Iranian authorities ordered schools and offices closed in seven western provinces on Tuesday as a dust storm swept in from neighbouring Iraq, with around 13 million people told to stay indoors. Khuzestan, Kermanshah, Ilam, and Kurdistan provinces were all affected, and state television cited local officials as blaming the closures on high levels of accumulated dust. Govt and private offices also shut in several provinces, including Kermanshah and Ilam, as well as Khuzestan in the southwest. Zanjan in the northeast and Bushehr in the south were also hit. Bushehr, nearly 1,100 kilometres (680 miles) south of Tehran, was given an Air Quality Index of 108 on Tuesday, rated “poor for sensitive groups”. That figure is more than four times higher than the concentration of air microparticles deemed acceptable by the WHO. Iran’s meteorological authorities said the conditions were caused by “the movement of a large mass of dust from Iraq towards western Iran”.