Fresh volcanic ash is gritty, abrasive, sometimes corrosive, and always unpleasant. Although ash is not highly toxic, it can trouble infants, the elderly and those with respiratory ailments. Small ash particles can abrade the front of the eye under windy and ashy conditions. Ash abrades and jams machinery. It contaminates and clogs ventilation, water supplies and drains.
Power often goes out during and after ashfall.
Long-term exposure to wet ash can corrode metal. Ash accumulates like heavy snowfall, but doesn't melt. The weight of ash can cause roofs to collapse. Wet ash is slippery. Ash resuspended by wind, and human activity can disrupt lives for months after an eruption.