The South Gyeongsang Province was one of the areas identified for industrial development along with the independently administered coastal corridor between Ulsan and Busan.
From 1974 onwards, an area of 2,000 ha in Onsan - to the south of Ulsan - became home to a multitude of industrial complexes, with 12 chemical factories initially in operation.
After the government ran blood and urine tests, an official statement pushed back on the theory of poisoning.
[3] The collective group of symptoms was termed Onsan illness as a root cause was initially unknown and later thought to be cadmium poisoning.
[3] The health impact combined with the risk to their livelihoods sparked a grass roots movement supported by the media.