With the term dioxins commonly indicates a group of substances (polychlorinated dibenzodioxins, polychlorinated dibenzofurans, and some polychlorinated biphenyls also known by their respective abbreviations: PCDD, PCDF and DL-PCB) which have very similar chemical, physical and toxicological characteristics.
Dioxins are not voluntarily produced substances. In fact, they mostly derive from natural combustion processes (such as forest fires or gas emissions from volcanoes) or from specific human activities such as waste incineration or industrial production processes. Currently, changes in the production methods of industrial plants and, above all, in waste incineration techniques, have greatly reduced the release of dioxins into the environment.
Polychlorinated biphenyls (PCBs), industrial products that have now been banned worldwide for years, have been widely used in the past in a number of applications. Currently, their presence in the environment is mainly due to the release of old products or appliances that have not been properly eliminated or from “environmental compartments” (such as sediments) where they have accumulated over the years.
This could happen because the dioxins, belonging to the class of persistent organic pollutants (known as POPs from the English persistent organic pollutants), have a high chemical stability (that is to say that they hardly degrade), they are not easily dissolved in water. and, having characteristics similar to fatty substances, they are able to remain for quite a long time both in the environment and inside organisms, including the human body, where they are mainly located in the fatty tissue (adipose): to eliminate 50% of a dioxin dose it takes more than 10 years. Furthermore, these chemicals are able to spread easily in the environment, even reaching very far distances from the place of release. They are therefore present everywhere on Earth, even in extreme and isolated areas of our planet, such as the poles.
As a consequence of these characteristics, their current presence in the environment derives, rather than from new emissions, from their accumulation which took place slowly over the years. From the environment, where they are linked to the organic part of the soil and sediments ( deposits of solid material) marine and lacustrine, dioxins enter the food chains, accumulating in the smallest organisms, then in the fats of the larger animals that feed on them up to humans who are exposed through food (biomagnification).
Sources of exposure and levels in humans
The main source of human exposure to dioxins (approximately 90%) is represented by food. Foods with a higher fat component (such as meats, some fish species, cheeses and other dairy products) are those with the highest levels of dioxins.
Other possible routes of exposure, although generally much more limited, are constituted by "inhalation and" ingestion of dust or earth, or by contact with the skin.
Since these pollutants are present everywhere, both in the environment and in food, the population has been, and continues to be, constantly exposed (albeit at lower and lower levels over the years).
Consequently, dioxins are present in measurable quantities in the organism of each individual internal dose detected in a person and determined not only by the current exposure but also by that which occurred over the years, given the long residence times of these pollutants in the organism. Currently, the internal dose of dioxins of the general population, determined through biomonitoring studies, is on average very low and continuously decreasing (already from the 70s to the end of the 90s it had dropped by about 4 times). The presence of dioxins in the blood, or in the body tissues, of an individual is indicative of a certain and occurred exposure; however, this does not necessarily mean the presence of related diseases.
Effects on health
Limited exposure over time but to high levels of dioxins (acute) can also cause serious effects on human health such as:
- skin diseases (such as chloracne, which manifests as juvenile acne-like rashes and pustules throughout the body that can persist for years, leaving permanent scars)
- changes in liver functions
- difficulty in glucose metabolism
This type of exposure, although rare, occurred in the past both as a result of industrial accidents (such as that of 1976 at the chemical plant in Seveso, in Italy, where a cloud rich in one of the most common substances was released and spread. toxic: dioxin TCDD) and for cases of involuntary or voluntary poisoning (such as that of Ukrainian President Viktor Yushchenko in 2004).
Exposure to lower doses of dioxins, but for longer periods of time (chronic), can:
- cause damage to both the immune and endocrine systems
- interfere with the physiological balance of thyroid and steroid hormones (action by endocrine disruptors)
- determine effects on the development of the fetus, when exposure occurs during pregnancy (prenatal exposure) or in the stages immediately following birth (postnatal exposure)
Some of the polychlorinated dibenzodioxins and polychlorinated dibenzofurans and all polychlorinated biphenyls are considered carcinogenic to humans. They can in fact cause tumors of the lymphatic tissue, tumors of the hematopoietic tissue (thus affecting organs and tissues responsible for the production of red, white blood cells and platelets) different forms of leukemia, non-Hodgkin's lymphomas and breast cancer. For this reason the International Agency for Research on Cancer (IARC) classifies some dioxins in the group 1 among the carcinogenic elements for man.
Prevention, control and useful advice
For several decades, effective prevention, control and reduction measures for human exposure to dioxins have been implemented by the competent authorities. In the countries of the European Union, for example, the emissions produced by new industrial plants have been reduced by 80% and are still decreasing.
Following the 1976 Italian accident in Seveso, the European Community in 1982 approved the so-called "Seveso Directive", now in its third revision, which included, among other things, the registration of industrial plants at risk, the identification of substances dangerous treated and the preparation of specific prevention and emergency plans.
Given that foodborne transmission is responsible for more than 90% of general exposure, in Europe the concentration limits of dioxins present in food, identified in such a way as not to cause effects on the health of the consumer, are regulated by law and periodically monitored. through specific official surveillance programs.
At the individual level, the prevention and control measures that can be implemented are rather limited and mostly consist of:
- reduce the consumption of animal fats and other foods of animal origin (meat, dairy products, eggs)
- follow a diet that is as balanced and varied as possible: a diet consisting mainly of a single type of food from very polluted areas (such as fish from the Baltic) will lead to a "greater exposure than a diet rich in foods of plant origin and in general very varied
- evaluate, reading the label carefully, where the food we are about to buy comes from, favoring those that are produced in areas where controls are in place
- avoid burning waste potentially containing plastics
Agency for Environmental Protection and Technical Services (APAT). Dioxins Furans and PCBs
Communication from the European Commission to the Council, the European Parliament and the European Economic and Social Committee concerning the implementation of the community strategy on dioxins, furans and polychlorinated biphenyls (COM593)
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Expert Meeting on the Effectiveness Evaluation of Implementation of the Stockholm Convention for PCB and Sixth Meeting of the Advisory Committee of the PCB Elimination Network (PEN)
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