Chronic Inhalation Studies Research Articles

Possible mechanisms to explain dust overloading of the lungs

This paper briefly reviews the available evidence on dust overloading of the lungs, a condition which has come to the forefront in many recently reported chronic inhalation studies. A general hypothesis is developed that dust overloading, which is typified by a progressive reduction of particle clearance from the deep lung, reflects a breakdown in alveolar macrophage (AM)-mediated dust removal due to the loss of AM mobility. The inability of the dust-laden AMs to translocate to the mucociliary escalator is correlated to an average composite particle volume per alveolar macrophage in the lung. When this particulate volume exceeds approximately 60 μm 3/AM, on the basis of a uniform distribution of particles over the AM pool size (∼ 2.5 × 10 7 cells) in the Fischer 344 rat, the overload effect appears to be initiated. When the distributed particulate volume exceeds ∼ 600 μm 3 per cell, the evidence suggests that AM-mediated particle clearance virtually ceases and agglomerated particle-laden macrophages remain in the alveolar region. This paper considers possible mechanisms why these particleladen cells are immobilized, viz., one is based on excessive particle-cell, cell-cell chemotactic interactions, and migratory inhibition factors; the other considers the volumetric increase by phagocytized particles, per se, as leading to an inability of the AM to spread and migrate probably through a competitive requirement for surface membrane and cytoskeleton in both endocytotic and migratory functions.

Motor Gasoline Toxicity

The toxicology of motor gasoline is reviewed and the subject considered in two ways. First is as a problem involving a widely used commodity material and the second as a model for the study of complex mixtures. Previously reported subchronic and chronic inhalation studies showing primarily nephrotoxicity in male rats are summarized. Questions of experimental design are discussed including sample verification, species, and dose selection and choice of exposure circumstances. Low boiling, highly branched hydrocarbons primarily in the 6 to 10 carbon number range are implicated. Still unanswered is the basis for the response in male rats only and the precise mechanism of action.

Hydrocarbon Nephropathy in Male Rats: Identification of the Nephrotoxic Components of Unleaded Gasoline

Previous subchronic and/or chronic inhalation studies of unleaded gasoline and a variety of petroleum naphthas, solvents, and distillates have shown that these complex materials are capable of inducing a distinctive nephropathy which appears limited to male rats. Therefore a series of gavage screening studies using male F-344 rats was conducted on components of gasoline to more clearly identify the major contributors to this nephrotoxicity. The dosing regimen consisted of 20 doses administered once daily, 5 days per wk for 4 wk. Tested were 15 pure hydrocarbon compounds typically found in unleaded gasoline boiling range, 4 naphtha streams representative of those commonly used to blend gasolines and 3 distillation fractions covering the less volatile portions of gasoline. The results revealed that the alkane (paraffin) components were primarily responsible for the nephrotoxic activity seen in unleaded gasoline, with a positive structure-activity response relating the degree of alkane branching to the potency of the nephrotoxic response. In addition, the nephrotoxic activity observed with the naphtha streams and distillation fraction correlated well with the proportion of branched alkanes contained in each.

Chronic Inhalation Studies in Mice: I. Facilities and Equipment for “Nose-Only” Exposure to Cigarette Smoke

Abstract Facilities and equipment are described for large-scale, long-term “nose-only” inhalation exposure of mice to whole cigarette smoke. Experimental procedures and equipment were designed to provide the mice with exposure conditions where [1] the lung was the major target organ for the smoke, [2] large quantities of fresh, whole cigarette smoke could be generated, [3] large numbers of animals could be exposed at one time, [4] routine, daily exposures could be given over a major portion of the lifetime of the animal, [5] monitoring and documentation of the quantity of smoke presented to the animals was provided during each exposure session, [6] safety systems were provided that assured exposure of the animals to smoke only under pre-set exposure conditions, and [7] cigarette smoke was generated under conditions where factors, such as cigarette type, smoke aerosol concentration and smoke particle size, were controlled.

