Abstract

The effects of Mount St. Helens volcanic ash, a sandy loam soil, and quartz particles on the lung and mediastinal lymph nodes of Fischer rats were studied at time intervals of up to 109 days after intratracheal instillation of 40 mg ash, soil, or quartz in a single dose or after multiple doses of ash instilled in seven consecutive weekly doses for a total deposition of 77 mg. Quartz caused early granuloma formation, later fibroplasia and collagen deposition, and widespread lipoproteinosis in the lung; severe fibrosis was also seen in lymph nodes. Volcanic ash caused an ill-defined inflammatory reaction with a few rats showing granuloma formation, a very limited linear fibrosis, and a moderate lipoproteinosis, and lymph nodes were enlarged with numerous microgranulomas but without reticulin and collagen formation. Pulmonary reactions to soil particles were less intense but similar to those in ash-exposed animals; lymph nodes were not enlarged. No significant clearance of ash was found at 3 months after instillation. Volcanic ash produced a simple pneumoconiosis similar to what has been described for animals and humans living for prolonged periods of time in dusty desert areas of the United States.

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