DrHannibal
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09.21.05 (2 years ago)
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Hey r u by any chance studying in Ukraine or have passed from there?  or else u must be following international news very keenly? But this question come little bit late, dont u think?
What Is Dioxin, Anyway?
Victor Yuschenko before and after dioxin poisoning
The photo shows the eventual winner of controversial Ukrainian elections held early this year.
On 5 September 2004, Viktor Yushchenko attended a dinner with leaders of the Ukrainian security services, with the aim to discuss their role in the forthcoming election campaign.
1 Three hours later, he developed a headache, and, the next day, an acute stomach ache started.
2 Food poisoning was the first diagnosis made by Ukrainian doctors.
Mr Yushchenko failed to recover in the next few days. His initial symptoms not only got worse, but he also started complaining of a backache, and the left side of his face became paralysed.3
On 10 September, five days after the gathering, Mr Yushchenko decided to seek treatment at the Rudolfinerhaus clinic in Vienna, Austria. Eleven doctors agreed on the diagnosis--"acute pancreatitis accompanied by interstitial oedematous changes."
Facial rash gives a clue
On his return to Ukraine, Mr Yushchenko claimed that "Ukraine's political cuisine" had tried to poison him.1 4 Ten days later, he started developing severe epidermal lesions on his face and on his torso.
By November, the rash had disfigured his face so dramatically that Mr Yushchenko looked considerably older than in photographs taken three months earlier. Experts around the world started speculating over the cause of the sudden facial transformation.
John Henry, a toxicologist at a London hospital, was one of the first to suggest that the changes were due to "chloracne," a hallmark of dioxin poisoning. It was not until 11 December, however, that the Austrian doctors treating Mr Yushchenko confirmed this theory.
On 17 December the Dutch laboratory where Mr Yushchenko's blood samples had been sent for analysis announced that the dioxin level was found to be 6000 times greater than normal. Mr Yushchenko's blood contained about 100'000 pg of dioxin per gram of blood fat, the second highest concentration ever recorded in humans. Also, the laboratory discovered that the blood was contaminated with a pure sample of TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin), the most harmful type of dioxin known so far, thus ruling out most inadvertent sources and implying that Mr Yushchenko had been poisoned deliberately.5 Not a single case of intentional dioxin poisoning had been reported before.
What are dioxins?
Dioxins belong to a group of very robust and mostly toxic chemical compounds known as persistent organic pollutants. Easily propagated over large distances by the means of air, water, and migratory species, these chemicals have a strong tendency to bioaccumulate.6 The term "dioxin" refers to a subgroup of persistent organic pollutants with similar chemical and biological properties.7
Dioxin-like substances are subdivided into three closely related families of chlorinated organic compounds--chlorinated dibenzo-p-dioxins, chlorinated dibenzofurans, and polychlorinated biphenyls. Whereas the latter used to be manufactured commercially for use in electrical equipment, dioxins belonging to the first two groups are created unintentionally.7 Although they can result from natural processes, such as volcanic eruptions and forest fires, they are predominantly produced as unwanted byproducts--for example, in any combustive activity in the presence of chlorine, chlorine bleaching of pulp and paper, as well as manufacturing and processing of certain types of chemicals, such as some pesticides and herbicides.8
More than 400 types of dioxins have so far been identified, but only 30 of these are considered to have significant toxicity, the most toxic and well studied being TCDD, also known simply as "dioxin."8 TCDD is the reference compound to which the toxicity of all other dioxin-like substances is compared. The toxicity of a mixture of dioxins is expressed in terms of its toxic equivalents, which is the amount of TCDD it would take to equal the combined toxic effect of all the dioxins found in that mixture.7
How are we exposed to dioxins?
Dioxins are found almost everywhere.8 Once they reach the environment, they are highly persistent.7 Due to their high lipophilicity, dioxins accumulate in the adipose tissue of animals and are slowly metabolised. In humans, TCDD has an estimated half life of seven years.9
The higher you climb up the food chain, the higher the dioxin concentration you can expect to find in a given species.8 For example, when dioxin settles on water, it will rapidly accumulate in fish, rather than in other animals or plants; the same principle applies for other ecosystems.
The US Environmental Protection Agency suggests that over 95% of the dioxin intake for an average human (background exposure) occurs through the ingestion of food, essentially of animal fats.7 People with vegan diets (who avoid the consumption of meat, fish, eggs, and dairy products) have significantly lower blood dioxin concentrations compared with the general population.10 Other means of exposure to dioxins include ingestion of other contaminated food, ingestion of contaminated water and soil, inhalation, and absorption through the skin.7
Background concentrations of dioxins in the general population are said to be declining, but they seem to be near concentrations that have been shown to have effects in the bodies of laboratory animals and humans. The US Environmental Protection Agency's philosophy is that no concentration is safe.11
What effects do dioxins have on our health?
