Some knowledge of the potential genetic activity of a complex environmental mixture may be gained from an assessment of the genetic activity of its component chemicals. The expanded Genetic Activity Profile (GAP) data base provides a computer-generated graphic representation of genetic bioassay data as a function of dose of the substance tested. In addition, the Atmospheric Chemical Compound (ACC) data base contains information on chemical structures, properties, detection methods and sources of chemicals found in ambient air. Using the combined data bases, information on the quantity of an individual chemical present within a mixture or fraction of a mixture may be related to the quantity (lowest effective dose, LED) of the chemical required to demonstrate a positive response in one or more genetic bioassays. Quantitative information on the carcinogenic potency of each individual compound (TD50 value) may also be related to the quantity present in the mixture or mixture fraction. In turn, the quantity of the chemical in the complex mixture to which humans are exposed may be estimated and used to calculate the percent human exposure dose/rodent potency dose (HERP) for the chemical.