Identificador: TDX:481
Autors: Fuster Camp, Gerard
Resum:
Polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) are ubitiquous organic pollutants. They are generated in small quantities as by-products of several chemical and combustion processes. The number and position of chlorine atoms at the benzene rings of PCDD/Fs molecules lead to 75 PCDDs individual compounds or congeners and 135 PCDFs congeners. Their high lypophilic character is the cause of their tedency to accumulate in soils, sediments, plants, animal and human adipose tissue. From several studies about impacts on humans to the congener 2,3,7,8-TCDD, the American Insitute of Medicine has described that there is evidence that exposure to this compound through the feeding chain and inhalation induces in humans several symptoms of toxicity: cloracne, systemic and neropsyquic. Respect to carcinogenic effects, the International Agency of Research on Cancer (IARC) reclassified in 1997 this congener from the group II of its classification: 'a probable carcinogenic agent in humans' to the group I: 'known carcinogenic agent in humans'. Concentration of a mixture of congeners is the result of adding up concentrations of each congener, and it is expressed in international toxic equivalents of the 2,3,7,8-TCDD (I-TEQ), which gives a toxic potential of the mixture. It is obtained from the toxic equivalent factors (TEF).During the last decade there has been an important development of methodologies which have searched to be an efficient tool within environmental management. Damage Function methods are the most usual. These use the variable concentration as the way to fix the impact by pollution. Nevertheless, the present study has looked to be an alternative, by adding the variable flow of pollutants as a tool for its calculations. Then, it has been developed and applied to the area Tarragona province an environmental management methodolgy based on the following four steps:a) Drawing up an inventory of PCDD/Fs sources to air, soil and water in Tarragona province. In order to know amounts of PCDD/Fs released to the environment by the identified sources, it has not been possible in many cases to have data coming from the own focus. In these cases, it has been resorted to an extrapolation: the use of emission factors and concentrations, which come from the literature and are representative of the industrial class in study. Global estimated emissions to air, land and water in 1999 were a mean of 175,7 g I-TEQ/year.b) The use of Substance Flow Analysis (SFA) has led to compartimentalize Tarragona province system into 30 environmental subsystems, with 88 input, ouptut and internal flows among them. It has been estimated the value of all non-measured flows, and reconciliated -i.e.: opitmization of uncertainty- of 32 measured flows. A complete reduction of industrial PCDD/Fs emissions implies a 1,7% reduction of the flow 'accumulation in human adipose tissue'.c) A risk assessment allows to estimate the impacts on population due to changes in environmental quality. The present study has focused on human health impacts, and inside them on carcinogenic risk, as a result of a reduction of PCDD/Fs emissions to air. The risk assessment has concluded that the reduction of the annual cancer risk rate for all the population, as a result of a total reduction of dioxin emissions to air in a specific industrial plant, has a meanvalue of 0,30 cases/year.d) As a final step, a Cost-Benefit Analysis (ACB) has concluded that in an american environment, the project of PCDD/Fs reduction in the plant is feasible only with a 15% probability, while in a european environment the project is in any way viable.
Repositori URV