From the UK National Risk Register of Civil Emergencies (2013) regarding an effusive eruptions as is happening now (Not the future suggested caldera collapse of Bardarbunga)
3.35
The research and ongoing modelling have been used to estimate the expected modern-day impacts of a similar event. It is anticipated that an eruption of this scale and type could have significant public health impacts on the ground. Similarly, the aviation industry and aircraft passengers could be affected because at this height sulphur dioxide concentrations could be even greater than at the ground. However, a quantitative assessment is required to fully characterise the risks. Widespread airspace closures on a significantly bigger and more prolonged scale than those experienced in April 2010 could be expected due to the longevity of such an eruption.