FIGURE 6-1 Scatterplot of estimated trends in pollutant emissions derived from emission inventories and changes in average pollutant concentrations derived from air quality monitoring networks. The squares indicate the trends for the period 1983–2002 (except for PM10 emissions, which are for the trend period 1985–2002) and the circles for 1993–2002. SOURCE: Data from EPA 2003.


The 1977 Amendments of the CAA state that

the Administrator shall promulgate regulations establishing an air quality monitoring system throughout the United States which (1) utilizes uniform air quality monitoring criteria and methodology and measures such air quality according to a uniform air quality index, (2) provides for air quaity monitoring stations in major urban areas and other appropriate areas throughout the United States to provide monitoring such as will supplement (but not duplicate) air quality monitoring carried out by the States required under any applicable implementation plan, (3) provides for daily analysis and reporting of air quality based upon such uniform air quality index, and (4) provides for record keeping with respect to such monitoring data and for periodic analysis and reporting to the general public by the Administrator with respect to air quality based upon such data.

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