area, it is conceivable that several additional physicochemical particle characteristics could play more significant roles in facilitating the development of nanoparticle-related toxicity; particularly when considering particle surface-cell interactions. These include but are not limited to: (i) Surface reactivity of particle-types; (ii) surface coatings; (iii) aggregation/disaggregation potential; and (iv) the method of nanoparticle synthesis. We present results of pulmonary bioassay hazard/safety studies with quartz particles of varying sizes/surface areas. These demonstrated that intratracheal instillation exposures to fine-sized, Min-U-Sil quartz particles (0.5 µm [particle size] – 5 m²/g [surface area]) produced (persistent) enhanced pulmonary toxicity (inflammation, cytotoxicity, cell proliferation and/or histopathology) in rats when compared to nanoscale quartz particles (50 nm–31 m²/g), but not when compared to smaller nanoscale quartz sizes (e.g., 12 nm–91 m²/g). The toxicity results correlated with red blood cell hemolytic potency as a measure of particle surface reactivity. In a second pulmonary bioassay study in rats, pulmonary hazard effects were measured following exposures to three different ultrafine (nano) TiO₂ particle-types, each with similar particle size distributions. The various TiO₂ particles differed in their crystal structures and surface reactivity endpoints as measured by the Vitamin C yellowing assay. Moreover, the surface activity characteristics correlated with potency of hazard biomarkers as described above, in these dose/response, time-course studies. It is concluded that particle surface reactivity, rather than particle size/surface area endpoints correlated best with lung inflammatory potency following exposures to particles.     

Rationale of genotoxicity testing of nanomaterials: Regulatory requirements and appropriateness of available OECD test guidelines

Abstract

The development of an environmental health and safety risk management system for nanoscale particle-types requires a base set of hazard data. Accurate determination of health and environmental risks of nanomaterials is a function of the integration of hazard and exposure datasets. Recently, a nanoparticle risk assessment strategy was promulgated and the components are described in a document entitled “Nanorisk framework” (www.nanoriskframework.com). A major component of the hazard evaluation includes a proposed minimum base set of toxicity studies. Included in the suggested studies were substantial particle characterization, a variety of acute hazard and environmental tests, concomitant with screening-type genotoxicity studies. The implementation of well-accepted genotoxicity assays for testing nanomaterials remains a controversial issue. This is because many of these genotoxicity tests were designed for screening general macroparticle chemicals and might not be suitable for the screening of nanomaterials (even of the same compositional material). Furthermore, no nanoparticle-type positive controls have been established or universally accepted for these tests. Although it is the comparative results of the test material vs. the negative or vehicle control that forms the basis for interpreting the results and potency of test materials in genetic toxicology assays, the lack of a nanoparticle-type positive control questions the suitability of the tests to identify nanomaterials with genotoxic properties. It is also not possible to establish historical positive control ranges that would confirm the sensitivity of the tests. Although several genetic toxicology tests have been validated for chemicals according to the Organisation for Economic Co-operation and Development (OECD) test guidelines, the relevance of these assays for nanoparticulate materials remains to be determined. In an attempt to remedy this issue, the OECD has established current projects designed to evaluate the relevance and reproducibility of safety hazard tests for representative nanomaterials, including genotoxicity assays (i.e., Steering Group 3 – Safety Testing of Representative Nanomaterials). In this article, we discuss our past approaches and experience in conducting genotoxicity assays (1) for a newly developed ultrafine TiO₂ particle-type; and (2) in a recent inhalation study, evaluating micronucleus formation in rat erythrocytes following exposures to engineered amorphous nanosilica particles. It seems clear that the development of standardized approaches will be necessary in order to determine whether exposures to specific nanoparticle-types are associated with genotoxic events. The appropriateness of available genotoxicity test systems for nanomaterials requires confirmation and standardization. Accordingly, it seems reasonable to conclude that any specific regulatory testing requirements for nanoparticles would be premature at this time.     