Characterization of Diesel Exhaust in a Chronic Inhalation Study

We describe characterization of the exposure atmosphere in a life-span study of rats and mice exposed to chronic inhalation of diluted diesel exhaust. Diesel exhaust was generated by one of two General Motors 1980 Model, 5.7-liter V8 diesel engines connected to an eddy current dynamometer/flywheel system and operated on the Federal Test Procedure urban driving cycle. Animals were exposed 7 hours/day, 5 days/week to exhaust at particle concentrations of approximately 7000, 3500, and 350 µg/m3 or to clean air. Throughout the 24-month study, the mean particle mass concentration remained within 5% of the target values. Measured gas concentrations of CO, CO2, NO, NO2, and hydrocarbons were roughly proportional to the dilution ratio. A combination of a Lovelace Multijet cascade impactor followed by a parallel flow diffusion battery gave mass median diameters of 0.23 to 0.26 µm averaged over complete cycles and geometric standard deviations larger than 4. The aerosol concentration profile was associated with the operating cycle. The measured diesel particle size was similar to previously reported values of particles released to the atmosphere from the same model engine.

Characterization of diesel exhaust in a chronic inhalation study.

We describe characterization of the exposure atmosphere in a life-span study of rats and mice exposed to chronic inhalation of diluted diesel exhaust. Diesel exhaust was generated by one of two General Motors 1980 Model, 5.7-liter V8 diesel engines connected to an eddy current dynamometer/flywheel system and operated on the Federal Test Procedure urban driving cycle. Animals were exposed 7 hours/day, 5 days/week to exhaust at particle concentrations of approximately 7000, 3500, and 350 micrograms/m3 or to clean air. Throughout the 24-month study, the mean particle mass concentration remained within 5% of the target values. Measured gas concentrations of CO, CO2, NO, NO2, and hydrocarbons were roughly proportional to the dilution ratio. A combination of a Lovelace Multijet cascade impactor followed by a parallel flow diffusion battery gave mass median diameters of 0.23 to 0.26 microns averaged over complete cycles and geometric standard deviations larger than 4. The aerosol concentration profile was associated with the operating cycle. The measured diesel particle size was similar to previously reported values of particles released to the atmosphere from the same model engine.

The Effects of Tobacco Modification on the Biological Response to 13-Week Cigarette Smoke Inhalation in Inbred Syrian Hamsters

Twice daily exposure of 12–24 male inbred Syrian BIO 15.16 hamsters for 13 weeks to maximally tolerated doses of smoke from 12 types of investigational cigarettes under experimental conditions and with previously described instrumentation (Bernfeld et al., 1979) resulted in the following response: increased occurrence and aggregation of alveolar macrophages, increased occurrence of tracheal squamous metaplasia, and increased frequency and severity of laryngeal hyperplasia. The statistical significance of these changes was evaluated by means of loglinear models. The effect of varying the nicotine level in tobacco leaf between 0.2 and 1.5% caused no statistically significant changes in the subchronic response. Smoke from Bright tobacco with average tar yields of from 22.4 to 26.2 mg per cigarette caused significantly more alveolar macrophages and laryngeal hyperplasia but less tracheal squamous metaplasia than did smoke from Burley tobacco, with from 9.3 to 10.5 mg tar per cigarette. Deproteinization of tobacco did not change the response of the hamsters to the resulting smoke. Maleic hydrazide-field treatment of tobacco significantly reduced the alveolar macrophages, but spiking of tobacco with maleic hydrazide increased the response. Previous work had suggested that the tumorigenic response to cigarette smoke in chronic inhalation studies in hamsters may be predicted from subchronic inhalation studies in the same animal model (Bernfeld et al., 1983a). The present results then suggest that smoke from low-nicotine cigarettes is not less tumorigenic in the hamster than that from high-nicotine cigarettes, that smoke from high-tar Bright tobacco is more carcinogenic than that from low-tar Burley tobacco, that deproteinization of tobacco does not affect the tumorigenicity of the resulting smoke, and that maleic hydrazide-field treatment of tobacco does not increase the tumorigenicity of the resulting smoke, whereas spiking of tobacco with maleic hydrazide might do so.

