For example, an oil drilling facility may emit far greater mass of pollutants than a refueling station. However, if the oil drilling is located on a platform 10 miles offshore and the refueling station is in an urban area, then very few people will be exposed to the emitted pollutants. A relatively small reduction in emissions from the refueling station may yield a larger reduction in health impact than a large reduction at the oil platform. Policy makers may also be interested in comparing the intake fraction among various groups within the population to assess environmental justice. For example, it may be of interest to determine the intake fraction of low-income residents of a town versus high-income residents of the town.