Tiered toxicity testing: Evaluation of toxicity-based decision triggers for human health hazard characterization

A set of biologically-based toxicity testing decision triggers was developed and analyzed within a tiered testing and decision-making framework for evaluating potential human health hazards and risks associated with chemical exposures. The proposed three-tiered toxicity testing approach starts from a base set of toxicity studies (acute toxicity, in vitro genetic toxicity, in vitro cytogenetics, repeat dose/subchronic toxicity, developmental toxicity, reproductive toxicity) and then uses the toxicity triggers to identify which specific additional tests are needed to adequately characterize a substance’s hazard potential. The toxicity triggers were initially evaluated using published information for eight chemicals, representing diverse classes. A retrospective validation study was then conducted using seven chemicals which had completed the USEPA’s Voluntary Children’s Chemical Evaluation Program (VCCEP). The toxicity triggers were shown to identify appropriate higher tier tests and to be reasonably predictive of the results expected in higher tiered tests. Employing these toxicity triggers within a tiered testing framework could lead to a reduction in the number of laboratory animals without diminishing the degree of scientific certainty necessary for hazard evaluations. The toxicity triggers appear to be suitable for identifying which specific endpoints and tests warrant further evaluation, and which do not, and for documenting the scientific basis for such decisions.     

Acute toxicity testing of chemicals—Opportunities to avoid redundant testing and use alternative approaches

Assessment of the acute systemic oral, dermal, and inhalation toxicities, skin and eye irritancy, and skin sensitisation potential of chemicals is required under regulatory schemes worldwide. In vivo studies conducted to assess these endpoints can sometimes be associated with substantial adverse effects in the test animals, and their use should always be scientifically justified. It has been argued that while information obtained from such acute tests provides data needed to meet classification and labelling regulations, it is of limited value for hazard and risk assessments. Inconsistent application of in vitro replacements, protocol requirements across regions, and bridging principles also contribute to unnecessary and redundant animal testing. Assessment of data from acute oral and dermal toxicity testing demonstrates that acute dermal testing rarely provides value for hazard assessment purposes when an acute oral study has been conducted. Options to waive requirements for acute oral and inhalation toxicity testing should be employed to avoid unnecessary in vivo studies. In vitro irritation models should receive wider adoption and be used to meet regulatory needs. Global requirements for sensitisation testing need continued harmonisation for both substance and mixture assessments. This paper highlights where alternative approaches or elimination of tests can reduce and refine animal use for acute toxicity requirements.     

Toxicity of different industrial effluents in Taiwan: a comparison of the sensitivity of Daphnia similis and Microtox

Industrial effluents are known to exhibit toxicity toward different aquatic organisms. In Taiwan management of these discharges still relies on chemical and physical and physical characteristics of water, although various standard method for assessing aquatic toxicity have been proposed by the Taiwan Environmental Protection Administration. In this study we examined the toxicity and compared the sensitivity of different types of industrial effluents using two proposed toxicity tests: the Daphnia similis acute toxicity test and the Microtox acute assay (Vibrio fischeri). Results showed that electroplating effluents were the most toxic of all the effluents tested, followed by acrylonitrile manufacturing, pulp/paper, and tannery effluents. The EC50 of an electroplating effluent for D. similis and V. fischeri (15 min) was as low as, respectively, 2.9% and 3.9% of the whole effluent. The other effluents were not acutely toxic to either organism tested. However, the tests exhibited different sensitivity toward various discharges. Only the electroplating and acrylonitrile manufacturing effluents had effects on both organisms. These results indicate the importance of the incorporation of aquatic toxicity tests into the management scheme for treated wastewaters.     

Studies on the environmental fate,ecotoxicology and toxicology of 2-methyl 1,3-propanediol

2-methyl 1,3-propandiol (MPD) is a low molecular weight, colorless glycol used in polymer and coating applications. The log Kow of −0.6 suggests partitioning to aqueous phases with a low concern for possible bioaccumulation. MPD was found to be inherently biodegradable. Ecotoxicological results in several aquatic and terrestrial species found no significant hazard potential. MPD is rapidly absorbed via the oral and dermal routes, metabolized to 3-hydroxybutyrate, and excreted in urine with a half-life of 3.6 h. Acute toxicity testing found low toxicity via all routes. Barely perceptible skin irritation was observed in human volunteers, whereas there was no evidence of irritation in rabbits. Skin sensitization in Guinea pigs was negative. Human skin patch results indicated minimal response in about 1% of individuals. There was no evidence of mutagenicity using bacterial and mammalian test systems. A 90-day oral study in rats found no adverse effects at any dose. Three developmental toxicity studies in rats and rabbits, found no treatment-related maternal toxicity, fetal toxicity or malformations. A two-generation reproduction study in rats found no consistent treatment-related adverse effects on reproduction in either generation. No carcinogenicity studies with MPD were identified. MPD presents a low degree of toxicological and ecotoxicological or environmental hazard.     

