Cause of Death Environmental Exposure--adverse effects Eye Diseases--etiology Health Status History, 15th Century History, 17th Century History, 18th Century History, 19th Century History, 20th Century History, 21st Century History, Medieval Humans Iceland Particle Size Particulate Matter--adverse effects Respiratory Tract Diseases--etiology Risk Assessment Risk Factors Skin Diseases--etiology Time Factors Volcanic Eruptions--adverse effects