Source resolution and risk apportionment of emission source categories for risk reduction purposes can be used to enhance the Bubble Policy of the Clean Air Act. This is performed by incorporating receptor modeling techniques of factor analysis and chemical mass balances to assess noncarcinogenic and carcinogenic inhalation risks to a target population for certain pollutants coming from major emission source categories in a steel plant air shed. Source resolution, using factor analysis, statistically interprets a “source” from ambient data. By subsequently quantifying risks from identified metal emission sources using chemical mass balances and risk apportionment, a total additive risk from main source contributors in the steel plant is estimated. From this methodology, the Bubble Policy can be enhanced by targeting only main risk sources or by “risk-trading” with minor impact sources to reduce the total risk (if deemed significant) without arbitrarily reducing risk for all sources in an industrial source complex’s “bubble.”