How to measure hazards/risks following exposures to nanoscale or pigment-grade titanium dioxide particles

Due to its multifunctional applications, titanium dioxide particles have widespread use in commerce. The particle-types function as sources of pigment color, in food products, anti-bacterial components, ultraviolet radiation scavengers, catalysts, as well as in cosmetics. Because of its inherent properties in a diverse number of products, exposures may occur via any of the major point-of-entry routes, i.e., inhalation, oral or dermal. Although the majority of TiO₂ applications are known to exist in the pigment-grade form, nanoscale forms of TiO₂ are also common components in several products. This brief review is designed to identify relevant toxicology and risk-related issues which inform health effects assessments on the various forms of titanium dioxide particles. While there has been an abundance of hazard data generated on titanium dioxide particulates, many of the published reports have limited informational value for assessing health effects due, in large part, to shortcomings in experimental design issues, such as: (1) inadequate material characterization of test samples; (2) questionable relevance of experimental systems employed to simulate human exposures; (3) applications of generally high doses, exclusive focus on acute toxicity endpoints, and a lack of reference benchmark control materials, to afford interpretation of measured results; and/or (4) failure to recognize fundamental differences between hazard and risk concepts. Accordingly, a number of important toxicology issues are identified and integrated herein to provide a more comprehensive assessment of the health risks of different forms of pigment-grade and nanoscale titanium dioxide particles. It is important to note that particle-types of different TiO₂ compositions may have variable toxicity potencies, depending upon crystal structure, particle size, particle surface characteristics and surface coatings. In order to develop a more robust health risk evaluation of TiO₂ particle exposures, this review focuses on the following issues:

(1)

Introduction to TiO₂ particle chemistry/functionality and importance of robust material characterization of test samples;     

Dermal toxicity,eye and dermal irritation and skin sensitization evaluation of a new formulation of Bacillus thuringiensis var israelensis SH-14

Bacillus thuringiensis (Bt) is the best known and most widely used of all pesticidal microbes. The aim of this study was to assess the toxicity of a new formulation of Bacillus thuringiensis var israelensis SH-14 in rats through acute dermal toxicity, dermal and eye irritation experiments. The acute dermal toxicity and dermal and eye irritation studies were performed using rabbits according to the United States Environmental Protection Agency guidelines 885.3100, 870.2500 and 870.2500, respectively. The skin sensitization study was carried out in accordance to the EPA OPPTS 870.2600 using guinea pigs. There was no mortality and no evidence of treatment-related toxicity in acute dermal toxicity test. No dermal responses, including erythema/eschar or edema, were found in rabbits treated with the new formulation of Bti SH-14. Minimum response was observed after eye application of test substance. No skin sensitization reactions were observed after the challenge with the new formulation of Bti SH-14 in the Bti SH-14-treated guinea pigs. In summary, the present study demonstrated that the new formulation of Bti SH-14 is not acutely toxic via dermal route, has low eye irritation and would not cause dermal irritation or hypersensitivity to tested animals.     

Comparative pulmonary toxicity inhalation and instillation studies with different TiO2 particle formulations: impact of surface treatments on particle toxicity.

