To estimate health and economic effects associated with changes in air pollution, four factors must be determined: the dose response relationships, the susceptible populations, the relevant change in air pollution and an economic valuation of health endpoints (Bart Ostro, 1994). The first step is to develop estimates of the effects of air pollution on various health outcomes. Dose-response functions that relate health impacts to ambient levels of air pollution are taken from the published epidemiologic literature . This step involves calculating the partial derivative (or slope,b) of the dose-response function, to provide an estimate of the change in the prevalence of a given health effect associated with a change in outdoor air quality (A) . The next step involves multiplying this slope by the relevant population that is belived to be exposed and susceptible to the air pollutant effect under consideration (POP_i). For certain pollution related health effects, this may include the entire exposed population; for other effects there may be particularly sensitive subgroups such as children and asthmatics.

A third step in the calculation of health effects of air pollution involves the change in air quality (dA) under consideration. The actual change is dependent on both the policy issue under consideration and the available data. For example it may be relevant to consider the change from current air pollution levels to ambient air quality standard. A second change that might be relevant for consideration is a given percent reduction, such as 10 percent. A third method of determining the relevant change in air pollution is to assume that air quality changes in the some simple proportion to the change in emissions, as in a simple linear roll back model. In that case a 10 percent reduction in the tonnage of particulate emissions, for example, is assumed to reduce ambient particulate air pollution and health effects by 10 percent.

With this information, the estimated health impact can be represented as follows:

dH_i = b_i* POP_i *dA

where: dH_i = change in population risk of health effect i

b_i = slope from dose-response curve

POP_i = population at risk of health effect i

dA = change in air pollution under consideration