Simulated downwind coal combustion emissions for laboratory inhalation exposure atmospheres

Exposure atmospheres for rodent inhalation toxicology studies were generated to enable the evaluation of biological responses to a simulated downwind coal combustion atmosphere. A composition representing a single test case of emissions components as they may exist tens to hundreds of miles from a coal-fired power plant was developed. The particulate matter (PM) was 99% sulfate (partially neutralized) and 1% ash. Sulfate was present in equimolar concentrations to sulfur dioxide (SO?). Gaseous nitrogen species included nitrogen monoxide (NO), nitrogen dioxide (NO?), and nitric acid (HNO?). At the high-exposure level, the gaseous species target concentrations were 0.2?ppm SO?, 0.6?ppm NO, 0.3?ppm NO?, and 0.1?ppm HNO?. The test atmosphere was produced by combining effluent from a laboratory coal combustor with sulfate generated through an evaporation-condensation generator. These atmospheres were used to conduct inhalation toxicology studies that have been previously reported.     

Health effects of subchronic inhalation exposure to simulated downwind coal combustion emissions

Context: There have been no animal studies of the health effects of repeated inhalation of mixtures representing downwind pollution from coal combustion. Environmental exposures typically follow atmospheric processing and mixing with pollutants from other sources.

Objective: This was the fourth study by the National Environmental Respiratory Center to create a database for responses of animal models to combustion-derived pollutant mixtures, to identify causal pollutants—regardless of source.

Methods: F344 and SHR rats and A/J, C57BL/6, and BALB/c mice were exposed 6?h/day 7 days/week for 1 week to 6 months to three concentrations of a mixture simulating key components of “downwind” coal combustion emissions, to the highest concentration filtered to remove particulate matter (PM), or to clean air. Emissions from low-sulfur subbituminous coal were modified to create a mixture recommended by an expert workshop. Sulfur dioxide, nitrogen oxides, and PM were the dominant components. Nonanimal-derived PM mass concentrations of nominally 0, 100, 300, and 1000 µg/m³ were mostly partially neutralized sulfate.

Results: Only17 of 270 species-gender-time-outcome comparisons were significantly affected by exposure; some models showed no effects. There was strong evidence that PM participated meaningfully in only three responses.

Conclusion: On a total mass or PM mass basis, this mixture was less toxic overall than diesel and gasoline exhausts or wood smoke. The largely sulfate PM contributed to few effects and was the sole cause of none. The study did not allow identification of causal pollutants, but the potential role of NOx in some effects is suggested by the literature.     

A new inhalation exposure system for the determination of inhaled doses in laboratory rats

A new inhalation exposure system has been developed which allows the determination of inhaled doses of vapors and gases by laboratory rats. The system consists of saran bags connected to head-only exposure cylinders via one-way valves. One bag serves as the source of contaminant and another receives expired air. The exposure cylinders also serve as whole body plethysmographs. Up to three rats can be exposed concurrently to the same concentration of test material. The construction of the system and its use for inhalation exposures to a direct-acting radiolabeled carcinogen are described.     

Generation and characterization of diesel engine combustion emissions from petroleum diesel and soybean biodiesel fuels and application for inhalation exposure studies

Abstract

Biodiesel made from the transesterification of plant- and animal-derived oils is an important alternative fuel source for diesel engines. Although numerous studies have reported health effects associated with petroleum diesel emissions, information on biodiesel emissions are more limited. To this end, a program at the U.S. EPA assessed health effects of biodiesel emissions in rodent inhalation models. Commercially obtained soybean biodiesel (B100) and a 20% blend with petroleum diesel (B20) were compared to pure petroleum diesel (B0). Rats and mice were exposed independently for 4?h/day, 5?days/week for up to 6?weeks. Exposures were controlled by dilution air to obtain low (50?µg/m³), medium (150?µg/m³) and high (500?µg/m³) diesel particulate mass (PM) concentrations, and compared to filtered air. This article provides details on facilities, fuels, operating conditions, emission factors and physico-chemical characteristics of the emissions used for inhalation exposures and in vitro studies. Initial engine exhaust PM concentrations for the B100 fuel (19.7?±?0.7?mg/m³) were 30% lower than those of the B0 fuel (28.0?±?1.5?mg/m³). When emissions were diluted with air to control equivalent PM mass concentrations, B0 exposures had higher CO and slightly lower NO concentrations than B100. Organic/elemental carbon ratios and oxygenated methyl esters and organic acids were higher for the B100 than B0. Both the B0 and B100 fuels produced unimodal-accumulation mode particle-size distributions, with B0 producing lower concentrations of slightly larger particles. Subsequent papers in this series will describe the effects of these atmospheres on cardiopulmonary responses and in vitro genotoxicity studies.     

