Fine Particulate (PM 2.5) Monitor Readings

 

The NC Division of Air Quality (DAQ) is required to evaluate fine particle pollution (known as PM 2.5) to determine if Catawba County is in attainment for the federal standards for PM 2.5. Specifically, NCDAQ evaluated the following data yearly as part of the air quality analyses:

 

  • Annual PM 2.5 Averages – Average daily reading during the course of one calendar year. PM 2.5 monitor readings usually are taken and analyzed every third day during the course of a year.

 

  • PM 2.5 3-year Averages – Average of the last three years, used to determine change over longer periods of time.

 

  • PM 2.5 98th Percentile Daily Reading – 3rd or 4th highest reading during the course of a year. PM 2.5 monitor readings usually are taken and analyzed every third day during the course of a year.

 

Due to the population size of the Hickory-Lenoir-Morganton Metropolitan Statistical Area (MSA), the region is required by the US Environmental Protection Agency (USEPA) to have one PM 2.5 monitor. The monitor is located one block west of US 321 close to the water tank owned by the City of Hickory.  Additional monitoring related to the official monitor is also taking place on the site. 

 

The PM 2.5 federal standard is a three-year average of annual PM 2.5 monitor readings. A violation occurs if a PM 2.5 monitor exceeds the standard. The Federal standard for PM 2.5 until 2012 was 15 micrograms per cubic meter. The standard was lowered in December 2012 to 12 micrograms per cubic meter.

 

Annual PM 2.5 Averages

 

Table 1 shows the yearly readings for the Hickory monitor between 2004 and 2014. The design values are presented in micrograms per cubic meter, with values exceeding the standard highlighted with grey shading and bold lettering. 

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In 2005 and 2006 the Hickory PM 2.5 monitor recorded violations of the standard. Data in Table 1, however, shows significant decreases in PM 2.5 design values since 2006 in the region, which can be attributed to multiple factors, including traffic improvements, mobile source emission reductions, alternative fuels and technologies, the addition of pollution control scrubbers at the Marshall Steam Station (coal fired electric power plant owned by Duke Energy that located in southeastern Catawba County), more favorable weather patterns and poor economic conditions. As a result of these factors, annual PM 2.5 readings at the Hickory Water Tower Monitor have been less than 10 micrograms per cubic meter since 2012.  

 

 

Table 1.

Annual PM 2.5 Averages (micrograms per cubic meter), 2004-2017

 

 

 

 

 

Note: The annual average in 2005 & 2006, exceeded the annual federal standard of
15 micrograms/per cubic meter. Source: USEPA and NC Division of Air Quality, 2018.

 

 

PM 2.5 3-year Averages

 

The PM 2.5 three-year average is a health based standard that is used to see how air quality conditions are changing over time.  It is calculated by averaging the annual value for three years.  Since the design value is an average of three years, a decrease may be the result of one really good air quality year; or conversely, an increase may be the result of one bad air quality year. Therefore, looking at the trends of the 3-year average can give insight as to how the air quality in an area is improving. 

 

In December 2004 USEPA placed all of Catawba County in “non-attainment status” for PM 2.5 based on the three-year average between 2001 and 2003 being slightly above the 15.0 standard. Table 2 displays the 3-year averages for the Hickory PM 2.5 monitor between 2004 and 2014. Results show that the monitor was in nonattainment for the 15 micrograms per cubic meter PM 2.5 standard through 2005-2007. Over the past decade PM 2.5 levels at the Hickory monitor have fallen substantially. As a result of improving PM 2.5 levels, in December 2011 Catawba County was moved out of nonattainment status by USEPA and was placed instead in “maintenance (attainment) status.” The 2011-2013 and 2012-2014 three-year averages for the Hickory PM 2.5 monitor were less than 10 micrograms per cubic meter.   

 

 

Table 2.

PM 2.5 3-year Averages (micrograms per cubic meter), 2004-2017

 

 

 

 

 

 

 

Note: The annual average in 2004 - 2006 and 2005 - 2007, exceeded the annual federal standard
of 15 micrograms/per cubic meter. Source: USEPA and NC Division of Air Quality, 2018.

