Inhalation studies of Mt. St. Helens volcanic ash in animals. III. Host defense mechanisms

The effects of inhalation exposure of mice or rats to 9.4 mg/m3 volcanic ash, 2.5 mg/m3 SO2, or both on host defense mechanisms were assessed. Cytologic changes in pulmonary lavage fluid included an increase in percentage polymorphonuclear leukocytes due to SO2 exposure and an increase in eosinophils due to ash. SO2 and ash also produced decreases in percentage alveolar macrophages. In the case of ash-exposed animals, this decrease was offset by an increase in lymphocytes. Total cell counts and viability were not affected by any of the exposures. Pulmonary clearance mechanisms were affected in that there were both decreased alveolar macrophage phagocytic capability following ash and ash + SO2 exposures and depressed ciliary beat frequency attributable to ash exposure. None of the inhalation exposures caused increases in susceptibility to an immediate or 24 hr postexposure aerosol challenge with Streptococcus. However, intratracheal instillation of both fine- and coarse-mode volcanic ash caused slight but significant increases in mortality due to bacterial challenge 24 hr after the instillation. The phytohemagglutinin-induced blastogenic response of splenic lymphocytes from exposed animals did not differ significantly from that of control lymphocytes, although the lipopolysaccharide-induced blastogenic response was enhanced. Ash exposure had no effect on susceptibility to murine cytomegalovirus. In summary, volcanic ash alone or in combination with SO2 had only minimal effects on certain host defense mechanisms.     

Inhalation studies of Mt. St. Helens volcanic ash in animals. I. Introduction and exposure system

Due to the lack of information on the effects of inhaled Mt. St. Helens volcanic ash and its potential interaction with sulfur dioxide (SO2), animal studies were performed to determine the acute and chronic health effects of a short-term exposure. This paper describes the inhalation exposure system designed for these studies and theoretically compares the pulmonary deposition in the rats to that in humans. Considering the similarities and differences in regional pulmonary deposition in humans and animals, inhalation studies were performed with fine-mode (less than 2.5 micron aerodynamic diameter, Dae) ash. Comparisons to coarse-mode (greater than 2.5 micron Dae) ash were made using intratracheal instillation. A whole-body exposure system was designed to provide inhalation exposures of animals to Mt. St. Helens volcanic ash, SO2, or a combination of both. All exposures were conducted using fine-mode ash samples generated by a Wright dust feed mechanism at a mean concentration of 9.4 mg/m3 +/- 1.0 SD. Sulfur dioxide was maintained at 2.5 mg/m3 +/- 0.13 SD. Scanning electron microscopy, X-ray diffraction, and X-ray fluorescence were used to characterize the ash.     

Inhalation studies of Mt. St. Helens volcanic ash in animals. II. Lung function, biochemistry, and histology

Rats were exposed by inhalation to 9.4 mg/m3 size-fractionated volcanic ash for 5 days (2 hr/day) and examined for changes in pulmonary function and histology for periods of up to 1 year. Fine-mode volcanic ash, SO2, and a combination of ash and SO2 produced no observable effects in normal rats and rats with elastase-induced emphysema. However, there was a mild irritant response to SO2 which was not influenced by the volcanic ash. Rats injected intratracheally with fine-mode volcanic ash or saline showed no evidence of pulmonary alterations after 6 months. Those injected with coarse-mode volcanic ash showed minor pulmonary functional changes, histologically detectable alveolitis, and small increases in lung weight. In contrast, quartz-injected rats showed large alterations in pulmonary function, lung weight, hydroxyproline levels, and large areas of lung consolidation and fibrosis.     

Inhalation studies of Mt. St. Helens volcanic ash in animals: respiratory mechanics, airway reactivity and deposition

Effects of fine volcanic ash aerosol on pulmonary mechanical properties of awake guinea pigs were evaluated during exposure by inhalation. Ash penetration into the lung as well as tissue response to ash were determined by transmission electron microscopy. The reactivity of airway epithelial irritant receptors following ash exposure was assessed using a histamine bronchoprovocation test. Results indicated that breathing 9,4 mg/m3 of ash for 2 hr did not cause a measurable change in pulmonary function of guinea pigs. Electron micrographs showed that ash particles in the lung below the hilus did not seem to produce any acute tissue reaction and were almost all phagocytized by macrophages. Airways of guinea pigs exposed to ash were significantly less responsive to histamine than were the airways of animals exposed only to air. It appears that even though Mt. St. Helens ash was well tolerated by the guinea pig during the exposure, its presence in the inhaled air did change the "histamine sensitivity" of airway epithelial irritant receptors.     

St. Francis Center

The St. Francis Center in Washington, DC was founded in 1975 to provide support and guidance for individuals and organizations facing life-threatening illness and bereavement. The Center began seeing clients who were living with AIDS since 1983, and has expanded all of its services to include components specifically designed for people living with AIDS and organizations serving people with AIDS. This article describes the orgins of the Center and reveals how the organization grew to meet the challenges of AIDS. The Center can be seen as an organizational model for other pre-existing institutions. Brief case studies demonstrate the activities and techniques of the Center's counseling, training and volunteer support programs as they help people with AIDS, their families and service organizations.