A Chronic Inhalation Study with Unleaded Gasoline Vapor

A chronic inhalation study of unleaded gasoline vapor was conducted in mice and rats. The gasoline employed was typical of gasoline used in the US and contained 2% benzene. Groups of both sexes of B6C3F1 mice and Fischer 344 rats were exposed to three concentrations of vapor, 67, 292, and 2056 ppm. Exposures were for 6 hours per day, 5 days per week, for periods ranging from 103 to 113 weeks. Interim sacrifices were conducted at 3, 6, 12, and 18 months. Laboratory studies, including hematological and biochemical determinations, were performed on rats at the interim sacrifices and at termination. Histopathological studies were conducted on both species at every interval. No consistent compound-related changes were seen in pharmacotoxic signs, mortality, hematological, or biochemical indices in either species. Significant depression of body weight gain was seen in both sexes of rats and male mice exposed to the highest level of gasoline vapor. On gross necropsy, a compound-related increase in liver nodules and masses was seen in female mice exposed to the high level. The most interesting observations were made on histopathological examination of the rats' tissues, and, of these, pathological changes in the kidneys were the most striking. Renal carcinomas or sarcomas, in the cortex or near the renal poles, were seen in the male rats at all dose levels, with some evidence of a dose-response relationship. One female rat in the intermediate dose group exhibited a renal sarcoma. Two mice had renal tumors, considered to be spontaneous neoplasms. Mention is made of new studies that have been prompted by the present findings.

Subchronic Cigarette Smoke Inhalation Studies in Inbred Syrian Golden Hamsters That Develop Laryngeal Carcinoma Upon Chronic Exposure<xref ref-type="fn" rid="FN2">2</xref>

Inbred BIO 15.16 Syrian golden hamsters were exposed for 6-20 weeks to smoke from three types of experimental cigarettes. The incidence and severity of laryngeal hyperplasia increased in these hamsters, a few (2) laryngeal papillomas appeared, alveolar macrophages became more frequent and aggregated, and hyperplasia of terminal bronchiolar epithelium occurred. This subchronic response of hamsters to smoke markedly differed for the three types of cigarettes. Statistical evaluation of the data by log linear models proved these differences to be significant. At equal doses of smoke, the most severe response was caused by an all-tobacco cigarette. The weakest subchronic effects, next to those seen in the negative control group, were elicited by smoke from a cellulose-derived tobacco supplement. The effects of smoke from a 1:1 blend of the two smoking materials were intermediate. The severity of the subchronic response of the respiratory tract paralleled the extent of malignant transformations of the larynx previously observed in the same animal model with the same three types of cigarettes in chronic inhalation studies.

7 Final Report on the Safety Assessment of Polyvinylpyrrolidone/Vinyl Acetate Copolymer

Polyvinylpyrrolidone/Vinyl Acetate Copolymer (PVP/VA Copolymer) is the copolymer of vinyl pyrrolidone (VP) and vinyl acetate (VA) monomers. The ingredient is used primarily in hair care products and secondly in skin and nail products. Acute oral toxicity studies on mice and rats showed low to no toxicity. Chronic oral and inhalation studies produced no effects. The acute ocular irritation of PVP/VA Copolymer at concentrations ranging from 25% to 50% in alcohol produced no reaction to severe irritation. Acute skin irritation studies of 50% PVP/VA Copolymer in alcohol on abraded and intact skin produced mild skin irritation. PVP/VA Copolymer was not a sensitizer to guinea pigs after intracutaneous injections. Formulations containing 1.75%, 4.0%, and 5.0% PVP/VA Copolymer produced no irritation in 24-hour clinical patch tests nor any evidence of sensitization in a repeated insult patch test at a concentration of 5.0%. On the basis of the available information, it is concluded that Polyvinylpyrrolidone/Vinyl Acetate Copolymer is safe as a cosmetic ingredient under present conditions of concentration and use.

The effects of lidocaine and hexamethonium on prostaglandin F2‐alpha‐ and histamine‐induced bronchoconstriction in sulfur dioxide‐treated beagle dogs

