The evaluation of emissions from new energy sources has stimulated the development of new comparative approaches to health assessment studies. All energy sources that result in incomplete combustion are known to emit carcinogenic and mutagenic polynuclear aromatic compounds. Therefore, any toxicological assessment requires a comparative analysis of the new technology compared to the conventional technology. The authors have evaluated the mutagenicity and carcinogenicity of emissions from various conventional and alternative combustion sources and fuels in comparative studies utilizing a battery of short-term genetic bioassays in conjunction with animal cancer studies.