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Sunday, October 26, 2014
Air Quality

What is Ambient Air Monitoring? 

… is measuring levels of pollutants in the air. Ambient air monitoring allows DAQ to measure trends in air quality.  In addition, monitoring allows the activation of emergency procedures to reduce air pollution events that may present a public health hazard. The results of these measurements are reported in near real time. (Please note that data has not been quality reviewed)

Monitoring air for pollutants is a complex technical task, requiring not only direct measurement, but also measurement standards and quality assurance to ensure that the information provides a correct understanding.

Where is the Air Monitored?  

The number of monitoring sites and their locations vary from year to year due to special purpose monitoring, temporary monitoring, and closing sites that are no longer needed.  Due to the unique shape and wind patterns in the Las Vegas Valley, high concentration levels occur in different areas for the different pollutants.  For example, CO occurs on calm cold days in the lowest (and eastern) part of the valley.  In addition, ozone occurs on hot sunny days in the northwest and at higher elevations.  Therefore, monitoring sites measure different pollutants based on their location within the valley.

What Role does EPA Play in the Monitoring in Clark County?

Clark County is a local government and U.S. EPA is federal government. EPA provides guidance and local governments perform the work. The locations of the monitoring stations are selected using EPA guidance and in general are established near population areas. The network of monitoring stations consists mostly of what EPA calls ‘State and Local Air Monitoring Stations (SLAMS)’.

Most stations are located in neighborhoods to assess exposure levels of the general population.  The network also characterizes pollution brought in (transported) into Clark County and background levels natural to Clark County.

What Pollutants are Monitored?  

The network contains sub networks for the EPA criteria pollutants PM10, PM2.5, CO, ozone (O3), and NO2 with threshold concentrations that are called National Ambient Air Quality Standards (NAAQS). Current monitoring efforts are primarily focused on ozone, the precursors of ozone and fine particulate matter (PM). Data from the network is used to demonstrate compliance with and/or progress toward meeting ambient air quality standards and to identify pollution trends.

Lead

Unlike the other criteria pollutants, the method to monitor Lead (Pb) is not continuous; therefore no “near-real” time measurements are available.  A filter based manual particulate sampler is used to collect the samples every 3 days.  Then the filters are sent, at the end of each calendar quarter, to the lab in North Carolina to determine the Pb concentrations.  The lab sends the results back to our office where it is entered into the EPA’s AQS database. 

Click here for the instructions to access the Pb data from the EPA’s AirData web page.

As data is obtained, it is stored electronically on a data-logger at each monitoring site.  The data is retrieved from each site over phone lines and is stored electronically on Servers. That data is then reviewed, edited, and after meeting all quality assurance requirements is electronically transmitted to the national EPA database for air monitoring data. 

Why No Monitors Along the Las Vegas ‘Strip’?

For about 20 years (1985-2005) pollutants were measured at as many as 4 different sites along the strip.  The results of this monitoring during the entire period have been low (at or below the detection level of the instruments).  Considering the terrain and the wind patterns in the Las Vegas Valley, the monitored results are unsurprising.  Therefore, this monitoring has been discontinued.

Monitoring Contact Information