Dioxins

Dioxins

What are dioxins?

also called "dirty dozens". ➔ a group of chlorinated organic chemicals with similar chemical structures. ➔ are insoluble in water but have avery high infinty for lipids. ➔ 2,3,7,8-Tetrachlorodibenzo-p-dioxin (2,3,7,8TCDD) is the most toxic dioxin. ➔

What are dioxins?

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Chlorinated chemicals with comparable structural and biochemical properties are called "dioxin-like compunds"and can act similarly in terms of dioxin-type toxicity.

How are dioxins formed? natural (through forest fires or volcanic activity) ➔ human activities ● municipal and domestic waste incineration ● burning fuels ● chlorine bleaching of pulp and paper ● chlorinated pesticides manufacturing. ● burning of materials containing chlorine ● cigarette smoke, exhaust from cars, etc. ➔

What happens when dioxins enter the environment? Dioxins in water bind strongly to small particles, organic matter or plankton. ➔ Dioxins deposited on land bind strongly to the soil ➔ Dioxins found in plants come from air and dust or from dioxin-containing pesticides or herbicides. ● Bioaccumulation ● Biomagnification ➔

What are the principal sources of exposures to dioxins? through the diet (essentially with fats from animal origin) ➔ food contamination ● contaminated animal feed ● sewage sludge contaminated with dioxins ● flooding of pastures ● waste effluents ● inappropriate food processing) ➔

What are the principal sources of exposures to dioxins?

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the daily intake of food containing dioxins in industrialized countries are in the oder of 1-3 pg I-TEQ. breast fed babies' daily intake of dioxins are hundred times greater than for adults.

What are the other possible sources of dioxin contamination?

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explosions of chemical factories workplace accidental contamination

How are dioxins mixtures accounted for? each dioxin is attributed a specific toxic factor (TEF). ➔ The TEF or Toxic Equivalency Factor refers only to adverse effects (e.g. cancer) following interactions with the cellular Ah-receptors ➔ this indicates a relative toxicity compared to the most toxic dioxin 2,3,7,8-TCDD, which is given a reference value of 1. ➔

How are dioxins mixtures accounted for? TEF values are attributed on the assumptions that a compound must: 1. show a structural relationship to the dioxins (PCDD's and PCDF's). 2. bind to the dioxin cellular Ah-receptors and cause effects vis this receptor. 3. be persistent and accumulate in the food chain. ➔

How do dioxins dioxin-like compounds act on living organisms?

can alter key biochemical and cellular functions by interacting with a cellular receptor called Ah, affecting the hormonal system and the way cells grow and develop. ➔ tends to bioaccumulate in fat and in the liver since it metabolize slowly. ➔

Do dioxins and dioxin-like compounds cause cancer? there is strong evidence that people accidentally exposed to the highest dioxin levels had an increased overall cancer risk (about 40% increase) ➔ a continuous exposure to between 2 and 7 pg TCDD per kg body weight per day increases the risk of cancer by 1%. ➔ also, a body burden of 2 600 pg per kg body weight increases the risks of cancer by 1%. ➔

What are other observed health effects? Mothers that were accidentally exposed to very contaminated rice oil, leading to an extremely high body burden of 2 to 3 million pg TEQ per kg body weight, gave birth to infants showing severe and persistent developmental and neurological effects. ➔ In workers exposed to high levels of dioxins in their workplace, health effects observed include changes in the blood composition and increased cardiovascular diseases and diabetes. ➔

What are other observed health effects? Some of the Seveso population, which was exposed to PCDDs and PCDFs at levels up to ten to hundred times higher than normal, suffered some temporary effects, such as a skin rash called chloracne and blood biochemistry changes. ➔ increase in male cardiovascular deaths and a decrease in the boy to girl birth ratio were observed. ➔

What are other observed health effects? Conjunctivitis ➔ sebaceous cysts and inflammation ➔ decreased nerve conduction velocity ➔ fatigue and malaise ➔ skin problems (hyperpigmentation and hyperkeratosis) ➔ increased death rate from non-cancer liver diseases. ➔

World Health Organization (WHO) activities related to dioxins

‘Code of Practice for the Prevention and Reduction of Dioxin and Dioxin-like PCB Contamination in Foods and Feed’. ➔ ‘Stockholm Convention’, an international agreement to reduce emissions of certain persistent organic pollutants (POPs), including dioxins. ➔ ‘Global Environment Monitoring System’s Food Contamination Monitoring and Assessment Programme ➔

How can one lesson his/her exposure to dioxins? Pay careful attention to fish advisories before eating fish from the Great Lakes or from inland lakes and streams ➔ Trimming fat from meat, consuming low-fat dairy products, and cooking foods in ways that decrease the fat content may also help reduce your level of dioxin exposure. ➔ Do not burn household trash in backyard barrels or wood-burning stoves. Dioxins can be formed in burning trash and could remain in your backyard soil for many years. ➔

How can one lesson his/her exposure to dioxins? Children should not play in soil or sediment near sites of known or suspected dioxin contamination. Children should wash their hands before eating to remove any dirt, and avoid putting toys or objects in their mouths. ➔ Clean fill dirt can be added over contaminated dirt in gardens and lawns if dioxin contamination is known or suspected. Care should be taken not to disturb the layer of clean soil covering the contaminated soil. ➔

Sources [1] [2] [3] [4] [5] [7] [8] [9]

www.greenfacts.org en.wikipedia.org www.michigan.gov www.niehs.nih.gov www.cqs.com www.cfpub.epa.gov www.who.int www.cfsan.fda.gov