This is a continuing series which began here
Scientist at CDC, with few clues to go, took until 1974 to identify dioxin as the toxin in the oil. By this time Bliss had sprayed oil over as many as 150 sites in eastern Missouri including over a quarter of a million gallons of tainted oil on the streets of Times Beach. The search for these contaminated sites, though, did not begin immediately. At the Verona plant, which had since changed hands, investigators found a storage tank containing waste oil 100 times more contaminated than Bliss's oil. This became the primary concern because its potential for human health injury was highest. At their own expense, the new owners had the wastes detoxified.  And with no further reports of serious illnesses, the dioxin issue faded.
It was believed in the 1970's that dioxin decomposed rapidly in soil. Acting on an anonymous tip in 1979, EPA investigators found a number of dioxin contaminated drums near a Verona plant which had lain buried for over six years. Waste leakage from the drums still had high concentrations of dioxin when almost all of it should have decomposed. This got officials to thinking about what had happened to the contaminated soil which had been removed from the horse arenas. After three years of record searching, EPA officials learned that some of the landfill had been used as fill dirt for residential construction. Analysts collected soil samples at the original sites, at the landfill and at the residential sites. Testing by CDC began in the spring of 1982, and the first data released in August showed that dioxin levels had not diminished.  These findings prompted more exhaustive sampling by the EPA of all areas known to have been sprayed by Bliss, including Times Beach.
 At this time no federal guidelines existed for the clean-up of such waste sites. Superfund, the abandoned waste site clean up law, didn't go into effect until 1981.
 Janice Long, David J. Hanson, "Dioxin issue focuses on three major controversies in the U.S." Chemical and Engineering News, 6 June, 1983, p. 23. Up until this time, all attention and concern was focused on the original sites and the residential sites, the so-called Minker/Stout sites named after two families owning homes there.