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Salient. Newspaper of the Victoria University Students' Association. Vol 42 No. 14. July 2 1979

"The Most Poisonous Synthetic Substance Known"

"The Most Poisonous Synthetic Substance Known"

Small as these quantities may seem, in the world of chemistry they are a part of reality. TCDD-dioxin is roughly 67,000 times more poisonous than cyanide, and 500 times more so than strychnine. This means that one 67, 000th of a gram of TCDD has the same effect as one gram of cyanide.

In fact, TCDD is regarded as the most poisonous synthetic substance known.

Experiments carried out by Professor James R. Allen and associates of the University of Wisconsin in the United States in 1976 showed that TCDD caused significant levels of liver cancer in rats at doses of five parts per billion to five parts per trillion. (This is a figure so small it is preceded by 12 zeroes to the right of the decimal point: 0.000000000005)

2,4,5-T

2,4,5-T

The TCDD-level of 2,4,5-T produced in New Zealand is said to be as far down as 0.01 ppm - that is, eight zeroes to the right of the decimal point. This means that the dioxin level accepted as "safe" in New Zealand remains still several thousand times higher than the smallest dose found to cause cancer in rats.

And, taking into account a World Health Organisation ruling that any dose accepted as safe for humans should be at least 2000 times lower than the lowest dose found to cause cancer in animals, it is hard to see how the present New Zealand level of 0.01 ppm TCDD in 2,4,5-T can, in fact, be regarded as safe.

1 Seveso is everywhere

Birds began to drop off the roofs, dead. Cats died in the streets. Yellow-rimmed holes appeared in the leaves of the plants. When the children came home from play with red skin-rashes, people gradually realised than something was not quite right.

It happened on July 10, 1976. The ICMESA chemical company, situated outside Seveso (Northern Italy), had closed down for the weekend. There was a "runaway reaction" in a vessel producing trichlorophenol (TCP), a substance used in the manufacture of cosmetics. It is also the chemical precursor of 2,4,5-trichlorophenoxy acetic acid - that is, the herbicide 2,4,5-T.

When the pressure had reached the critical limit, it blew the safety valve, releasing a hot purple cloud into the atmosphere. Contained in that cloud were 300 kilograms of trichlorophenol and two kilograms of TCDD (2,3,7,8-tctracholrodibenzo-para-dioxin), a virulent poison.

This fact alone should have been sufficient reason for the ICMESA management to alert the authorities and urge instant, large scale evacuation of the town's inhabitants. Instead, mum was the word. Only when the signs of the catastrophe had become manifest - in all, some 500 people had to be hospitalised, 3000 animals died and 75,000 had to be destroyed - did the company admit that TCDD-dioxin had indeed escaped into the atmosphere. Not until almost three weeks after the explosion was evacuation finally begun. It was this delay which gave most cause for concern, in view of the known toxicity of TCDD.

However, ICMESA's behaviour in the face of trouble was merely a further instance of the almost aggressively defensive stance often characteristic of the industry as a whole. ICMESA, a subsidiary of the Swiss chemical group of companies, Givaudan S.A. (which in turn is a subsidiary of the giant Hoffman-La-Roche pharmaceutical concern in Basle), was chosen as manufacturing site for the highly dangerous production of trichlorophenol because Italian legislation on dangerous chemicals had remained unchanged since '34.

Another reason was that Givaudan itself had suffered adverse publicity in 1972 following the death of more than 30 babies in France. Unwittingly, the mothers had applied a baby-powder (manufactured by Givaudan) which contained a lethal dose of an anti-bacterial agent, hexochlorophene. But instead of adopting a safer manufacturing process for trichlorophenol - from which hexachlorophenc is made - the firm shifted this part of its operation to Italy.......

Certainly no-one at managerial level of the ICMESA - Givaudan-Roche troika could claim ignorance of the dangers involved in TCP-manufacture, More than 20 cases of TCP-accidents, from 1949 onwards have been documented by the International Labour Organisation's International Occupational Safety and Health information Centre in Geneva.

For example, in November 1953 at the West German Badische Anilin und Soda Fabrik (BASF) in Ludwigshafen a smaller-scale Seveso-type accident occured at a TCP-producing plant. On this occasion previously unknown and highly toxic chlorinated hydrocarbons - of which TCDD -dioxin is but one - were chemically identified for the first time.

Fifty-five workers were exposed to the dioxin, and all developed chloracne, a highly disfiguring rash of boils and pimples. Twen-ty-one developed symptoms of systemic poisoning which included damage to the liver, kidney and spleen. The heart, respiratory tract, eyes and nervous system were also affected. BASF medical superintendent Dr A. M. Thiess described the case of "G", one severely affected fitter, thus:

"The nostrils were fissured and looked as if burnt out. The hairy part of the head showed a smudgy discolouration and was infilt-rated with leathery patches. Hairloss was increased. Countless pimples continually became inflamed, forming fingertip-sized abscesses. G. could not sweat and had a feeling of boiling inside his skin."

