Yokkaichi asthma (四日市ぜんそく, Yokkaichi zensoku) refers to cases of chronic obstructive pulmonary disease, chronic bronchitis, pulmonary emphysema, and bronchial asthma in humans and various environmental changes usually attributed to sulfur dioxide (SO2) emissions which appeared as smog over the city of Yokkaichi in Mie Prefecture, Japan between 1960 and 1972, though other SOx compounds have been proposed. The generally accepted source of the sulfur oxide pollution was the Yokkaichi Kombinato petrochemical processing facilities and refineries built in Yokkaichi between 1959 and 1972 which did not properly desulfurize the high sulfur content in its crude oil. Yokkaichi asthma is considered one of the Four Big Pollution Diseases of Japan and was the subject of Japan's first court case related to pollution.[1][2][3]