What are dioxins?

Dioxins is the general name for two groups of 210 compounds with similar structures known as polychlorinated dibenzo-dioxins and polychlorinated dibenzofurans, of which 2,3,7,8-tetrachlorodibenzo-p -dioxin (TCDD) is the most toxic. Dioxins are non-flammable, colourless solids or crystals at room temperature with no perceptible odour. Dioxins are not produced intentionally as they have no commercial use.

How do dioxins get into the environment?

Dioxins may be present naturally during forest fires and may be produced as by-products of industrial processes. Small amounts may also be formed during domestic, municipal and industrial incineration processes or from metal smelting and refining. Dioxins are also found in small quantities in cigarette smoke and vehicle emissions. Dioxins may be present in contaminated soils and sediments where they may remain for a long time without being broken down. Industrial accidents have occurred in the past, such as in Seveso, Italy in 1976 in which high amounts of TCDD were accidentally released into the environment. However, due to strict regulations this is unlikely to occur again.

How will I be exposed to dioxins?

The main way in which people are exposed to dioxins is by eating food contaminated with them. Food such as meat, dairy products and fish may contain dioxins in very small amounts. Dioxins may be inhaled if they are present in the atmosphere but this is a minor way people may be exposed compared to food.

If there are dioxins in the environment will I have any adverse health effects?

The presence of dioxins in the environment does not always lead to exposure. Clearly, in order for it to cause any adverse health effects you must come into contact with it. You may be exposed by breathing, eating, or drinking the substance, or by skin contact. Following exposure to any chemical, the adverse health effects you may encounter depend on several factors, including the amount to which you are exposed (dose), the way you are exposed, the duration of exposure, the form of the chemical and if you were exposed to any other chemicals.

Dioxins vary in how poisonous they are from being highly toxic to virtually non-toxic. The most poisonous form of dioxin is TCDD. Many of the other dioxins are many times less toxic.

At the levels which occur in food and the environment, dioxins have no immediate effect on health if you are exposed for a short period of time. The potential risks to health come if you are exposed for a long period of time. Experiments in animals have shown that dioxins can affect the immune and reproductive system.  It is therefore important that the intake of dioxins is below that safety limits (tolerable daily intake) and that levels in the environment remain low.

Very high concentrations of dioxins (usually TCDD), compared to normal environmental levels, can cause an acne-like condition known as chloracne. This is a severe skin disease that mainly affects the face and upper body with acne-like spots, which may last several years after the exposure. Chloracne is difficult to cure and can be disfiguring. Exposure to high levels of dioxins may also cause rashes and redness, discolouration of the skin and an excess of body hair, as well as vomiting, diarrhoea, lung infections and damage to the nervous and immune systems. Liver damage has been observed in individuals exposed to high levels of dioxins.  However, these effects have only been seen in cases of deliberate poisoning and, in the past, in people working with chemicals contaminated with dioxins, or following industrial accidents.

Can dioxins cause cancer?

Dioxins can cause cancer in laboratory animals and there is evidence to suggest that exposure to dioxins at work in the past or following industrial accidents has been associated with an increase in the incidence of cancer in humans. The International Agency for Research on Cancer (IARC) has classified TCDD as a chemical which can cause cancer in humans. However, the IARC decided that it was not possible to classify the other forms of dioxins as to their ability to cause cancer in humans.

Do dioxins affect children or damage the unborn child?

Children are expected to be affected by dioxins in the same way as adults, although they may be more sensitive than adults.

Experiments on animals indicate that TCDD may reduce fertility and that exposure during pregnancy may produce adverse effects of the developing offspring. Provided that exposures to dioxins are below the recommended safety limits (tolerable daily intake) there would be no cause for concern.

What should I do if I am exposed to mixtures of dioxins?

It is very unlikely that the general population will be exposed to a level of dioxins high enough to cause adverse health effects.

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