Long‐term effects of volcanic ash from Mount St. Helens in normal and melanoma‐bearing mice

The toxicity of long‐term exposure to Mount St. Helens volcanic ash was studied in female B6D2F1 mice. The mice, fed diets containing 10% ash, were observed for 43 wk. Exposure had no effect on hematology, plasma amino acid levels, food and water consumption, and urinary and fecal output. Mice fed the ash diet grew at a faster rate than mice maintained on the control diet. This increase was reflected in an increase in carcass and gastrointestinal tract weight. Lactic dehydrogenase was elevated throughout the observation period, but other clinical chemistries were normal. Mice suffered no apparent respiratory problems during the 43‐wk observation period. The ash had mixed effects on survival of B16 melanoma‐bearing mice. Sudden exposure and long‐term exposure (30 and 44 wk) in mice injected with a rapidly growing tumor did not affect survival. In contrast, mice implanted with a slow‐growing tumor at 7 and 15 wk of exposure exhibited decreased survival relative to control mice.