Most pigment-grade titanium dioxide (TiO(2)) samples that have been tested in pulmonary toxicity tests have been of a generic variety-i.e., generally either uncoated particles or TiO(2) particles containing slightly hydrophilic surface treatments/coatings (i.e., base TiO(2)). The objectives of these studies were to assess in rats, the pulmonary toxicity of inhaled or intratracheally instilled TiO(2) particle formulations with various surface treatments, ranging from 0-6% alumina (Al(2)O(3)) or alumina and 0-11% amorphous silica (SiO(2)). The pulmonary effects induced by TiO(2) particles with different surface treatments were compared to reference base TiO(2) particles and controls. In the first study, groups of rats were exposed to high exposure (dose) concentrations of TiO(2) particle formulations for 4 weeks at aerosol concentrations ranging from 1130-1300 mg/m(3) and lung tissues were evaluated by histopathology immediately after exposure, as well as at 2 weeks and 3, 6, and 12 months postexposure. In the second study, groups of rats were intratracheally instilled with nearly identical TiO(2) particle formulations (when compared to the inhalation study) at doses of 2 and 10 mg/kg. Subsequently, the lungs of saline-instilled and TiO(2)-exposed rats were assessed using both bronchoalveolar (BAL) biomarkers and by histopathology/cell proliferation assessment of lung tissues at 24 h, 1 week, 1 and 3 months postexposure. The results from these studies demonstrated that for both inhalation and instillation, only the TiO(2) particle formulations with the largest components of both alumina and amorphous silica surface treatments produced mildly adverse pulmonary effects when compared to the base reference control particles. In summary, two major conclusions can be drawn from these studies: (1) surface treatments can influence the toxicity of TiO(2) particles in the lung; and (2) the intratracheal instillation-derived, pulmonary bioassay studies represent an effective preliminary screening tool for inhalation studies with the identical particle-types used in this study.     

Triethylene glycol HO(CH2CH2O)3H

TEG is a liquid higher glycol of very low vapor pressure with uses that are primarily industrial. It has a very low order of acute toxicity by i.v., i.p., peroral, percutaneous and inhalation (vapor and aerosol) routes of exposure. It does not produce primary skin irritation. Acute eye contact with the liquid causes mild local transient irritation (conjunctival hyperemia and slight chemosis) but does not induce corneal injury. Animal maximization and human volunteer repeated insult patch tests studies have shown that TEG does not cause skin sensitization. A study with Swiss-Webster mice demonstrated that TEG aerosol has properties of a peripheral chemosensory irritant material and caused a depression of breathing rate with an RD(50) of 5140 mg m(-3). Continuous subchronic peroral dosing of TEG in the diet of rats did not produce any systemic cumulative or long-term toxicity. The effects seen were dose-related increased relative kidney weight, increased urine volume and decreased urine pH, probably a result of the renal excretion of TEG and metabolites following the absorption of large doses of TEG. There was also decreased hemoglobin concentration, decreased hematocrit and increased mean corpuscular volume, probably due to hemodilution following absorption of TEG. The NOAEL was 20 000 ppm TEG in diet. Short-term repeated aerosol exposure studies in the rat demonstrated that, by nose-only exposure, the threshold for effects by respiratory tract exposure was 1036 mg m(-3). Neither high dosage acute nor repeated exposures to TEG produce hepatorenal injury characteristic of that caused by the lower glycol homologues. Elimination studies with acute peroral doses of TEG given to rats and rabbits showed high recoveries (91-98% over 5 days), with the major fraction appearing in urine (84-94%) and only 1% as CO(2). TEG in urine is present in unchanged and oxidized forms, but only negligible amounts as oxalic acid. Developmental toxicity studies with undiluted TEG given by gavage produced maternal toxicity in rats (body weight, food consumption, water consumption, and relative kidney weight) with a NOEL of 1126 mg kg(-1) day(-1), and mice (relative kidney weight) with a NOEL of 5630 mg kg(-1) day(-1). Developmental toxicity, expressed as fetotoxicity, had a NOEL of 5630 mg kg(-1) day(-1) with the rat and 563 mg kg(-1) day(-1) with mice. Neither species showed any evidence of embryotoxicity or teratogenicity. There was no evidence for reproductive toxicity with mice given up to 3% TEG in drinking water in a continuous breeding study. TEG did not produce mutagenic or clastogenic effects in the following in vitro genetic toxicology studies: Salmonella typhimurium reverse mutation test, SOS-chromotest in E. coli, CHO forward gene mutation test (HGPRT locus), CHO sister chromatid exchange test, and a chromosome aberration test with CHO cells. The use patterns suggest that exposure to TEG is mainly occupational, with limited exposures by consumers. Exposure is normally by skin and eye contact. Local and systemic adverse health effects by cutaneous exposure are likely not to occur, and eye contact will produce transient irritation without corneal injury. The very low vapor pressure of TEG makes it unlikely that significant vapor exposure will occur. Aerosol exposure is not a usual exposure mode, and acute aerosol exposures are unlikely to be harmful, although a peripheral sensory irritant effect may develop. However, repeated exposures to a TEG aerosol may result in respiratory tract irritation, with cough, shortness of breath and tightness of the chest. Recommended protective and precautionary measures include protective gloves, goggles or safety glasses and mechanical room ventilation. LC(50) data to various fish, aquatic invertebrates and algae, indicate that TEG is essentially nontoxic to aquatic organisms. Also, sustained exposure studies have demonstrated that TEG is of a low order of chronic aquatic toxicity. The bioconcentration potential, environmental hydrolysis, and photolysis rates are low, and soil mobility high. In the atmosphere TEG is degraded by reacting with photochemically produced hydroxyl radicals. These considerations indicate that the potential for ecotoxicological effects with TEG is low.     

