Yokkaichi asthma (四日市ぜんそく, Yokkaichi zensoku), one of the Four Big Pollution Diseases of Japan, occurred in the city of Yokkaichi in Mie Prefecture, Japan, between 1960 and 1972. The burning of petroleum and crude oil released large quantities of sulfur oxide that caused severe smog, resulting in severe cases of chronic obstructive pulmonary disease, chronic bronchitis, pulmonary emphysema, and bronchial asthma among the local inhabitants. The generally accepted sources of the sulfur oxide pollution were petrochemical processing facilities and refineries that were built in the area between 1957 and 1973.
In 1955, the Ministry of International Trade and Industry began its policy to transition Japan's primary fossil fuel source from coal to petroleum. To accomplish that goal, construction of the Daichi Petrochemical Complex began in 1956. The complex contained an oil refinery, a petrochemical plant, and a power station. This was the first petrochemical complex constructed in Japan.
In 1960, the government of Prime Minister Hayato Ikeda accelerated the growth of petrochemical production as part of its goal to double individual incomes of Japanese citizens over a 10-year period. Also in 1960, MITI announced that a second complex was to be constructed on reclaimed land in northern Yokkaichi. The second complex went online in 1963. As demand for ethylene and other petrochemicals rose, a third complex was constructed which began production in 1972. Yokkaichi transferred its energy production from coal to oil more quickly than the rest of the nation. The oil used in Yokkaichi was primarily imported from the Middle East, which contained 2% sulfur in sulfur containing compounds, resulting in a white-colored smog developing over the city.
Beginning shortly after the opening of the first complex in 1956, severe cases of chronic obstructive pulmonary disease, chronic bronchitis, pulmonary emphysema, and bronchial asthma rose quickly among the local inhabitants. Taller smokestacks were implemented, but these simply spread the pollution over a wider area and did not help alleviate the reported health issues.
A class action court case was brought against Showa Yokkaichi Oil and initially adjudicated in September 1970. The class was ruled to contain 544 individuals, but that number has increased over the ensuing years.
A 2008 study by researchers from the Mie University Graduate School of Medicine and the Hiroshima University Natural Science Center for Basic Research and Development indicated a 10 to 20-fold higher mortality rates as a result of COPD and asthma in the affected populations of Yokkaichi versus the general population of Mie Prefecture.
Initial attempts to alleviate the problem by raising the height of smokestacks to disperse the pollutants over a larger area proved ineffective. Eventually flue-gas desulfurization was implemented on a large scale, leading to an improvement in the health of local populace.
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