In 1985, EPA found that dioxin was the most potent carcinogen yet tested.

Greenpeace report 'Achieving Zero Dioxin' - July 1994 [1].



Parts of this page


The exaggeration of Greenpeace

Greenpeace is completely outdated about the carcinogenic effect of dioxins. At this moment the class of nitro-PAH's (nitrated polycyclic aromatic hydrocarbons) are found to be the most potent carcinogens [5].
Some toxic chemicals do have equal effects on different animals at nearly the same concentration. This is not the case for dioxins. Dioxins are extremely toxic for Guinea pigs, but a thousand times less toxic for other animals. Humans seems to be much more resistent to the toxicological and carcinogenic properties of dioxins.
Since the accident in Seveso, Italy, where a chemical reactor overheated and a cloud of reaction products, including a few hundred grams of the most toxic dioxin, was emitted over the neighbourhood, this is for Greenpeace the symbol of what can go wrong in a chemical factory. Of course, this was a serious incident, and incidents of that kind should be avoided with all means possible.
A lot of animals, especially grasseaters, died within a few days to a few weeks, but no human died! The only people killed, were the director of the factory, murdered by the Red Brigades and under the panic of that moment, 17 abortions, from which the foetuses were investigated and from which no aberration, related to the accident, was found. There was a lot of people affected by a skin disease, called chloracne, which all was cured in a few months to a few years.
Also the ground of Seveso was affected in more or less serious ways. For this reason, the surroundings of the incident were categorised in three classes, the most polluted, the A-class had the highest dioxin content.

Cancer incidence in Seveso

Ten years after the incident, a large scale study by P. Bertazzi e.a. revealed some few more cases of some seldom occuring cancers (that was reported in the media) and some less cases of other, more common occuring cancers (that was not reported in the media!). The total result: in Seveso there are less cases of cancer, compared with a non-affected reference area.

Cancer incidence at Seveso, ten years after the accident: Average dioxin found in ground expressed in microgram I-TEQ per square meter. Average dioxin found in blood expressed in parts per trillion (ppt).

Cancer incidence at Seveso, ten years after the accident
zoneinhab.dioxin in
dioxin in
ref.181,579< 1n.d.  
Source: Cancer incidence in a population accidentally exposed to TCDD [12].

n.d.: not detectable

Recently, the WHO has declared the Seveso type dioxin (2,3,7,8 TCDD) as a human carcinogen, based on the consequences of severe accidents in several chemical works, where workers received extreme high levels of this dioxin type (tenthousends of times higher than background!). The rise of cancer incidences in a life time was app. 40% for the highest exposed people. That has to be compared with a 20 times (or 2,000%) rise in cancer incidence for smokers...
The other 209 types of chlorinated dioxins and furans are not classified until now, because of lack of reliable data.

Other diseases in Seveso

Some twenty years after the accident, the results of a long-term study were presented at a symposium [52]:

Data presented from health monitoring of the Seveso residents of 1976 to 1996:

Laboratory results showed minimal differences between exposed (even if very highly exposed) and controls in the period of acute exposure (1976-1977) for some liver function tests, complement haemolytic activity, white blood cells, lymphocytes, and haemoglobin. These differences were subclinical, faded and disappeared with time.

Part of the exposed people were controlled in 1992-1996. Results show that:

A control of people born after 1976 from exposed parents was recently started. In A zone from 9 months after the accident to December 1984, corresponding to about one TCDD half-life in adults, there was a significant modification of the sex ratio with an excess of females (26M vs 48F) associated to high TCDD exposure of both parents. This fact declined (60M vs 64F) there after and is no longer significant.

The latter is quite remarkable, because even after 8 years, half of the dioxins of the accident are still in human's fat. So if the amount is still 5,000 times higher (average for the highest exposed population in zone A) than for not-affected people, why is the ratio then back to normal if dioxins were the origin? Further that is contradicted by the fact that, with the same chemicals involved, the Vietnam war veterans show a higher than normal male to female birth ratio!
As we have learned from other discussions, the male to female ratio of births is highly influenced by sexual behaviour, which can be largely influenced by stress in war times or by health scares like in Seveso...

Toxicity of dioxins in small amounts

Even if there is a higher cancer incidence rate found at Seveso or other dioxin accidents, that wouldn't tell a lot about the possibility of having cancer at lower amounts. In animal experiments, hughe amounts of dioxin give more mortality, more cases of cancer and a lot of other unpleasant phenomens. According to Bruce N. Ames, the world famous toxicologist, dioxins are cancer promoting at low dose, when fed to animals after other carcinogens like aflatoxins, but give lower cancer rates when fed before other carcinogens. See Nature's Chemicals and Synthetic Chemicals: Comparative Toxicology [13].
In the same article, Bruce N. Ames compares the toxicological effect of the daily intake of dioxins with that of natural toxics in our food. If the effect of dioxins is related to the possibility of induction of the Ah-receptor in our cells, the daily amount of dioxins can be compared with the amount of natural indole carbinol found in 100 grams of cole slaw or 20 grams of Brussels sprouts, which has the same effect on the Ah-receptor. The possible carcinogenic effect of our daily intake is less than that of alcohol in drinking one beer in 125 years and the possibility of birth defects is less than drinking one beer in 3000 years.