Use of health hazard criteria for estimating the hazard potential of chemicals to water in case of a spill

Accidental spills resulting in severe pollution can occur during transportation or handling of large volumes of chemicals. To address this problem, chemicals are classified according to the level of hazard to man and the environment in order to then define graduated technical standards. Three regulatory examples (enforced or drafted for transport and industrial installations in Europe) covering aspects of limnic as well as sea water are discussed in regard to health aspects of pollution. Whereas for the safety of seagoing tankships an exposure orientated combination of health and environmental aspects is used, for industrial plants in Germany a scoring system based on the European Union's Risk Phrase system is applied. The health-related parameters primarily used for hazard classification are repeated-dose toxicity and acute oral and dermal toxicity. Acute oral toxicity is most widely used because of the ready availability of data. Carcinogenicity is treated as the most important hazard. The report discusses the importance of dermal exposure, aspiration, and endocrine disruption as parameters as well as the importance of health criteria for the protection of aquatic organisms.     

Pulmonary toxicity study in rats with three forms of ultrafine-TiO2 particles: differential responses related to surface properties

Surface properties are critical to assess effects of ultrafine-TiO(2) particles. The aim of this study was to assess lung toxicity in rats of newly developed, well characterized, ultrafine-TiO(2) particles and compare them to TiO(2) samples in two different size ranges and surface modifications. Groups of rats were intratracheally instilled with doses of 1 or 5mg/kg of either two ultrafine rutile TiO(2) particles (uf-1 or uf-2); rutile R-100 fine-TiO(2) (F-1); 80/20 anatase/rutile P25 ultrafine-TiO(2) (uf-3); or alpha-quartz particles. Phosphate-buffered saline (PBS) solution instilled rats served as vehicle controls. Following exposures, the lungs of PBS and particle-exposed rats were evaluated for bronchoalveolar lavage (BAL) fluid inflammatory markers, cell proliferation, and by histopathology at post-instillation time points of 24h, 1 week, 1 and 3 months. The ranking of lung inflammation/cytotoxicity/cell proliferation and histopathological responses was quartz>uf-3>F-1=uf-1=uf-2. Exposures to quartz and to a lesser degree, uf-3 anatase/rutile TiO(2) particles produced pulmonary inflammation, cytotoxicity and adverse lung tissue effects. In contrast, exposures to F-1 fine-TiO(2) particles or to uf-1/uf-2 ultrafine-TiO(2) particle-types produced transient inflammation. We conclude that differences in responses to anatase/rutile uf-3 TiO(2) particles versus the rutile uf-1 and uf-2 TiO(2) particles could be related to crystal structure, inherent pH of the particles, or surface chemical reactivity. Thus, based on these results, inhaled rutile ultrafine-TiO(2) particles are expected to have a low risk potential for producing adverse pulmonary health effects. Finally, the results demonstrate that exposures to ultrafine-TiO(2) particle-types can produce differential pulmonary effects, based upon their composition, and crystal structure. Thus, the lung toxicity of anatase/rutile uf-3 should not be viewed as representative for all ultrafine-TiO(2) particle-types.     