 

 

PM 2.5 98th Percentile Daily Reading

 

Besides setting an annual standard, USEPA also has a daily PM 2.5 standard to protect public health. The annual federal standard, established in 2006, is 35 micrograms per cubic meter. The standard is calculated at the 98th percentile for each year (USEPA uses a three-year average for the standard), which is equivalent to 3rd or 4th highest daily reading during the course of a year (PM 2.5 monitor readings usually a taken and analyzed every third day during the course of a year). The PM 2.5 98th percentile daily reading has been below the standard every year except in 2005 (Table 3). The three-year average has never violated the daily standard.

 

Table 3.

PM 2.5 98th Percentile Daily Reading (micrograms per cubic meter), 2004-2017

Yearly Readings

3-Year Average

Note: In 2005, the annual average exceeded the annual federal standard
of 15 micrograms/per cubic meter. Source: USEPA and NC Division of Air Quality, 2018.

 

 

Ozone Monitor Readings

 

The NC Division of Air Quality (DAQ) is required to evaluate design value (DV) trends and ozone exceedance trends to determine if any of the State’s monitors show increases in ozone formation.  Specifically, the NCDAQ evaluates the following data as part of the air quality analyses:

 

  • 8-hour Ozone Design Value Trends – Most recent design values (1 and 3 year average of the 4th highest 8-hour ozone average), compared to the trend in design values from the 2005 timeframe to present.

 

  • 8-Hour Ozone Exceedances – Number of exceedances of the 8-hour ozone standard at each monitor in the EAC areas for the most recent ozone season, compared to the number of exceedances at each monitor from 2005 to present.

 

Due to the population size of the Hickory-Lenoir-Morganton Metropolitan Statistical Area (MSA), the region is required by the US Environmental Protection Agency (USEPA) to have two ozone monitors.  The monitors are located in Alexander County (Taylorsville) and Caldwell County (Lenoir).

 

The ozone federal standard is a three-year average of the fourth highest daily 8-hour ozone monitor reading.  A violation occurs if an ozone monitor exceeds the standard.  The Federal standard for ozone until 2008 was 85 parts per billion (ppb).  The standard was lowered in 2009 to 75 ppb.  In October 2015 the ozone standard was lowered again to 70 ppb.

 

8-hour Ozone Design Value Yearly Trends

 

Table 1 below shows the trend in 8-hour ozone values at monitors in Alexander and Caldwell County. The design values are presented in ppm, with design values exceeding the standard highlighted in gray with bold lettering.

 

 

Table 1. 4th Highest 8-Hour Ozone Values (parts per billion), 2005-2018

*2015 data is preliminary and not been varied by USEPA. Source: USEPA and NC Division of Air Quality, 2018.

 

Data in Table 1 shows significant decreases in ozone design values over the past decade in the region, which could be attributed to multiple factors, including traffic improvements, mobile source emission reductions, alternative fuels and technologies, more favorable weather patterns, and poor economic conditions. 

 

8-Hour Ozone Exceedances

 

No daily 8-hour ozone exceedances have occurred over the past decade at either the Alexander County or Caldwell County monitor.

  

4th Highest Value Trends

 

The design value is calculated by averaging the 4th highest 8-hour ozone value for each of three years.  Since the design value is an average of three years, a decrease may be the result of one really good air quality year; or conversely, an increase may be the result of one bad air quality year.  Therefore, looking at the trends of the 4th highest value can give insight as to how the air quality in an area is improving. 

 

Table 2 displays the 4th highest daily 8-hour ozone 3-year averages for the region.  Three year averages at both monitor locations have been decreasing since 2005.  The 2013-15 4th highest daily 8-hour ozone monitor averages are currently well below the current federal standard of 70 parts per billion.

  

 

Table 2.Fourth Highest 8-Hour Ozone 3-year Averages (or Design Values) (parts per billion), 2005-2018

*2018 data is preliminary and not been varied by USEPA.  Source: USEPA and NC Division of Air Quality, 2018

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