Dioxin Levels in Wastes

There is a common mis-understanding, because dioxins and furans are found in parts per million (ppm), parts per billion (ppb) or parts per trillion (ppt) levels in Midland soils and in river sediments,  that dioxin concentrations in wastes or products must also be at these levels.

While some products may have had ppm or ppt levels of dioxins, other wastes, especially those dumped into Dow's chemical waste ponds or incinerated in Dow's early tar burners, may have had much higher levels, up to percent levels of dioxins

During the demolition of the Ronnel Insecticide Plant that operated in the Midland plant from 1955 to 1977, a black tarry substance was found when some equipment was dismantled.  The equipment had been used to scrub 2,4,5-trichlorophenol vapors that were released when off-loading railcars of the raw material.  When the last railcar was unloaded, the equipment was not shut down properly and a mixture of trichlorophenol and liquid caustic continued to be held at a temperature of 250°F for three to four years.

When the tars were analyzed by Dow's Analytical Laboratory, the wastes were determined to contain 26% TCDD. 

If percentage levels of TCDD could be formed at a temperature of 250°F (the temperature of 15 psig steam tracing), it is possible that similar levels could be formed in a much shorter time at the higher reaction temperatures that were routinely used to manufacture chlorophenols.

There is also some information that suggests that dioxins and furans could have been formed in the chemical waste ponds during the summertime.

Dow reported that, in 1933,  the Midland plant synthesized a mass of tars that were buried and then dug up and re-buried three times over the next 25 years.  For the tars to be re-located after burial, Dow must have identified each burial location through surveying and subsequent identification on plant maps. 

During the 25 years of excavation and reburial, the Midland plant had a number of disposal options -- a tar burner, a rotary kiln, the 1925 Landfill, Poseyville Landfill and various ponds that were being filled in.  It's interesting to speculate as to why Dow did not lose track of the these wastes and, yet, did not dispose of them.

Perhaps, the tars were so toxic that plant management did not wish to incinerate them in the early burners knowing that a certain amount of the tars would not be incinerated but would spread downwind as black smoke. 

Perhaps the tars were so toxic that Dow management did not wish to lose track of the burial locations and run the risk that they could be uncovered accidentally during excavations and come in contact with workers.

It is hard to imagine that a waste could be so toxic that these extraordinary procedures were followed for 25 years.  It is pure speculation, but it is possible that Dow synthesized and purified distillation tar bottoms to determine if the chemicals had any commercial value.   Upon learning that the materials were extremely toxic, Dow surely would have discontinued product development.  A problem of how to dispose of them... perhaps, burial in well identified locations.

Perhaps these chemicals, that were too toxic for disposal, would later be identified as dioxins and furans.  Perhaps, the material that could not be forgotten, even when buried, was purified TCDD.

One interesting question still remains.... what happened to the tars after 1958?  Perhaps, a reader will come forward and answer this question.

A Dow epidemiology study indicated that unpurified 2,4,5-trichlorophenol produced in 804 Bldg. contained approximately 1800 ppm TCDD.  Assuming that a 2% yield lost occurred in the distillation equipment used to purify the products, it is calculated that the waste tar stream from the re-boilers of the distillation column may have contained as much as 9% TCDD.

In 1976, a chemical plant in Seveso, Italy had a chemical release of unpurified trichlorophenol that was manufactured by the same chemistry that Dow used in the 804 Bldg process.  The accidental release caused 447 cases of acute chemical burns and 193 cases of chloracne.  As a precaution to avoid further TCDD exposure to the residents, a total of 77,000 animals were destroyed and buried.

Based on information that was gathered following the accident, the concentration of TCDD that was released was calculated to be approximately 6700 ppm TCDD.  Using the same 2% yield loss that was used in the 804 Bldg. calculation, the TCDD content of distillation column "bottoms" could have been as high as 31% TCDD.  The 31% dioxin level is not TEQ (equivalent TCDD), it is 31% actual TCDD.

When "test burns" of Dow's new 32 Bldg. Incinerator are carried out, it is doubtful is test wastes will contain 31% TCDD or even 9% TCDD.  It is possible that the incinerator may not even be tested to determine the destruction efficiency when incinerating TCDD contaminated wastes.

However, it is probably a safe assumption that even a modern, state-of-the-art incinerator might have difficulty safely incinerating percent levels of dioxins.

As the section of incineration will show,  Dow's early tar burners and incinerators were probably more dioxin vaporizers and dioxin generators than they were incinerators that achieved a very high level of destruction efficiency.  The proof of this statement can be found in the high levels of dioxins still being found in Midland soils more than sixty years after the first Dow tar burner was put into operation.

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