What’s measured This section identifies the percentage of Air Quality Index (AQI) days per year in the Unhealthy ranges for the Charlotte-Gastonia-Rock Hill Metropolitan Statistical Area (MSA). The EPA calculates a daily AQI based on the measurement of five major air pollutants regulated by the Clean Air Act, as recorded at approximately 4,000 monitoring stations across the country. The five pollutants are: ground-level ozone, particle pollution (also known as particulate matter), carbon monoxide, sulfur dioxide and nitrogen oxides (NOx). A daily index value is calculated for each air pollutant measured. The highest of those index values is the AQI value, and the pollutant responsible for the highest index value is the Main Pollutant. AQI data are summarized annually for counties and Metropolitan Statistical Areas (MSAs), categorized by number of days Good, Moderate, Unhealthy for Sensitive Groups and Unhealthy, Very Unhealthy and Hazardous. This indicator looks at the number of days reported in each year with an AQI of Unhealthy for Sensitive Groups, or worse, and divides by the number of days in the year with a reported AQI. Generally, the number of AQI days each year corresponds to the number of days in the year. Please note that not all monitoring stations record all five pollutants, and not all counties in the Charlotte region have monitoring stations. For this reason, the 7-county Charlotte-Gastonia-Rock Hill MSA data has been used rather than county-level data for this indicator. The MSA includes Cabarrus, Gaston, Lincoln, Mecklenburg, Rowan, Union and York counties. Why it’s measured AQI values indicate health concerns associated with air pollution. AQI values range from 0 to 500, with values of 100 corresponding roughly to the national air quality standard for the pollutant. AQI values above 100 are considered unhealthy (code orange,red,purple or maroon). Those between 50 and 100 indicate acceptable air quality for all but exceptionally sensitive individuals (code yellow) and those below 50 represent air quality with little to no associated health risks (code green). Indicator results In 2006, the percentage of AQI days per year in the Unhealthy ranges for the Charlotte-Gastonia-Rock Hill MSA was 5.5. Twenty out of 365 AQI days in 2006 were Unhealthy for Sensitive Groups or worse. This is lower than the 10-year average of 7.6 percent. The highest result was reached in 1998, when 14.0 percent of AQI days were in the unhealthy ranges. The lowest result occurred in 2004, when only 1.6 percent of AQI days were in the unhealthy ranges. In 2006, particulate matter was the main pollutant on 223 AQI days, with ground-level ozone accounting for the remaining 142 AQI days. For the prior seven years, particle pollution was also the main pollutant on the majority of AQI days. Evaluation The trend shows the MSA’s percentage of unhealthy AQI days has declined over the past decade. However, a large portion of the region was declared in Non-Attainment of the Clean Air Act by the EPA in 2005. A contributor to the MSA being in Non-Attainment, despite a decline in unhealthy air days, is that the EPA raised the standard for attainment to better protect public health. Although the region’s air quality has improved, further improvement is still needed. The region is required to implement a plan for returning to compliance with the Clean Air Act. Factors influencing AQI unhealthy air days in the region include mobile and stationary emissions, wind patterns and summer air temperatures. Two of those factors are not under anyone’s control. Being in the South, the region typically experiences higher summer air temperatures than the national average, thus contributing to ground-level ozone formation. The region also is prone to stagnating air conditions, a phenomenon in which air masses settle in one location and do not disperse pollutants effectively. The burden for continuing to improve on the AQI trend rests with controlling and reducing mobile and stationary emissions. Connections Poor air-quality days can be correlated to respiratory health, especially of vulnerable populations such as children, the elderly and individuals with lung disease, asthma or other respiratory conditions. Recommended restriction of outside activity during Unhealthy AQI days reduces quality of life. Corporate and individual decisions to remain in or relocate to the region may be affected by these health and quality-of-life considerations. |