Effects of simulated downwind coal combustion emissions on pre-existing allergic airway responses in mice

Context: Coal-fired power plant emissions can contribute a significant portion of the ambient air pollution in many parts of the world.

Objective: We hypothesized that exposure to simulated downwind coal combustion emissions (SDCCE) may exacerbate pre-existing allergic airway responses.

Methods: Mice were sensitized and challenged with ovalbumin (OVA). Parallel groups were sham-sensitized with saline. Mice were exposed 6?h/day for 3 days to air (control, C) or SDCCE containing particulate matter (PM) at low (L; 100 μg/m³), medium (M; 300 μg/m³), or high (H; 1000 μg/m³) concentrations, or to the H level with PM removed by filtration (high-filtered, HF). Immediately after SDCCE exposure, mice received another OVA challenge (pre-OVA protocol). In a second (post-OVA) protocol, mice were similarly sensitized but only challenged to OVA before air/SDCCE. Measurement of airway hyperresponsiveness (AHR), bronchoalveolar lavage (BAL), and blood collection were performed ~24?h after the last exposure.

Results: SDCCE significantly increased BAL macrophages and eosinophils in OVA-sensitized mice from the post-OVA protocol. However, there was no effect of SDCCE on BAL macrophages or eosinophils in OVA-sensitized mice from the pre-OVA protocol. BAL neutrophils were elevated following SDCCE in both protocols in nonsensitized mice. These changes were not altered by filtering out the PM. In the post-OVA protocol, SDCCE decreased OVA-specific IgG₁ in OVA-sensitized mice but increased levels of total IgE, OVA-specific IgE and OVA-specific IgG₁ and IgG_2a in non-sensitized animals. In the pre-OVA protocol, SDCCE increased OVA-specific IgE in both sensitized and non-sensitized animals. Additionally, BAL IL-4, IL-13, and IFN-γ levels were elevated in sensitized mice.

Conclusion: These results suggest that acute exposure to either the particulate or gaseous phase of SDCCE can exacerbate various features of allergic airway responses depending on the timing of exposure in relation to allergen challenge.     

Comparative pulmonary toxicological assessment of oil combustion particles following inhalation or instillation exposure.

Controversy persists regarding the validity of intratracheal instillation (IT) of particulate matter (PM) as a surrogate for inhalation exposure (IH) in rodents. Concerns center on dose, dose-rate, and distribution of material within the lung. Acute toxicity of a residual oil fly ash (ROFA) administered by IH was compared to those effects of a single IT bolus at an IH-equivalent dose. Male Sprague Dawley rats (60 days old) were exposed by nose-only IH to approximately 12 mg/m3 for 6 h. Inter-lobar dose distribution of ROFA, dissected immediately post exposure, was assayed by neutron activation. Vanadium and nickel were used as ROFA markers. IT administration of the IH-equivalent dose (110 microg) showed similar (<15%) interlobular distribution, with the exception of the inferior lobe dose (IT>IH approximately 25%). Evaluation of airway hyperreactivity (AHR), bronchoalveolar lavage fluid (BALF) constituents, and histopathology was conducted at 24, 48, and 96 h post exposure. AHR in the IH group was minimally (p > 0.05) affected by treatment, but was significantly increased ( approximately 40%) at both 24 and 48 h post IT. Inflammation in both groups, as measured by alterations in BALF protein, lactate dehydrogenase and neutrophils, was virtually identical at all time points. Alveolitis and bronchial inflammation/epithelial hypertrophy were prominent 24 h following IT, but not apparent after IH. Conversely, alveolar hemorrhage, congestion, and airway exudate were pronounced at 48 h post-IH but not remarkable in the IT group. Thus, IT-ROFA mimicked IH in terms of lobar distribution and injury biomarkers over 96 h, while morphological alterations and AHR appeared to be more dependent on the method of administration.     

