On the Trail of Atmospheric Mutagens and Carcinogens: A Combined Chemical/Microbiological Approach

Abstract

Major ecological problems of our polluted troposphere include airborne toxic chemicals, acid rain and photochemical smog, all three of which are now recognized as being closely related chemical phenomena. We also recognize that inorder to develop cost-effective strategies for their control, which protect public health and the environment, there must be close scientific interactions between chemists and biological scientists. For example, of rapidly emerging importance is the development of risk assessment evaluations for specific aspects of each of these problem areas. In preparing such assessments, chemists must define the “exposure,” and biological scientists the “effects.” In this paper, I discuss an example of how such close interactions proved indispensible in our search for atmospheric mutagens and carcinogens. Thus, an integrated chemical/ microbiological procedure for the isolation and identificationof particulate chemical mutagens in respirable diesel soot and ambient particles is described. Emphasis is placed on our use of the short-term, Ames Salmonella typhimurium bacterial mutagenicity test as a rapid, and relatively inexpensive, means of following the biological activities of these environmental mutagens through the chemical steps of their separation, isolation and identification from highly complex environmental samples. Possible mechanisms of formation of these particulate mutagens are discussed. They include the reactions of polycyclic aromatic hydrocarbons present on the surfaces of combustion-generated particles with gaseous co-pollutants such as nitrogen dioxide plus nitric acid, and ozone. In discussing this research on a societally “relevant” problem, we illustrate the importance of “Science as a Way of Knowing.” We further suggest that this integrated approach to scientific problem solving by chemical and biological scientists might serve as an example of a discussion topic on human ecology for undergraduate courses in the natural sciences.