Ten years later, "G." was hospitalised with edema of the lower leg and bleeding in the lung, and died of these late consequences of TCDD-poisoning.

The plant was closed down. Every few months rabbits would be sent in as "sensors." These tests were continued until 19 68 but the rabbits never survived. That year the factory was dismantled under the most elaborate safety precautions. Parts of the building were packed into airtight containers and buried in disused salt mines. Metallic parts were melted down in industrial blast furnaces. (The task of dismantling and "burning" Seveso and much of its outlying top soil to a depth of at least 10 centimetres remains as yet untackled.)

Other accidents had occured in the United States, the U.K., the USSR, Holland, France, Italy, Czechoslavakia, Austria and elsewhere in West Germany.

The Hamburg firm Boehringer Ingelheim experienced two accidents, then developed its own, safer manufacturing process. It wasn't widely adopted because it was also less profitable. But even New Zealand's 2,4,5-T manufacturer Ivon Watkins-Dow, employing the safer Boehringer process-judging from a fact-sheet put out by IWD; the firm actually refuses to deny or confirm this - has not been without accidents.

In 1975 an explosion, caused by mounting pressure in a chemicals mixing vessel used in the manufacture of a herbicide, released a "big ball of orange flame and dark smoke that went up with a whoosh in a mushroom." (Staff reporter, Taranaki Herald.) However, that explosion had nothing to do with 2,4,5-T production, I was told in a recent personal communication with IWD, "as, in fact, the process was concerned with the manufacture of another pesticide."

This may be so. But shouldn't the public have a right to know, which?

2 TCDD - The on/off poison

Whether a chemical substance is toxic or not depends largely on the type of poison, its molecular structure, the amount of intake per time unit, as well as on the part of the body it first comes into contact with and on the part if affects.

The human body constantly fends off all sorts of alien substances which attempt to gain entry into it. These reaction-patterns are, however, phylogenetically determined, that is to say their main thrust is directed against substances occuring in nature.

This situation has undergone drastic changes since the beginning of industrialisation. An immense number of new chemical substances have entered the environment. Each year hundreds of new chemicals are added to the list. Along with this number of allergenes, (allergy-causing factors), also increases.

Initially, the body will always attempt to rid itself of alien matters through the liver, the body's sewage treatment plant, by breaking down harmful chemical substances to harmless ones. And the skin's glands too, can try a first localised counter-attack. If this doesn't succeed, and if even the liver cannot cope with the poisonous combinations, then, as a rule, these are the organs first to go.

Liver and skin, along with the kidneys whose job is to detoxify the blood, are, therefore, the organs most easily damaged by poisons.

This could be seen, for example, in the children of Seveso who, playing outdoors at the time of the explosion, were exposed to the greatest dosages of the poisonous TCDD-fallout. First they developed a seriously disfiguring kind of acne; later, many of the children also showed signs of liver disorders.

Progress in the field of biochemistry has now made it possible to investigate toxicological processes within the body (or plant) cell itself.

The main attention has been focused on researching enzymatic systems or the development of anti-bodies. The findings from these toxicological studies have made possible a better quantitive assessment of the risk nosed by toxic substances in the environment And it has been shown that the same enzyme systems which are supposed to protect the body, can in fact, participate in the transformation of alien substances into highly toxic metabolites, that is, internally produced poisons, which are of particular relevance in assessing foetus-damaging, cancer-causing and gene-damaging tendencies of environmental pollutants.

One group of chemical compounds subjected to considerable critical flak in recent years are the so-called chlorinated hydro-carbons. In particular, vinylchloride (VC), used for more than four decades to make a popular type of plastic - polyvinylch loride, or PVC - was found, as late as '74, to cause cancer. This finding alarmed scientists and the general public alike and woke them up to the limitations of toxicological checking methods devised to that date.

One West German toxicologist. Professor Dietrich Henschler of Wuerzberg University, expressed concern that similar toxic effects might be detected in other members of this family of chemical compounds. Henschler had discovered a connection between the molecular structure of these compounds and their toxic effects. In some substances he said, the toxicity increased with the number of chlorine atoms in the molecule

The molecule structure can also give hints as to a chemical's cell-damaging and cancer-causing propensities. Chlorinated ethylenes with a symmetrical molecular structure, for example, cause no damage to cells. If, on the other hand, the structure is asymmetrical, as for example in the case of VC, then the substance causes cancer.

But such correlations between molecular structure and toxic effectiveness are not very well understood and continue to baffle scientists. Indeed, the order of number of atoms wither a molecule is by no means a reliable indication of a chemical's toxicity.

In particular the dioxins, including TCDD, show an unusual type of behaviour. The same molecule can be either a super-poison or, comparitively, much more harmless. TCDD is, truly, an on/off poison. And indeed, most researchers of the effects of TCDD wind up with curiously on/off findings. Most, like Professor James Allen of the University of Wisconsin, add that "the elucidation of the molecular mechanism of TCDD toxicity is required for a better understanding of these results."