Behavioural effects of prenatal metallic mercury inhalation exposure in rats

The effects of administration by inhalation of metallic mercury vapour (Hg⁰) to pregnant rats, approximately corresponding to doses of 0.2 mg Hg⁰/kg /day (high dose) or 0.07 mg Hg⁰/kg/day (low dose), on the developmental and behavioural repertoire of the offspring were studied. Exposure occurred during days 11–14 plus 17–20 of gestation. The dose levels were selected so as not to induce maternal toxicity. Maturation variables such as surface righting, negative geotaxis, pinna unfolding, and tooth eruption revealed no differences between Hg⁰-treated offspring and controls. Tests of spontaneous motor activity showed that the Hg⁰-treated offspring were hypoactive at 3 months of age but hyperactive at 14 months. In spatial learning tasks the prenatally exposed offspring showed retarded acquisition in the radial arm maze but no differences in circular swim maze. A simple test of learning, habituation to a novel environment (activity chambers), indicated a reduced ability to adapt. These data suggest that prenatal exposure to Hg⁰ vapour results in similar behaviour changes in the offspring as reported for methylmercury.     

Development of a large-scale computer-controlled ozone inhalation exposure system for rodents

Objective: Complete systems for laboratory-based inhalation toxicology studies are typically not commercially available; therefore, inhalation toxicologists utilize custom-made exposure systems. Here we report on the design, construction, testing, operation and maintenance of a newly developed in vivo rodent ozone inhalation exposure system.

Materials and methods: Key design requirements for the system included large-capacity exposure chambers to facilitate studies with large sample sizes, automatic and precise control of chamber ozone concentrations, as well as automated data collection on airflow and environmental conditions. The exposure system contains two Hazelton H-1000 stainless steel and glass exposure chambers, each providing capacity for up to 180 mice or 96 rats. We developed an empirically tuned proportional-integral-derivative control loop that provides stable ozone concentrations throughout the exposure period (typically 3h), after a short ramp time (～8?min), and across a tested concentration range of 0.2–2?ppm. Specific details on the combination of analog and digital input/output system for environmental data acquisition, control and safety systems are provided, and we outline the steps involved in maintenance and calibration of the system.

Results: We show that the exposure system produces consistent ozone exposures both within and across experiments, as evidenced by low coefficients of variation in chamber ozone concentration and consistent biological responses (airway inflammation) in mice, respectively.

Conclusion: Thus, we have created a large and robust ozone exposure system, facilitating future studies on the health effects of ozone in rodents.     

HPLC法测定复方异丙托溴铵吸入溶液两组分的含量

目的:建立高效液相色谱法同时测定复方异丙托溴铵吸入溶液中异丙托溴铵和硫酸沙丁胺醇两组分的含量。方法:采用Inertsil ODS-3 C18(150 mm×4.6 mm,5μm)色谱柱,流动相为0.01 mol.L-1磷酸二氢钾溶液(用磷酸调节pH 2.3)(A)-乙腈(B),梯度洗脱,流速1.0 mL.min-1,检测波长为220 nm(检测异丙托溴铵)和276 nm(检测沙丁胺醇),柱温40℃。结果:异丙托溴铵和沙丁胺醇进样量分别在0.01~0.2 mg.mL-1和0.05~1.0 mg.mL-1范围内线性关系良好(r均为0.9999,n=5),回收率(n=9)分别为100.2%和100.3%。结论:本测定方法准确、灵敏,专属性高,可同时测定复方异丙托溴铵吸入溶液中异丙托溴铵和硫酸沙丁胺醇两组分的含量。     

偏二甲基肼吸入染毒在家兔体内的毒物动力学

家兔吸入３７０±２８和７７６±５３ｍｇ·ｍ－３：以及恒速静脉输注９．７ｍｇ·ｋｇ－１·ｈ－１偏二甲基肼（ＵＤＭＨ）．均以一房室模型在体内配置；而ｉｖ３９．０ｍｇ·ｋｇ－１ＵＤＭＨ呈二房室模型。ＵＤＭＨ蒸气经家兔呼吸道的滞留率高达９５％以上，不受吸入气ＵＤＭＨ蒸气浓度Ｃ１和动物通气量Ｖｒ改变和波动的影响。由于实验期间Ｃ１和Ｖｒ基本稳定，因此ＵＤＭＨ以近似恒速即表现零级速度滞留在呼吸道，并以同样的速度特征全部迅速地被吸收入血。家兔ｉｖＵＤＭＨ在家兔体内分布很快，１３ｍｉｎ左右分布相即基本结束；呈全身分布。ＵＤＭＨ从家免体内消除较快，物质蓄积性弱；存在肾外消除途径。     

Evaluation of newly developed nose-only inhalation exposure chamber for nanoparticles

In this study, a direct-flow-type nose-only exposure chamber developed for inhalation toxicity experiments using a numerical analysis and experiments is evaluated. Maintaining a uniform flow rate and test article concentration are the critical factors when designing an inhalation exposure chamber. Therefore, this study evaluated whether the flow rate and particle size distribution at the injection nozzles at each port could be maintained with a deviation below 10%. To achieve this requirement, a nose-only exposure chamber flow field was simulated using a numerical analysis method, i.e. computational fluid dynamics (CFD) code FLUENT 6.3.26. Based on the simulation results, a test chamber was built and tested. The flow velocity was measured at the injection nozzle of the chamber and the aerosol particle size distribution was also measured at each port while inserting the test material into the exposure chamber. The results indicated that a uniform flow field distribution at each stage and port, the deviation of the flow velocity, and particle size distribution were all within 10%. Thus, the resulting nose-only exposure chamber could be described as well-designed.     

