Dioxins Are Us

The main dioxin-cotaminated active component of Agent Orange, 2,4,5-trichlorophenoxyacetic acid, was manufactured in Czechoslovakia from 1965 to 1968, for US military use, and supplied directly to South Vietnam. There were other suppliers but the Czech-made 2,4,5-T was the cheapest- and it also had an exceptionally high dioxin content.

Spolana Neratovice is a large organochlorine plant that manufactures bulk chemicals and vinyl plastics. For a long time it also served as the main producer of insecticides in the Eastern Bloc. A popular insecticide  hexachlorocyclohexane is made by photochlorination of benzene; HCH has several stereoisomers and only one of them, gamma-HCH aka Lindane, has the useful activity/toxicity profile – the undesired isomers are removed by crystallization. As the purified Lindane constitutes only a fraction of the crude chlorinated mixture, the Lindane manufacture generates a huge waste stream. The chemists in Neratovice were offered bonuses and other incentives to find ways of using the HCH waste for anything of value. One solution of the problem was to treat the undesired HCH isomers with alkali at high temperatures to bring about elimination+hydrolysis. This was done chiefly because one of the products, 2,4,5-trichlorophenol, was the key intermediate for production of a potent herbicide used in agriculture, 2,4,5-T. And  suddenly there was a growing demand for 2,4,5-T and the Czechs were eager to earn some hard currency…

2,4,5-trichlorophenol when heated under strongly basic conditions readily cyclizes to TCDD – the most dangerous dioxin, as we know now. But at the time, long before Seveso and Yuschenko, dioxin formation was considered just a nuisance -one of many yield/purity-affecting side-reactions. (The US military was not picky about the product purity.) 

The communist government of Czechoslovakia never acknowledged its part in the dioxin disaster –  we were told that Agent Orange was an especially terrible poison invented by the imperialists… There has been a substantial direct economic aid to Vietnam over many years though, this included also visitor-worker jobs and student visas (so there is now a substantial Vietnamese community in the cities). I wondered why Vietnam was the recipient of Czech help – but not Cuba, Angola, Syria, North Korea or any other friendly totalitarian regime. Now I think it was quite likely the bad conscience about the Spolana war legacy – and that’s how we got our great & fun-loving Vietnamese students in the Charles Uni organic chemistry class.

Credit: Drugs and Poisons for bringing up the subject of the Rainbow Herbicides

Addendum: A massive Seveso-like poisoning of about 60 workers from 2,4,5-T reactor explosion in Spolana in 1968 ended the production of this material there. The Spolana plant used to have a huge site contaminatition problem; some dioxin-and-mercury buildings were closed off but the cleanup got undeway only after the summer of 2002 when a record flood washed everything into Elbe river. The rising water in 2002 floods also lifted the massive storage tanks for liquified chlorine.  The connecting pipes tore off and about 100 tons of chlorine got out. The yellow cloud fortunately missed the nearby towns. (The slow rate of the underwater release also helped.) The typical inventory at the plant used to be 1000 tonns of liquified chlorine. The main process using chlorine – vinyl chloride production – was taken down some time before the flood because the hydrocarbon cracking unit that provided ethylene for the process blew up. Workers ignited heating gas in the furnaces – a gas that was already mixed with air – and they landed away in some distance but alive. To repair the damage the production got delayed and the electrolysis was halted also. And so by enormous luck the chlorine tanks stood near-empty when the flood ripped them from the pipes.