Most insights into the effects of dioxins on humans have originated in the study of people with a greater than average exposure. This includes several industrial cohorts of chemical workers producing pesticides or herbicides and cohorts of civilian or military applicators of pesticides or herbicides (occupational exposure).12 Agent Orange, a herbicide used as a defoliant during the Vietnam War, for instance, contained minute quantities of TCDD as a contaminant. Many Vietnam veterans in the United States still have high blood concentration of dioxins.8 12
Another much researched cohort was exposed to TCDD in 1976 during a serious incident at a chemical factory in Seveso, Italy, when a cloud of toxic chemicals contaminated an area of 15 square kilometres with a population of 37'000 people.8 Dioxins have numerous toxic effects on our body (table). The International Agency for Research on Cancer classified TCDD as a "known human carcinogen" in 1997.8
One of the trademarks of dioxin poisoning is undoubtedly chloracne--or maybe it is Yushchenko disease? Two similar names were given to the manifestation of chloracne in two well defined cohorts with dioxin poisoning in Japan and Taiwan in the 1960s and '70s--Yusho disease and Yu-Cheng disease.13
Chloracne is an acneiform eruption due to systemic poisoning by chemical chloracnegens, such as dioxins. The most commonly affected areas of the human skin are below and to the outer side of the eye and behind the ear, although the cheeks, forehead, and neck are quite often blighted as well. The basic lesions, involving almost every hair follicle, are small infundibular cysts containing keratotic material. Hyperpigmentation often accompanies the lesions.14 Chloracne usually disappears on its own once the blood concentration of dioxin is reduced.13 Some effects of dioxin poisoning on our health 8, 13, 15
Skin Chloracne; hyperpigmentation
Gastrointestinal system Abdominal pain; nausea and vomiting; anorexia; weight loss; altered liver function or fatty liver
Blood and cardiovascular system Hyperlipidaemia; atherosclerosis
Endocrine system Type II diabetes; suppression of thyroid function
Nervous system Numbness of extremities
Immune system Immune system depression or increased susceptibility to infections; thymic atrophy
Reproductive system Endometriosis; decreased fertility; inability to maintain pregnancy; decreased testes size; reduced sperm counts; lowered testosterone
Development (children) Developmental delays; learning disabilities; behavioural problems; abnormal development of teeth
Teratogenicity Various birth defects
Carcinogenicity Various cancers
General Muscle wasting; chronic fatigue
How do dioxins work on a molecular basis?
One of the limiting factors for dioxins to be able to act upon our body is their binding to the Ah (aryl hydrocarbon) receptor. This is located in the cytosol and forms a complex with four other proteins. Upon dioxin binding or binding of endogenous ligands, the complex dissociates, and the Ah receptor becomes free. The Ah receptor influences gene transcription directly as a transcription factor or indirectly by interacting with various cell signalling pathways. It is thought that the Ah receptor plays an endogenous role in development and homoeostasis.15 16
Last December, an unnamed British expert played down Yushchenko's poison theory, saying that the marks on his face were "much more likely to have been caused by stress."1 Interestingly, as Fumio Matsumara of the University of California explains, there may be a direct relationship between dioxin poisoning and stress. In a scientific review, he said that the toxic actions of dioxins are the result of a major cellular stress response triggered by the activation of the Ah receptor. He compares the effects of dioxin poisoning with the reactions to well established cellular stressors such as lipopolysaccharides and points out numerous striking similarities on molecular, biochemical, and symptomatic levels.15 Research is needed to understand the pathophysiology of the health effects of dioxin.
Is it possible to treat dioxin poisoning?
There is no regimen for TCDD detoxification. Increased faecal excretion, which already accounts for up to 50% of overall elimination of TCDD, may accelerate detoxification.17 This may be achieved with olestra, a dietary fat substitute that is neither digested nor absorbed by the human gastrointestinal tract.18 Other medicines, such as colestimide, a cholesterol lowering drug, have also been shown to decrease the blood dioxin level in humans.19 Further treatment options include symptomatic treatment, for example with isotretinoin, which may help to relieve symptoms of chloracne.20
Women can also excrete dioxins across the placenta and through lactation. This results in shorter half lives of dioxins in women, however, it also exposes their unborn or newborn children to relatively high concentrations of dioxin, risking teratogenicity and developmental defects. Breastfeeding, however, is highly recommended, as its benefits outweigh the risks of dioxin exposure by far.
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