Montelukast prevents vascular endothelial dysfunction from internal combustion exhaust inhalation during exercise

Associations between high particulate matter (PM) pollution and increased morbidity and mortality from coronary heart disease have been identified. This study assessed leukotriene (LT) participation in PM-induced vascular endothelial dysfunction. Ten healthy males exercised 4 times for 30?min in both high PM (550,286?±?42,004 particles·cm^?3) and low PM (4571?±?1922 particles·cm^?3) after ingesting placebo (PL) or 10?mg montelukast (MK; half-life 3–6?h), a leukotriene receptor antagonist. Brachial artery flow-mediated dilation (FMD) was measured pre- and 30?min, 4?h, 24?h post-exercise. No basal brachial artery vascoconstriction was evident from high PM exercise. High PM blunted FMD, whereas high PM MK, low PM PL, and low PM MK demonstrated normal FMD (p < .003). Change in FMD (pre- to post-exercise) for high PM PL was different than for high PM MK, low PM PL, and low PM MK at 30?min post-exercise (p?<?.007). At 4?h, high PM MK FMD blunting increased (p?=?.1). At 24?h, high PM FMD blunting persisted (p?<?.05); no difference was observed between high PM PL or MK treatment, but was different that low PM PL/MK treatments (p?<?.05). MK blocked high PM post-exercise FMD blunting and maintained normal response, suggesting that leukotrienes are involved in PM-initiated vascular endothelial dysfunction.     

沙丁胺醇与硫酸镁联合雾化吸入治疗支气管哮喘的临床疗效观察

目的 评价沙丁胺醇与硫酸镁联合雾化吸入治疗支气管哮喘的临床效果。方法 选取科右前旗人民医院2013年3月到2015年3月门诊确认的100名支气管哮喘的患者为研究对象,按照随机以及结合患者意愿的方法分为观察组与对照组。两组患者在年龄、性别、病情等方面差异无统计学意义。对照组给予沙丁胺醇雾化吸入治疗,观察组给予沙丁胺醇与硫酸镁联合雾化吸入治疗。通过检测患者的肺功能恢复情况,第一秒用力呼气量(FEV1)、最大呼气流量(PEF),评价此种方法的临床效果以及安全性。结果 两组患者在治疗后,FEV1与PEF相对比激发值均有提高(P<0.05);观察组的患者的FEV1与PEF的上升率高于对照组(P<0.05),且恢复后的FEV1与PEF值高于对照组。在20 min后,患者的肺功能值恢复至正常值。在观察组中出现1(2%)例副作用的患者。结论 沙丁胺醇与硫酸镁雾化吸入对于支气管哮喘的治疗有积极的临床治疗效果,但是对于进一步的使用,需要进行更深的研究与探索,减少其对患者的副作用。     

Development of a chronic inhalation reference value for hexamethylenediamine using an exposure model based on the dihydrochloride salt

Abstract

The Texas Commission on Environmental Quality has developed a chronic inhalation Reference Value (ReV) for hexamethylenediamine (HMDA, CAS 124-09-4) based on respiratory effects identified in an animal study. HMDA is used in the fiber and plastics industry as an intermediate in the production of nylon, high-strength resins and polyamide adhesives. As a toxicant, HMDA acts primarily as a respiratory irritant with effects occurring in the upper respiratory tract, although systemic effects have been noted at higher concentrations. ReVs are chemical-specific air concentrations derived to protect human health. Acute and chronic ReVs were developed for HDMA based on an inhalation study conducted by the National Toxicology Program (NTP), which used the salt of HMDA, hexamethylenediamine dihydrochloride (HDDC, CAS 6055-52-3). For the chronic evaluation, rats and mice were exposed to 0, 1.6, 5, 16, 50 and 160?mg HDDC/m³ for 13 weeks. The critical effect identified for the most sensitive species was hyaline degeneration in the olfactory epithelium in mice. The data provided in this study were suitable to benchmark concentration (BMC) modeling. Dosimetric adjustments using the rat and mouse Multiple-Path Particle Dosimetry Model (version 3.0) were made to the 95% lower limit of the BMC(10) to determine the human equivalent point of departure. Uncertainty factors were applied to account for variation in sensitivity within the human population, toxicodynamic differences between mice and humans, and use of a subchronic study. The ReV was initially calculated for HDDC and then adjusted for HMDA. The chronic ReV is 1.8?µg/m³ for respirable HMDA?≤?10?µm in diameter.     

