HUMAN CELL MUTAGEN FORMATION DURING THE THERMAL DESTRUCTION OF HAZARDOUS WASTES

Massachusetts Institute Of Technology, Cambridge MA

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Abstract

Description: The formation of mutagens during the pyrolysis and oxidation of wastes at Superfund sites will be determined in order to provide a basis for assessing the potential risks from high temperature destruction of wastes. The surrogate wastes to be studied have been selected because of their relevance to Superfund sites in general and to the Aberjona site in particular. The products of interest will be: a) PAHs; b) chlorinated mutagens; c) PCBs, which are known precursors to dioxins and dibenzofurans; d) arsenic and chromium submicron aerosols and residual particles. The specific aims of the project being proposed are: (1) To understand and control the chemistry responsible for mutagen formation, by identifying major molecular weight growth pathways which lead to the formation of biologically active species and their polycyclic precursors in combustion and pyrolysis systems, and to gain insight on the effect of chlorine on the chemical pathways of organic by-product formation. (2) To determine the biological activities, using human cell mutation assays, of combustion and pyrolysis products, in order to provide an indication on potential health hazards related to the application of thermal destruction technologies. (3) To test and refine chemical kinetic models which can be used to interpret the experimental results and to forecast product formation in different combustion conditions. (4) To identify parameters that are responsible for variations in the product spectrum, and that are amenable for use in the evaluation of operating windows and the selection of control strategies with the objectives of minimizing health risks, assessed by mutagenicity studies, posed by pyrolytic and oxidative thermal destruction processes. Research activities will define the pathways to soot growth and mutagen formation in oxidative and pyrolytic high-temperature environments, on the effect of chlorine on mutagen formation and distribution, on the influence of temperature on the mechanisms of growth and fragmentation of chemical species. The methods to be used in the proposed studies are: a) Pyrolysis studies will be conducted to determine the effect of temperature and time on product distribution covering the temperature range of 1000 to 250,000; b) A well-stirred/plug-flow reactor combination will establish the relevance of the pyrolysis reaction to combustors studies; c) The modeling activity will use molecular simulation techniques to generalize the results of the pyrolysis studies; d) The design of the bioassay experiments will be used to determine the nature of the mutagens produced under the different conditions; e) Reactor modeling will be used to translate the results to practical systems.