Other subtile effects are found in the amount of the thyroxine hormone in newborn children, which is about 15% higher during several weeks, when the average dioxin content in mother's fat is twice the average. Dioxins are also suspected of playing a role in vitamin K deficiency in newborn, and of endometriosis.

Dioxins and mother's milk

In The Netherlands, together with Belgium the country with the highest dioxin content in mother's milk, an investigation was done to see if mother's milk still was good for children [50]. The amount of dioxin in mother's milk is about ten times higher than in cow milk, so newborn children can ingest relatively high doses of dioxin (and PCBs), compared to their body weight. Even before the child is born, dioxins and PCBs can pass from the mother to the child. In the investigation, children from mothers of two different regions (semi-rural and heavily industrialised) were compared, half of each region were fed with mother's milk, half with formula milk (or Artificial Baby Milk - ABM - the correct term used by the WHO). There was a wide variety in PCB/dioxin levels between individuals as well as in quantity as in toxicity of the different congeners, quantities ranging from 1:7 to 1:50.

The results of the investigation were:

"Prenatal PCB exposure has a small negative effect on the psychomotor score at 3 months of age. Breast-fed infants scored significantly higher on the psychomotor scale at 7 months of age [note: the breast-fed infants with the highest amount of dioxins/PCBs were equal to formula-fed infants]. The mental outcome at 7 months of age is positively influenced by breast-feeding per se, the perinatal exposure to PCB's and dioxins does not influence this outcome. Breast-fed infants never scored significantly lower compared to formula-fed infants. At 18 months of age the development is neither affected by PCB and dioxin exposure nor by feeding type."

As even in the highest contaminated group of the highest contaminated countries, the results of breastfeeding are in general better than for formula milk, then breastfeeding still is the best food for babies... Especially as the resistence of breastfeeded children to infections is much higher. The scaremongery of some groups and newspapers against the use of mother's milk, because of the high dioxin content is in any case not justified. Only the use of some extra vitamin K is justified.

Amounts and trends of dioxin found in mother's milk in different countries
All figures expressed in picogram I-TEQ per gram of milkfat.

Trends of dioxin levels in mother's milk
New Zealand5.8 
United Kingdom33.116.6
Source: WHO - 16th symposium on chlorinated
dioxins and related compounds [51]
Some countries only from the first round.

The little short- and longterm effects of dioxins, seen until now do not justify the enormous scare, abused by Greenpeace and other groups to accuse the chlorine industry of poisoning people and especially their children. Of course, that does not mean that one should not reduce the emissions of dioxins as far as reasonable possible. Lucky, the amount of dioxins in the food chain is lowering now, thanks to the measures taken at incinerators of all kind and at the metal industry. See also "Chlorine and bio-accumulation" (not yet ready) and Sources of dioxins.



A lot of the above investigations are biased by chlorine-free bio-accumulating materials like PAH's and nitro-PAH's. These were not measured in all of the above mentioned research. Because of several of those materials have dioxin-like effects, this would have given a clearer sight on the possible effects of dioxins alone.
If you see the enormous amounts of such materials, released from combustion, this would be worthwile an investigation. E.g. the combustion of one million tonnes of wood per year in The Netherlands gives, besides 24 times more I-TEQ dioxins than the whole chlorine industry and high amounts of carbon monoxyde, also 70 tonnes of PAH's. Besides the proven potent carcinogenic effect of several of its members, the direct toxicity is less pronounced. But even if we assume that the average toxicity is a thousand times less than of dioxins, the toxicity of PAH's only from burning wood is equivalent to 70 kilograms of I-TEQ dioxins per year! or 140 times the total emission of dioxins to air per year in The Netherlands.


There is no reason to treat the toxicity of dioxins different from chlorine-free toxic, persistent and bio-accumulating materials like PAH's. And there is no reason at all to accuse the chlorine industry to toxify mother's milk and poison unborn and newborn babies, like Greenpeace does.
Because of the enormous scare, introduced with the Seveso accident and the symbol function it has for Greenpeace and other environmental groups, high amounts of money are spent in research of the possible long-term effects of dioxin on the body. If you see the meager results of all those investigations, al that money was better spent in research of real problems, like the search for the mechanism which causes until now uncurable cancers and the search for possible remediants...


You are at level two of the Chlorophiles pages.

Created: March 9, 1996.
Last update: February 16, 1999.

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