NEPACCO leased plant space from Hoffman-Taff (now Syntex Agribusiness, Inc.) in Verona, Missouri in 1969. Two years thereafter, NEPACCO produced 2, 4, 5-trichlorophenol (TCP) to make hexachlorophene, an anti-bacterial agent. Dioxin is removed from TCP in the filtration and distillation processes, creating what is called “still bottoms”. Production ceased in 1972 when the Food and Drug Administration banned the commercial sale of hexachlorophene.

In 1970, NEPACCO shipped part of the still bottoms to Baton Rouge, Louisiana for incineration. NEPACCO also contacted the IPC, of St. Louis, Missouri for chemical recycling references for possible deposition of the remaining wastes. The Bliss Waste Oil Company, Ellisville, Missouri, owned by Russell Bliss, was subsequently subcontracted with by IPC to haul wastes for NEPACCO. Mr. Bliss and employees began removing the still bottoms from the Syntex property in 1971. Approximately 18,500 gallons of material was hauled by the Bliss company. Dioxin concentrations ranged from 350,000 ppb (parts per billion) to 2,000,000 ppb. The toxicant was mixed with waste oil in storage tanks in Frontenac, Missouri, and applied as a dust suppressant on horse arenas, parking lots, truck lots, and city and county roads in the St. Louis area.

The dioxin contamination was discovered in August, 1971, when a child, who had been playing in a horse arena, became ill and was hospitalized. Numerous horses and other domestic and wild animals using the arena became sick and died after application of the dust suppressant by the Bliss Waste Oil Company. The U.S. Centers for Disease Control and Missouri Department of Health & Senior Services investigated and sampled the arena. It was not until 1974 that TCDD was determined to be the cause of the health problems. The origin of the dioxin was traced back to the plant in Verona, Missouri.