Safety and toxicological evaluation of undenatured type II collagen

Previous research has shown that undenatured type II collagen is effective in the treatment of arthritis. The present study evaluated the broad-spectrum safety of UC-II by a variety of toxicological assays including acute oral, acute dermal, primary dermal irritation, and primary eye irritation toxicity. In addition, genotoxicity studies such as Ames bacterial reverse mutation assay and mouse lymphoma tests, as well as a dose-dependent 90-day sub-chronic toxicity study were conducted. Safety studies indicated that acute oral LD₅₀ of UC-II was greater than 5000?mg/kg in female Sprague-Dawley rats. No changes in body weight or adverse effects were observed following necropsy. Acute dermal LD₅₀ of UC-II was determined to be greater than 2000?mg/kg. Primary skin irritation tests conducted on New Zealand Albino rabbits classified UC-II as slightly irritating. Primary eye irritation tests conducted on rabbits indicated that UC-II was moderately irritating to the eye. UC-II did not induce mutagenicity in the bacterial reverse mutation test in five Salmonella typhimurium strains either with or without metabolic activation. Similarly, UC-II did not induce a mutagenic effect in the gene mutation test in mouse lymphoma cells either with or without metabolic activation. A dose-dependent 90-day sub-chronic toxicity study revealed no pathologically significant changes in selected organ weights individually or as percentages of body or brain weights. No significant changes were observed in hematology and clinical chemistry. Therefore, the results from the current study show a broad-spectrum safety profile of UC-II.     

Hazard assessment of commonly used agricultural antibiotics on aquatic ecosystems

In this study, eleven commonly used antibiotics including sulfonamides, tetracyclines, aminoglycosides, fluoroquinolones, and beta-lactams were evaluated for their acute and chronic aquatic toxicities using standard test organisms e.g., Vibrio fischeri, Daphnia magna, Moina macrocopa, and Oryzias latipes. Among the antibiotics tested for acute toxicity, neomycin was most toxic followed by trimethoprim, sulfamethoxazole and enrofloxacin. Sulfamethazine, oxytetracycline, chlortetracycline, sulfadimethoxine and sulfathiazole were of intermediate toxicity, while ampicillin and amoxicillin were least toxic to the test organisms. There were no trends in sensitivity among test organisms or among different classes of the antibiotics. Only the beta-lactam class was the least toxic. In chronic toxicity test, neomycin affected reproduction and adult survival of D. magna and M. macrocopa with low mg/l levels exposure. Predicted no effect concentrations (PNECs) were derived from the acute and chronic toxicity information gleaned from this study and from literature. When the PNECs were compared with measured environmental concentrations (MECs) reported elsewhere for the test compounds, hazard quotients for sulfamethoxazole, sulfathiazole, chlortetracycline, oxytetracycline, and amoxicillin exceeded unity, which suggests potential ecological implication. Therefore, further studies including monitoring and detailed toxicological studies are required to assess potential ecological risk of these frequently used veterinary antibiotics.     

Safety and toxicological evaluation of a novel chromium(III) dinicocysteinate complex

Chromium(III) is an essential trace element required for normal protein, fat and carbohydrate metabolism. It also helps in energy production and increasing lean body mass. Chromium(III) dinicocysteinate (CDNC) is a unique form of bioavailable chromium(III). This study was focused on determining the broad spectrum safety of CDNC. Acute oral, acute dermal, primary dermal and eye irritation studies, Ames’ bacterial reverse mutation assay, mammalian erythrocyte micronucleus test, and a 90-day dose-dependent oral toxicity study were conducted. Acute oral and dermal LD₅₀ of CDNC was found to be greater than 2000?mg/kg in Sprague-Dawley rats. A primary skin irritation study in New Zealand Albino rabbits demonstrated CDNC as slightly irritating. An eye irritation study exhibited that CDNC is moderately irritating. Ames’ bacterial reverse mutation assay and mammalian erythrocyte micronucleus test demonstrated CDNC as non-mutagenic. A dose-dependent 90-day oral toxicity study demonstrated no significant toxicity of CDNC. Body weight, food and water consumption, selected organ weights (expressed as percentages of body or brain weights), ocular health, hematology, blood chemistry, and histopathology showed no abnormal changes. Clinical and histopathological evaluation of CDNC identified a dose level of 5.7?mg/kg/day as the no observed adverse effect level (NOAEL). Overall, these results demonstrate the broad spectrum safety of CDNC.     

