Toxicity of volcanic ash from Montserrat

Abstract

The Soufrière Hills volcano on the Caribbean island of Montserrat has been erupting intermittently since July 1995 producing widespread deposition of volcanic ash on the island, and leading to concern as to the health effects of the inhaled ash. This study examined the toxicity of a sample of the ash using a variety of methods. The most important test involved the exposure of rats by inhalation to clouds of the ash, in parallel with similar exposure of another group of rats to a benchmark low toxicity control dust, titanium dioxide. The inhalation exposures were for 6 hours per day, 5 days per week, and for periods of 2, 4, 6 and 8 weeks at concentrations calculated to produce similar lung burdens for the two dusts and high enough to produce inflammation with a low toxicity dust. This comparison showed that the ash produced more inflammation in the lungs than the low toxicity dust. The ash also produced the earliest signs of fibrosis. Comparison with results from previous inhalation studies on quartz (a very toxic dust) and dust from two coalmines showed that the volcanic ash was much less toxic than the quartz, and was close in toxicity to the coalmine dusts. The study also included other toxicity tests, using either cells in bench top tests, or dust injected into the lungs of rats. These tests confirmed that the ash was less toxic than quartz dusts. They also showed some variation in toxicity between samples of ash. However, they produced only limited and less reliable indications of the difference between the effects of the ash those of the low toxicity control dusts. The report recommends that existing data sets on the effects of coalmine dust in miners would be valuable in assessing the risks to the people exposed to the Montserrat volcanic ash.