Highest 8-Hour Average Concentration of Ozone
This threshold indicator has been retired and is no longer reported.
This indicator addresses the highest monitored ozone concentration averaged over every 8 hours for the calendar year. Ozone (O3), in high concentrations, can cause health effects such as lung inflammation and other respiratory illness. O3 can also cause damage to trees and plants at concentrations lower than the human health based ambient air quality standards. Standards, with varying time averaging periods, have been adopted to protect human health.
Ozone is a secondary pollutant created by reactions between sunlight and hydrocarbons (HC) and oxides of nitrogen (NOx). The primary sources of HC and NOx include in-basin mobile sources such as cars, trucks, boats, aircraft and off-road vehicles; biomass burning such as wood stoves, wildfires and prescribed burning; and consumer products such as solvents. Ozone is also transported into the basin to a lesser extent from populated areas surrounding the basin, and the ambient concentration of O3 is highly dependent on meteorological conditions such as sunlight, temperature, wind speed, and mixing conditions.
Status
Desert Research Institute
Evaluation Map
Current ozone monitoring locations in the Lake Tahoe Basin.
2015 Evaluation
- Status
- Somewhat Worse Than Target
- Trend
- Moderate Improvement
- Confidence
- High
Applicable Standard
8-hour Average
California: 0.070 ppm, not to exceed.
Nevada: no adopted standard
Key Points
- There is a statistically significant downward trend based on the long term trend line of sites that meet regulatory reporting requirements.
About the Threshold
- This indicator addresses the highest monitored ozone concentration averaged over every 8 hours for the calendar year. Ozone (O3), in high concentrations, can cause health effects such as lung inflammation and other respiratory illness. O3 can also cause damage to trees and plants at concentrations lower than the human health based ambient air quality standards. Standards, with varying time averaging periods, have been adopted to protect human health.
- Ozone is a secondary pollutant created by reactions between sunlight and hydrocarbons (HC) and oxides of nitrogen (NOx). The primary sources of HC and NOx include in-basin mobile sources such as cars, trucks, boats, aircraft and off-road vehicles; biomass burning such as wood stoves, wildfires and prescribed burning; and consumer products such as solvents. Ozone is also transported into the basin to a lesser extent from populated areas surrounding the basin, and the ambient concentration of O3 is highly dependent on meteorological conditions such as sunlight, temperature, wind speed, and mixing conditions.
Delivering and Measuring Success
Rationale Details
- For 2014, the latest year data is available, the maximum 8-hour ozone concentration at sites that met regulatory reporting requirements was located at Incline Village and was 0.071ppm, approximately 101 percent of the standard of 0.070ppm (Campbell 2015). Therefore, a status of somewhat worse than target was determined.
- There is a statistically significant downward trend based on the long term trend line of sites that meet regulatory reporting requirements. The trend line shows a 0.0004 ppm per year decrease from 1975 to 2014, a decrease of 0.57 percent per year in relation to the standard of 0.70 ppm (Campbell 2015). Therefore, a trend of moderate improvement was determined.
Confidence Details
- High. There is high confidence in the status determination because the data was collected using widely accepted protocols, was subject to quality assurance requirements, and has been collected continuously across the Region since 1975.
- High. The confidence in the long term trend is high, with confidence level in a trend of over 99 percent (P = 0.01)
- High.
Additional Figures and Resources
No photos available.
No documents available.