Relevance of the developmental toxicity of ethanol in the occupational setting: a review

Numerous studies have been conducted investigating the reproductive toxicology of ethanol, the overwhelming majority concerning the adverse effects of consuming alcohol in beverages during pregnancy. Because many of the in vivo studies were designed to model alcoholism, they used comparatively high doses and assessed relatively few endpoints. Outcomes may have been affected by disturbances of metabolism at such high exposures, giving rise to secondary effects on development. The available data on ethanol from "conventional" developmental toxicity study test methods of the type used for regulatory hazard assessment of chemicals are limited. It is in this context, however, i.e. the use of ethanol as an industrial chemical rather than as a component of beverages, that this review is based. Using the usual criteria applied for the purpose of hazard assessment of industrial chemicals, it is concluded that there is no evidence that industrial exposure to ethanol is a developmental toxicity hazard. Developmental toxicity may result from drinking alcoholic beverages, the threshold level for all aspects of which has yet to be de fi ned. This is not, however, considered relevant to the low blood alcohol concentrations resulting from any conceivable inhalation or dermal exposure in the workplace or through the directed use of any consumer product containing ethanol.     

Acute,Subchronic, and Mutagenicity Studies with Norbornene Fluoroalcohol

The object of this study was to evaluate the toxicity of norbornene fluoroalcohol (NBFOH), which is used as an intermediate in the production of fluorinated monomers and polymers. NBFOH was evaluated for acute oral, dermal, and inhalation toxicity, dermal sensitization using the Local Lymph Node Assay (LLNA), mutagenesis by the Ames assay, and subchronic toxicity in a 4-week inhalation rat study. NBFOH demonstrated slight acute toxicity in oral, dermal, and inhalation studies. Approximate lethal doses of 3400 and > 5000 mg/kg for the oral and dermal routes, respectively, and an approximate lethal concentration of 4300 mg/m³ were determined. NBFOH demonstrated moderate skin irritation, was a severe eye irritant, produced dermal sensitization, but did not cause bacterial mutagenicity either in the presence or absence of S9 activation. Male and female rats were exposed nose only to airborne NBFOH at levels of 0, 410, 1400, and 1500 mg/m³, 6 h/day, 5 days/week for 4 weeks with clinical and histopathology specimens collected 1 day after the final exposure. Due to the vapor pressure of NBFOH, the 1500 mg/m³ atmosphere was 27% aerosol and 73% vapor; the 1400 mg/m³ atmosphere was 5% aerosol and 95% vapor, and the 410 mg/m³ level was only vapor. No test substance–related mortality or clinical signs of toxicity were observed over the course of the study, and male rats demonstrated significant weight loss and decreased food consumption at 1400 mg/m³. Male rats from the 1500 mg/m³ group demonstrated an 11% increase in prothrombin time that was significantly higher than the control value. Examination of fluoride in the urine did not demonstrate a concentration–response relationship, with minimal elevations observed in male rats at all exposure levels and sporadic increases in females. Both male and female rats exposed to 1400 mg/m³ or greater had squamous metaplasia of the laryngeal mucosa and degeneration of the nasal olfactory and respiratory mucosa. Based on the above findings, NBFOH demonstrates the potential to produce allergic contact dermatitis, and subchronic inhalation studies indicate a no-observed-adverse-effect-level (NOAEL) of 410 mg/m³.     