Computer controlled multi-walled carbon nanotube inhalation exposure system

Inhalation exposure systems are necessary tools for determining the dose–response relationship of inhaled toxicants under a variety of exposure conditions. The objective of this project was to develop an automated computer controlled system to expose small laboratory animals to precise concentrations of airborne multi-walled carbon nanotubes (MWCNT). An aerosol generator was developed which was capable of suspending a respirable fraction of multi-walled carbon nanotubes from bulk material. The output of the generator was used to expose small laboratory animals to constant aerosol concentrations up to 12?mg/m³. Particle distribution and morphology of the MWCNT aerosol delivered to the exposure chamber were measured and compared to samples previously taken from air inside a facility that produces MWCNT. The comparison showed the MWCNT generator was producing particles similar in size and shape to those found in a work environment. The inhalation exposure system combined air flow controllers, particle monitors, data acquisition devices, and custom software with automatic feedback control to achieve constant and repeatable exposure chamber temperature, relative humidity, pressure, aerosol concentration, and particle size distribution. The automatic control algorithm was capable of maintaining the mean aerosol concentration to within 0.1?mg/m³ of the selected target value, and it could reach 95% of the target value in less than 10?minutes during the start-up of an inhalation exposure. One of the major advantages of this system was that once the exposure parameters were selected, a minimum amount of operator intervention was required over the exposure period.     

Acute nose-only inhalation exposure of rats to di- and triphosgene relative to phosgene

Groups of young adult Wistar rats were acutely exposed to trichloromethyl chloroformate (diphosgene) and bis(trichloromethyl) carbonate (triphosgene) vapor atmospheres using a directed-flow nose-only mode of exposure. The exposure duration used was 240?min. The median lethal concentration (LC₅₀) of diphosgene and triphosgene was 13.9 and 41.5?mg/m³, respectively. Based on the molar exposure concentrations, the LC₅₀s of phosgene (previously published), diphosgene, and triphosgene were 0.07, 0.07, and 0.14 mmol/m³, respectively. Although the principal toxic mode of action of the volatile diphosgene was similar to phosgene gas, the vapor phase of triphosgene appeared to be different to that of phosgene and diphosgene based on a more persistent occurrence of signs of respiratory distress and a biphasic onset of mortality. While all substances caused mortality within 1 day postexposure, triphosgene induced a second phase of mortality 11–14 days postexposure. The vapor saturation concentration of triphosgene at ambient temperature is ≈100 times its LC₅₀. In summary, triphosgene-induced lung injury patterns are different from that of phosgene and diphosgene. More research is needed to close the substantial data gaps of triphosgene.     

Subacute inhalation toxicity assessment of fly ash from industrial waste incinerators

Fly ash from industrial waste incinerators has been a significant concern because of their constituent toxic heavy metals and organic compounds. The objective of this study was to identify the subacute inhalation toxicity of fly ash from industrial waste incinerators, using whole body inhalation exposure chambers. Male and female groups of Sprague-Dawley rats were exposed to fly ash by inhalation of concentrations of 0, 50, 100, 200?mg/m³, for 6?h/day, 5 days/week for 4 weeks. There was no significant difference in body weight, and relative organ weight to body weight, between the exposure groups and the control group. Hematological examinations revealed a significant increase of monocyte counts in fly ash exposed rats and brown pigment laden macrophage was found in the lungs of rats exposed to high concentration of fly ash. A decrease of blood glucose levels and an increase in glutamate oxaloacetate transaminase activity were observed in fly ash treated rats. There was also a significant increase of lactate dehydrogenase levels in rat blood exposed fly ash. A significant dose-dependent increase of DNA damage was found in lymphocytes, spleen, bronchoalveolar lavage, liver, lung, and thymus of rats exposed to fly ash. In addition, the level of lipid peroxidation was increased in the plasma of rats exposed to a high concentration of fly ash. These results suggest that inhalation of fly ash from industrial waste incinerators can induce histopathologic, hematological, and serum biochemical changes and oxidative damage.