Montserrat's volcanic ash, which blankets a large part of this Caribbean island, may pose a local health threat according to researchers from the University of Cambridge who publish their findings in the journal Science. The Soufriere Hills volcano has ejected large plumes of the ash since 1995, causing a partial evacuation of the island. The material contains very small grains of the silica mineral cristobalite, which if inhaled over long periods, can cause the lung disease silicosis. Because the disease develops after long term exposure it remains unclear what impact the exposures at Montserrat might have.