Journal of toxicology and environmental health
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J Toxicol Environ Health · Jan 1986
Nitrogen dioxide exposure and development of pulmonary emphysema.
This study assessed the relationship between nitrogen dioxide inhalation and the development of pulmonary emphysema and investigated how the severity of preexisting emphysema brought about by protease (elastase) instillation into the lung may be augmented by a subchronic exposure to a relatively high concentration of nitrogen dioxide. Lungs of adult Fischer-344 rats were evaluated for emphysematous changes after (1) a single intratracheal instillation of elastase (E), (2) a 25-d exposure to 35 ppm nitrogen dioxide (NO2), and (3) elastase instillation followed by 25-d exposure to 35 ppm NO2 (E + NO2). Rats instilled with sterile normal saline and subsequently exposed to filtered air served as a control group (NS). ⋯ The mean linear intercept values (MLI) obtained with the NS and NO2 exposed lungs were essentially identical with average values of approximately 62 micron. This morphometric parameter was substantially increased in the E- and E + NO2-exposed lungs; no significant differences, however, were found between the MLI values obtained with the E and E + NO2 lungs (approximately 95 and approximately 97 micron, respectively). From these data, as well as histologic examinations of lung sections for evidence of emphysema, we conclude that (1) a subchronic, moderately high level of NO2 exposure does not produce an irreversible emphysematous lesion in the rat model and (2) exposure of rats to 35 ppm for 25 d after elastase instillation into the lungs does not potentiate protease-induced emphysema or bring about a progression in preexisting emphysema.
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J Toxicol Environ Health · Jan 1984
ReviewThe health implications of increased manganese in the environment resulting from the combustion of fuel additives: a review of the literature.
Methylcyclopentadienyl manganese tricarbonyl (MMT) is effective in raising the octane level of gasoline and is currently used in Canada for that purpose in a maximal concentration of 18 mg Mn/l (slightly less than 0.07 g Mn/U. S. gal). It has been estimated that if MMT were used in all U. ⋯ Monkeys exposed to 5000 microgram Mn/m3 also showed no symptoms. There is thus a wide margin of safety between the intakes of Mn essential to health and the high concentrations that have been associated with toxic effects. The small amounts of manganese added to the environment by the combustion of MMT used as a fuel additive would be comparable to the normal background and should not create health problems.
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J Toxicol Environ Health · Oct 1983
Polychlorinated biphenyls (PCBs): dermal absorption, systemic elimination, and dermal wash efficiency.
The objectives of this study were to determine the dermal absorption, systemic elimination, and dermal wash efficiency for polychlorinated biphenyls (PCBs). 14C-Labeled 42% PCB and 14C-labeled 54% PCB were topically and parenterally administered to rhesus monkeys and guinea pigs. Dermal absorption, determined by 14C urinary excretion, was extensive. In guinea pigs, 33% of the applied 14C-labeled 42% PCB dose and 56% of the 14C-labeled 54% PCB dose were absorbed. ⋯ Only 50-65% of an intramuscular dose could be accounted for in urine and feces for up to 28 d excretion. The elimination half-lives following topical administration were not much greater than that following intramuscular administration. This suggests that PCBs are rapidly and extensively absorbed through the skin, and that they are then probably generally distributed throughout the body, and then slowly eliminated.
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J Toxicol Environ Health · Aug 1983
Deposition of sulfuric acid mist in the respiratory tracts of guinea pigs and rats.
Radiolabeled sulfuric acid mists in the size range of 0.4-1.2 micron mass median aerodynamic diameter (MMAD) were generated at 20 and 80% relative humidity at concentrations from 1.3 to 20 micrograms/l. Guinea pigs and rats were exposed to these aerosols by the nose-only route for short periods (30 s) and were quickly sacrificed and dissected. ⋯ A comparison of the data obtained in these studies with those from earlier studies indicates that the deposition of sulfuric acid in the respiratory tract of rats is greater than for nonhygroscopic aerosols having similar MMADs. This may be due to the growth of the droplets in the high humidity of the respiratory tract.
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J Toxicol Environ Health · Aug 1983
Physiological and histological alterations in the bronchial mucociliary clearance system of rabbits following intermittent oral or nasal inhalation of sulfuric acid mist.
Rabbits were exposed to submicometer sulfuric acid mist (H2SO4) for 1 h/d, 5 d/w for 4 wk, during which time mucociliary clearance was monitored by external in vivo measurements of tagged tracer aerosol retention. One group was exposed orally to 250 micrograms/m3, another to the same concentration via the nose, and a third to 500 micrograms/m3 also via nasal breathing. Clearance was accelerated on specific individual days during the course of the acid exposures, especially at 500 micrograms/m3. ⋯ The only change in the rabbits exposed nasally at 250 micrograms/m3 was a significant increase in the number of airways with epithelial secretory cells in the smallest airway classification. The histological alterations provide a basis for observed changes in clearance, and are similar to those found in chronic bronchitis in humans and experimental animals. Differences in site and degree of histological response and degree of physiological change between the two groups exposed to identical acid concentrations appear to have been due to differences in exposure mode, with resultant effects on breathing pattern, aerosol size distribution, and concentration penetrating beyond the upper respiratory tract to specific lung sites.