AbstractThe effects of local deposition of the topical anesthetic lidocaine and of ganglionic blockade by hexamethonium were investigated in pharmacologic bronchoconstriction with sulfer dioxide (SO2)‐induced hyperreactive beagle dogs. Control bronchopulmonary provocations, i.e., increases in pulmonary resistance (RL) and decreases in dynamic lung compliance (CDYN), were accomplished by aerosols of prostaglandin F2‐alpha (PGF2α) and histamine (HIST) after a six‐month chronic inhalation study using 500 ppm SO2. Pretreatment with a lidocaine aerosol (2.0%; 30 breaths) failed to produce any inhibition of bronchospasm induced by aerosols of PGF2α or HIST. An IV infusion of hexamethonium (10.0 mg/kg) significantly inhibited PGF2α‐induced percent changes in both RL (226.4 ± 45.2% vs. 134.7 ± 28.7%) and CDYN (52.6 ± 10.8% vs. 35.9 ± 8.8%) but failed to produce significant inhibition against HIST‐induced bronchospasm. These results suggest that the bronchial hyperreactivity attributed to SO2 exposure in our model is probably due in fact to an increased sensitivity of the afferent portion of the cholinergic pathway due to lidocaine's failure to provide inhibition at this site. No change occurs at the ganglia based on the similar action of hexamethonium in this study as to previously published work.

Chronic inhalation study of mice subjected to diethylhydroxylamine, nitroethane, and diethylamine hydrogen sulfite

Institute of Cancer Research Swiss strain mice were subjected to the inhalation of 10.3 ± 3.7 ppm diethylhydroxylamine, 10.1 ± 4.1 ppm nitroethane, and the vapor of diethylamine hydrogen sulfite for over 2 years. Histopathologic evaluation of all organs indicated only a few significant findings. The incidence of all tumors, as well as subcutaneous tumors (principally fibrosarcomas), increased in exposed males with marginal statistical significance ( P = 0.12 and 0.048, respectively). The incidence of all tumors in exposed females decreased with marked statistical significance ( P < 0.0005).

Carcinogenicity and toxicity of 1,2-dibromoethane in the rat

A chronic inhalation study of ethylene dibromide (EDB) was conducted in Sprague-Dawley rats. Four groups of rats received either control air, 0.05% disulfiram in the diet, 20 ppm of EDB, or 20 ppm of EDB and 0.05% disulfiram in the diet for 18 months. Rats receiving 20 ppm of EDB had high mortality and an increase, compared to controls, in one or both sexes of tumor incidences in the mammary gland, spleen, adrenal, liver, kidney, and subcutaneous tissue. A combined treatment of 20 ppm of EDB and 0.05% disulfiram in the diet resulted in earlier deaths (all within 14 months) and decreases in body weight gain, food consumption, hemoglobin, hematocrit, and RBC counts. This combination of EDB and disulfiram treatment also caused high incidences of tumors in liver, spleen, kidney, adrenal, thyroid, lung, mesentery, and mammary gland in one or both sexes. Testicular atrophy was found in 90% of the male rats that received a combination of EDB and disulfiram treatment.

Studies on the toxicity of allyl chloride

The toxicity of allyl chloride was determined in several species of animals. The oral LD 50 was 425 mg/kg in the mouse and 460 mg/kg in the rat. The 2-hr LC 50's in the mouse, rat, guinea pig, rabbit, and cat were 11.5, 11.4, 5.8, 22.5, and 10.5 mg/kg, respectively. The target organs were the liver, kidneys, and nervous system, and the lungs in the inhalation studies. In the cat, the latent period and motor period of the positive conditioned reflexes were prolonged, and in some cases the reflexes disappeared, but the differentiation reflexes were not affected. In a susceptible cat, the threshold concentration was found to be 100 mg/m 3. In the chronic inhalation studies, the rabbits showed clinical signs of peripheral neuropathy. This was confirmed by electromyographic recordings and microscopic examination. The cat was less susceptible than the rabbit. In addition, there were pathological changes in the liver, kidneys, and lungs in these animals. The peripheral neuropathy reported in this paper and by F. S. He, D. G. Shen, Y. P. Guo and B. Q. Lu ( China Med. J. 93, 177 (1980)), which had not been observed before, confirms the clinical observation made on occupational workers exposed to allyl chloride ( Hyg. Res. 5, 463 (1976)).

Experimental conditions in GMR chronic inhalation studies of diesel exhaust.

