Arak (Persian: اراک, Arāk; IPA), also known as Soltan Abad (سلطان آباد, Soltān Ābād), is the capital of Markazi Province, Iran. At the 2011 census, its population was 526,182, in 160,761 families. A major industrial city, Arak hosts several industrial factories inside and within few kilometers outside of the city, including the factory of Machine Sazi Arak and the Iranian Aluminium Company. These factories produce nearly half of the needs of the country in steel, petrochemical, and locomotive industries. As an industrial city in a developing country, Arak is subject to the issue of air pollution.