The averaged concentrations from the monitoring sites in Mecklenburg county were then compared to the CEP modeled concentrations for each census tract in that county. For Lincoln county, the averaged concentrations for the one sampling site were compared to the CEP modeled air concentrations at the census tract level in the county. The tables below summarize the measured and monitored data. As seen in the tables, the measured data agree well with the monitored data. If the 1990 CEP data are accurate, it would appear that monitoring data obtained six to seven years later shows no significant change in pollutant levels for the BTEX compounds for Mecklenburg and Lincoln counties.
Automobiles also contribute to the pollutant emissions in the state.
Greater VMT generally indicates higher vehicle emissions, especially BTEX compounds. However, cars have also become more efficient during this time period. Thus, more efficient cars, in effect, balance the increased VMT and result in only a slight increase in pollutant emissions since 1990. The monitoring is conducted in winter and summer seasons and identifies specific hydrocarbons that are precursors of ozone. The results of the hydrocarbon monitoring were compared with CEP results for benzene and styrene, as shown in the table below.