An alternative approach for the safety evaluation of new and existing chemicals, an exercise in integrated testing

Various in vitro and in silico methods without animals were applied to 10 substances listed on ELINCS with a complete VIIA base-set available at NOTOX. The hazard assessment for these substances was performed on basis of available non-animal data, QSAR, PBBK-modelling and additional, new in vitro testing was applied. Based on these data predictions on fish toxicity, acute toxicity, skin- and eye-irritation, sensitisation, and toxicity after repeated dosing were made. The predictions were compared with the outcome of the in vivo tests. Nine out of ten predictions on fish LC(50) proved to be correct. For skin- and eye-irritation 70% was predicted correctly. Sensitisation was predicted correctly for 7 out of 10 substances, but three false negatives were found. Acute oral toxicity (LD(50)) and repeated dose toxicity were less successful (5 out of 10 and 2 out of 10 correct predictions, respectively); application of the PBBK model proved successful. Acute dermal toxicity was predicted correctly in 9 out of 10 cases. In general an over-estimation of systemic toxicity was found, which can be explained by an over-prediction of cytotoxicity and worst case assumptions on absorption and binding to (plasma) proteins. This integrated approach leads to a 38% reduction of laboratory animals.     

Pulmonary exposures to Sepiolite nanoclay particulates in rats: Resolution following multinucleate giant cell formation

Sepiolite is a magnesium silicate-containing nanoclay mineral and is utilized as a nanofiller for nanocomposite applications. We postulated that lung exposures to Sepiolite clay samples could produce sustained effects. Accordingly, the pulmonary and extrapulmonary systemic impacts in rats of intratracheally instilled Sepiolite nanoclay samples were compared with quartz or ultrafine (uf) titanium dioxide particle-types at doses of 1 mg/kg or 5 mg/kg. All particulates were well characterized, and dedicated groups were evaluated by bronchoalveolar lavage, lung cell proliferation, macrophage functional assays and full body histopathology at selected times postexposure (pe). Bronchoalveolar lavage results demonstrated that quartz particles produced persistent, dose-dependent lung inflammatory responses measured from 24 h through 3 months pe. Exposures to uf TiO₂ particles or Sepiolite samples produced transient neutrophilic responses at 24-h pe; however, unlike the other particle-types, Sepiolite exposures produced macrophage-agglomerates or multinucleate giant cells at 1 week, 5 weeks and 3 months pe. In vitro alveolar macrophage functional studies demonstrated that mononuclear cells recovered from quartz but not Sepiolite or uf TiO₂-exposed rats were deficient in their chemotactic capacities. Moreover, lung parenchymal cell proliferation rates were increased in rats exposed to quartz but not Sepiolite or uf TiO₂ particles. Histopathological evaluation of lung tissues revealed that pulmonary exposures to Sepiolite nanoclay or quartz samples produced inflammation in centriacinar regions at 24-h pe but the effects decreased in severity over time for Sepiolite and increased for quartz-exposed rats. The quartz-induced lesions were progressive and were characterized at 3 months by acinar foamy alveolar macrophage accumulation and septal thickening due to inflammation, alveolar Type II cell hyperplasia and collagen deposition. In the Sepiolite nanoclay group, the finding of multinucleated giant cell accumulation associated with minor collagen deposition in acinar regions was rarely observed. Exposures to ultrafine TiO₂ produced minimal effects characterized by the occurrence of phagocytic macrophages in alveolar ducts. Full body histopathology studies were conducted at 24 h and 3 months post particle exposures. Histopathological evaluations revealed minor particle accumulations in some mediastinal or thoracic lymph nodes. However, it is noteworthy that no extrapulmonary target organ effects were observed in any of the particle-exposed groups at 3 months postexposure.     

Acute dermal toxicity of two quarternary organophosphonium salts in the rabbit

Tetrabutyl phosphonium chloride and tetrabutyl phosphonium bromide were evaluated for their potential to cause primary dermal irritation and acute dermal toxicity in rabbits. Both chemicals were found to not only be severely irritating to skin, but the pure hygroscopic chemicals caused death in more than half the number of rabbits used in the primary dermal irritation tests. Further investigations revealed the single-application dermal LD50 of tetrabutyl phosphonium chloride (Bu4PCl) (using an ethylene carbonate (EC) vehicle) was 600 mg/kg for male rabbits and 500 mg/kg for female rabbits. The single-application dermal LD50 of tetrabutyl phosphonium bromide (Bu4PBr) (using the EC vehicle) was 700 mg/kg for male rabbits and 850 mg/kg for female rabbits. The dermal LD50 of pure undiluted Bu4PCl was 225 mg/kg for male rabbits. These data indicate that Bu4PCl and Bu4PBr represent a substantial acute dermal toxicity hazard.