One of the more important health risk factors in the developing and developed world alike, especially for middle-income industrializing countries, is the concentration of particulate matter of diameter 2.5 micrometers or less per cubic centimeter in urban air (ENVPM2PT5). [1]   It is a major cause of respiratory infections, respiratory diseases, and cardiovascular disease in adults 30 and older.  In IFs it affects mortality rates via the mechanism that the model uses to modify cause-specific mortality from the distal driver formulation by using information concerning actual risk level in a country.  The core of that approach is to compare the risk-specific population attributable fraction (PAF) of total morality as calculated from the distal drivers with the PAF calculated from the actual level of the risk in the country.  

The figure below shows the approach for outdoor urban air pollution, focusing on the measure of ENVPM2PT5.  The two key variables in the distal driver formulation at any point in time (ignoring the technology factor that adds dynamics over time) are GDP per capita at purchasing power parity and years of adult education.  They are used in a cross-sectionally estimated function to calculate outdoor air pollution that then produces the associated implicit PAF.  IFs uses an alternative and more risk-factor specific formulation to forecast values of outdoor urban air pollution use over time.  The PAF associated with this explicit representation of ENVPM2PT5 is compared with the PAF from the implicit calculation and the comparison alters the actual mortality pattern. 

To calculate ENVPM2PT5 the explicit formulation also uses GDP per capita, as in the distal formulation, but augments the spending of a country on health as a portion of GDP (which appears to serve reasonably well as a proxy for more general attention to the environment).  For the actual equation, see the topic on outdoor urban air pollution equations in the health documentation .  A multiplicative parameter ( envpm2pt5m ) can be used to change urban air pollution in scenario analysis.  Another parameter ( envpm2hldsw ) can be used to hold the level of urban air pollution at the level of the first year, an approach useful for counterfactual scenario analysis.