A chronic inhalation exposure study was initiated to study the potential health effects of diesel exhaust on laboratory animals. Test atmospheres of clean air (control) or freshly diluted diesel exhaust at nominal particulate concentrations of 250, 750 and 1500 micrograms m-3 were supplied to four large volume inhalation chambers in which individually housed Fischer 344 albino rats (Rattus norvegicus) and Hartley guinea pigs (Cavia porcellus) were exposed for 20 h per day, 51/2 days per week. The diesel aerosol concentration, chamber temperature and relative humidity were continually monitored and controlled to maintain the exposure dose levels and an environment of 22 +/- 2 degrees C and 50 +/- 20% relative humidity. Animals were randomly sampled from the chambers for physiological, biochemical and pathological studies throughout the exposure period. The study was continued without interruption for 24 months with the mean diesel particle mass concentrations within 6% of the target values. The standard deviation of the mass concentration measurements was approximately 30% of the mean.

Chronic inhalation study in rats, using cigarettes containing different amounts of cytrell tobacco supplement

The paper describes a chronic (18-month) inhalation study in rats, comparing respiratory tract lesions produced by exposures to cigaretts with different inclusion of Cytrel®, a tobacco supplement. Histopathological examinations indicated lower responses in animals exposed to Cytrel-containing cigarettes than in those exposed to all-tobacco cigarettes, despite similar total deliveries of smoke. The decrease in response was approximately proportional to the level of Cytrel inclusion.

Introduction to and experimental conditions during the first year of the GMR chronic inhalation studies of diesel exhaust

A chronic exposure study was initiated to determine the effects of diesel exhaust on the health of experimental animals. For this purpose, test atmospheres of clean air (control) or freshly diluted diesel exhaust at concentrations of 250, 750, and 1500 μg/m 3 were supplied to four 12.6 m 3 inhalation chambers which housed rats and guinea pigs. Diesel aerosol size and concentration, as well as chamber temperature and relative humidity, were continually monitored and controlled to maintain the exposure dose levels and an environment of 22±2°C and 50%±20% relative humidity. The concentrations of CO and NO x were found to be 5.8±1.0 mg/m 3 and 7.9±1.0 mg/m 3 above ambient in the chamber containing 1500 μg/m 3 of particulate. Animals were supplied from the chambers, on a random basis, for both intramural and extramural studies throughout the exposure period. The experiment ran uninterrupted for over twelve months with mean diesel particle mass concentrations within 2% of the target values.

NH 3 concentrations in the expired air of the rat: Importance to inhalation toxicology

Endogenously produced ammonia (NH 3) has been quantitated in the expired air of dogs and humans but data for rodents are not available. NH 3 in expired air may have importance in toxicology studies with inhaled gases, vapors, or aerosols because of its ability to form secondary reaction products. Depending upon the reaction product(s) formed, the toxicity of an airborne agent may be increased or decreased. The objective of this study was to quantitate NH 3 in the expired air of unanesthetized Fischer-344 rats, a species commonly used in inhalation toxicity studies. Whole body plethysmography and an indophenol, colorimetric assay were used to quantitate breath NH 3. Concentrations of NH 3 ranged from 10 to 353 ppb ( x = 78 ppb ) in nose-breathing animals and 34 to 744 ppb ( x = 286 ppb ) in tracheal cannulated animals. These differences were attributed to the absorptive effect of the moist, upper respiratory tract in nose-breathers which was absent in animals with tracheal cannulas. These results compared favorably with published reports using larger species. The presence of NH 3 in the expired air of the rat suggests that reaction products may be formed with a variety of airborne chemicals. This may be particularly significant in low-level, chronic inhalation studies.

Experimental data on the neurotoxicity of methyl-ethyl-ketone (MEK)

A severe potentiating effects of methyl-ethyl-ketone (MEK) on the peripheral and central neurotoxicity of n-hexane could be demonstrated in a chronic inhalation study in rats.

Evaluation of the chronic inhalation toxicity of a manganese oxide aerosol--I. Introduction, experimental design, and aerosol generation methods.

A brief literature review on manganese toxicity is presented; as related to designing a chronic inhalation study for evaluating methylcyclopentadienyl manganese tricarbonyl when utilized as a motor fuel additive. The experimental design of this study is described. The generation system utilized to simulate the manganese aerosol produced by an internal combustion engine is described in detail. This generation system operated twenty-four hours per day, seven days per week producing aerosols at 11.6, 112.5, and 1152 micrograms Mn/m3 with an aerodynamic diameter of approximately 0.11 micron.