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This table summarizes high one-hour and eight-hour ozone averages in the metropolitan areas where the DAQEM monitors ozone.
Please Note: Data in this table is based on the number of monitors operating in an area, as well as on the severity of ozone. This data should not be used to perform comparisons between cities or across years without factoring in the number of monitors.
The peak one-hour and eight-hour averages are color-highlighted based on the EPA-defined Air Quality Index colors. (See Interpreting the AQI.)
| Metropolitan Area | One-Hour Averages > 124 ppb | Eight-Hour Averages > 75 ppb | ||||
|---|---|---|---|---|---|---|
| Peak Value | High Days | Peak Value | High Days | |||
| Date | ppb | Date | ppb | |||
| Greater Las Vegas | No averages over 124 | 07/07/2008 | 83 | 9 | ||
| Mesquite | No averages over 124 | No averages over 75 | ||||
| Jean | No averages over 124 | 05/11/2008 | 78 | 1 | ||
| Boulder City | No averages over 124 | No averages over 75 | ||||
| Apex | No averages over 124 | 05/30/2008 | 76 | 1 | ||
| Ozone averages are reported in parts per billion (ppb). | ||||||
| The High Days columns represent the number of days where one-hour or eight-hour ozone averages were above the thresholds of 124 ppb and 75 ppb respectively. | ||||||
What do the Numbers Mean?
The information in the table is composed of ozone measurements from monitoring sites across Clark County. There are two averaging periods that are of interest for ozone: a one-hour average and an eight-hour average. There are national air quality standards that have been established by the EPA for both of these averaging periods.
For the one-hour ozone average, a threshold of 124 ppb has been used to determine high value days. For the eight-hour ozone average, a threshold of 75 ppb has been used. Only averages that are higher than one of these thresholds appear in this table. The High Days column is a count of the number of days each metropolitan area experienced high ozone measurements (either one-hour or eight-hour) for the selected year. Out of all the averages above the thresholds, the peak or highest one-hour and eight-hour averages and the date they occurred are shown.
Ozone formation tends to be highest from March through October. Before May, there will be few if any metropolitan areas with high ozone readings. Some metropolitan areas never experience high ozone. In either of these cases, the table will show "No averages over 124", or "No averages over 75".
Interpreting the AQI
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Place your mouse pointer over the scale displayed above to view information about the Air Quality Index, and each of the rating levels.
The actual index calculation is different for each parameter measured and is specified by the EPA. The following table shows the various breakpoints used in calculating the AQI.
| AQI Breakpoint Definitions | ||||||
|---|---|---|---|---|---|---|
| AQI Range | 1hr Ozone in ppm |
8hr Ozone in ppm |
8hr Carbon Monoxide in ppm |
24hr Sulfur Dioxide in ppm |
24hr PM-10 in ug/m3 |
24hr PM-2.5 in ug/m3 |
| 0 - 50 | Not Defined | 0 - 0.059 | 0 - 4.4 | 0 - 0.034 | 0 - 54 | 0 - 15.4 |
| 51 - 100 | Not Defined | 0.06 - 0.075 | 4.5 - 9.4 | 0.035 - 0.144 | 55 - 154 | 15.5 - 40.4 |
| 101 - 150 | 0.125 - 0.164 | 0.076 - 0.095 | 9.5 - 12.4 | 0.145 - 0.224 | 155 - 254 | 40.5 - 65.4 |
| 151 - 200 | 0.165 - 0.204 | 0.096 - 0.115 | 12.5 - 15.4 | 0.225 - 0.304 | 255 - 354 | 65.5 - 150.4 |
| 201 - 300 | 0.205 - 0.404 | 0.116 - 0.374 | 15.5 - 30.4 | 0.305 - 0.604 | 355 - 424 | 150.5 - 250.4 |
| 301 - 400 | 0.405 - 0.504 | Not Defined | 30.5 - 40.4 | 0.605 - 0.804 | 425 - 504 | 250.5 - 350.4 |
| 401 - 500 | 0.505 - 0.604 | Not Defined | 40.5 - 50.4 | 0.805 - 1.004 | 505 - 604 | 350.5 - 500.4 |
| 500 | Not Defined | Not Defined | Not Defined | Not Defined | 605 - 4999 | 500.5 - 999.9 |