Lung changes in rats following inhalation exposure to volcanic ash for two years

Abstract

Rats were exposed by inhalation to 5 or 50 mg/m 3 Mount St. Helens volcanic ash, to 50 mg/m 3 quartz (positive controls), or to filtered room air (sham-exposed controls), for 6 hr/ day, 5 days/week, for up to 24 months to investigate biological effects of chronic inhalation exposure to volcanic ash under controlled laboratory conditions. Exposure-related lung changes comprised accelerated respiratory frequency; alveolar macrophage accumulation; interstitial reaction; lymphoreticular reaction in peribronchiolar regions and in mediastinal lymph nodes; alveolar proteinosis in the 50-mg/m 3 ash-or quartz-exposed groups; increase in fresh lung weights; decreased body weight and increased mortality in the quartz-exposed group; and epidermoid carcinomas especially in the quartz-exposed females and, to a lesser extent, in the 50-mg/m 3 ash-exposed females. The observed changes reflect significant dose-response and agent-response relationships. © 1986 Academic Press, Inc. It soon became apparent that acute effects in healthy persons were minor and temporary (Johnson et al., 1982; Washington State Health Services Division, 1980). However, the effects of chronic exposure to volcanic ash--as experienced, for example, by loggers in the fallout area--were unknown. This uncertainty emphasized the necessity for evaluating the health hazards of chronic ash inhalation in a suitable animal model under controlled laboratory conditions. The results of our study exceed regional relevance and will be of interest to medical personnel and health authorities in nations experiencing volcanic activity, such as the Pacific rim countries which form "the ring of fire." The objectives of our study were to determine whether chronic inhalation of volcanic ash causes lung changes; type and degree of lung changes as a function of ash aerosol concentration and cumulative exposure time; and regression of ash-induced lung changes as a function of aerosol concentration, cumulative exposure, and recuperation time. INTRODUCTION MATERIALS AND METHODS Volcanic AshMount St. Helens volcanic ash was collected at three undisturbed sites in Yakima, Ritzville, and Spokane in the State of Washington, 5 weeks after the May 18, 1980, eruption. These sites represented major population centers in the areas of heaviest ash deposition. The ash samples were oven-dried at 100 _+ 5°C, passed through a No.20 (850-txm) sieve to remove foreign materials, thoroughly mixed in a V-blender, and sterilized by heating in ceramic dishes in an oven at 130°C for 16 hr. After cooling to room temperature, the ash was sealed in polyethylene bags and stored in 5-gal paint buckets for the animal exposures. Ash samples of respirable size, analyzed in our laboratory, contained from 3 to 4% free crystalline silica. Slightly more than half this quantity was quartz and most of the remainder was cristobalite.Min-U-sil (5 fxm) was obtained from Pennsylvania Glass Sand Corporation for exposing a positive-control group to a-quartz, a known potent cytotoxic agent. Aerosol Generation and Characteri...

The respiratory health hazards of volcanic ash: a review for volcanic risk mitigation

“…One study did not find the ash to be toxic (Raub et al 1985). Of the four inhalation studies, the outcome in two was the development of fibrosis (Martin et al 1983a;Wehner et al 1986), but there was no evidence of toxicity in two studies (Raub et al 1985;Wiester et al 1985). Sanders et al (1982) and Vallyathan et al (1983a) studied animals for 400 days and 6 months, respectively, thereby allowing the analysis of the long-term effect of volcanic ash in the lung.…”

“…The inhalation studies which found fibrosis and lesions (Martin et al 1983a;Wehner et al 1986) did so after administering very high doses of ash (50-100 mg m −3 ) over long time periods. The two studies which did not observe toxicity both used lower doses (≤10 mg m −3 ) and had a shorter follow-up.…”

Current Perspectives on Particulate Induced Pulmonary Tumours

“…Similar observations have been reported with other materials, including volcanic ash. 13 Microscopically, these foci represent not only aggregates of dust or dust containing cells but in most instances the additional biological response of the lung to the persistent presence of particles, as described later. The latter inhibits further the clearance of particles from the lung.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] administration ' 9,20 produced similar results. Interestingly, the test materials ranged from crystalline silica,8.10-13 accepted as biologically reactive, to titanium dioxide,14 generally considered to be biologically inert and indeed used frequently in experimental studies as an inert negative control dust.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] In most cases tumours were seen only after a minimum of 12 months exposure. Test materials, exposure regimens and tumour incidences are shown in Table 1.…”