Występowanie dioksyn i furanów w środowisku

Polychlorinated p-dibenzodioxines and polychhrinated dibenzofuranes (PCDD/F) belong to a widespread group of longlived chlorinated polycyclic aromatic compounds which are hazardous to the environment because of their toxic, mutagenic and carcinogenic character. Under natural conditions, PCDD/F originate during volcano eruption, forest fire and non-industrial low-temperature combustion. But these proces-ses contribute only slightly to the presence of PCDD/F in the natural environment. The main source of their origin is in the side reactions concomitant with the manufacture of chlorinated organic compounds. The largest portions of PCDD/F come from coal and liquid fuel combustion, from solid waste disposal and high-temperature industrial processes (metallurgy, cement manufacture, incineration of chemical wastes). PCDD/F enter the environment together with flue gases or solid wastes. In the 1940s, PCDD/F concentrations were low, but they increased rapidly in the next decades to reach a maximum in the 1980s. PCDD/F content in vegetation measured in 1980 was 7 to 8 times as high as in 1900. In rough estimates, the overall CDD/F deposition on land and oceans today amounts to 12,500 kg/a and 610 kg/a, respectively. Their lipophilic properties make PCDD/F accumulate in the adispose tissue. In the 1980, PCDD/F concentration in humans averaged 53.2 mgI-TEQ/kg. The largest PCDD/F portions (99.3%) are taken in by digestion (milk, 65.8%; meat, 26.1%; leaf-vegetables, 7.4%). The half life of PCDD/F in human organisms varies from 7 to 11 years. It has been anticipated that a harmless PCDD/F dose to humans ranges between 0.01 and 0.1 mgI-TEQ/kg day, the daily intake averaging 150pgI-TEQ/body.The carcinogenic index was found to be 1.5x10[5] ngI-TEQ/kg day. Modem solid waste incinerators meet the allowable PCDD/F concentration in the flue gas, which is below 0.1 ngI-TEQ/m3. Under such conditions, the carcinogenosis risk approaches 5x10[-8] incidents in a population with very high exposure to PCDD/F.