The exact composition of the Icelandic volcano plume is not known precisely ; "the pollutants of greatest concern to human health in plumes from volcanoes are normally mineral particulates, sulphur dioxide (SO2), fluoridic acids and hydrochloric acid".
Forecasts predict the volcano plume should disperse as on the map below :
Maps & quotes from the National Environmental Research Institute Aarhus University <<<
a plume of dust, smoke,... = a tall, thin mass of smoke, dust or similar
substance, that rises up into the air