Indicator
Highest 24-Hour PM2.5 Concentration
2019 Evaluation
View in Threshold Dashboard

PM2.5 is very fine particulate matter, 2.5 micrometers and smaller. This indicator measures the 3-year running average of the 98th percentile 24-hour average concentration of PM2.5. The highest PM2.5 concentrations in Tahoe are associated with wildfires. Particulate matter less than or equal to 2.5 microns in size (PM2.5) is associated with a variety of human health concerns, including asthma, lung diseases, and heart disease. The primary sources of PM2.5 in the Tahoe Basin are residential fuel combustion, campfires, wildfires, prescribed fires, motor vehicles, and dust from unpaved roads. PM2.5 is monitored by TRPA and partners at three sites around the Basin.

24-Hour Pm2.5 Concentration.jpg
Status

PM2.5 monitored in the Tahoe Basin from 1990 to present.

Desert Research Institute

2019 Evaluation
See how thresholds are evaluated
Status
Considerably Better Than Target
Trend
Moderate Decline
Confidence
High
Applicable Standard
AQ11: Maintain Particulate Matter2.5 at or below 35µg/m3 measured over a 24-hour period using gravimetric or beta attenuation methods or any equivalent procedure which can be shown to provide equivalent results at or near the level of air quality standard.
Key Points
  • The Tahoe region continues to enjoy high air quality. The highest reading at any site was 60% of the threshold standard value.
  • The increasing extent and severity of wildfires is likely contributing to the increasing trend in peak PM2.5 concentrations. The highest 24-hr concentration of PM2.5 is heavily influenced by wildfires. In years where wildfire smoke is blown into the region, the highest 24-hour concentrations of PM2.5 spike.
Evaluation Map
Description

The location of air quality monitoring stations in the Lake Tahoe Basin. PM2.5 is monitored by TRPA and partners at three sites around the Basin.

About the Threshold
This indicator measures the 3-year running average of the 98th percentile 24-hour average concentration of PM2.5. Particulate matter less than or equal to 2.5 microns in size (PM2.5) is extremely small and can be inhaled deep into the lungs causing or aggravating asthma, lung diseases, and heart disease. Some particles pass into the bloodstream and some are considered carcinogens.
Particulate matter pollution consists of very small liquid and solid particles in the air. The primary sources of PM2.5 in the Lake Tahoe Region are residential fuel combustion, wood smoke from wildfires and prescribed fires, motor vehicles, and paved and unpaved road dust. PM2.5 results from primary emission sources, condensation of semi-volatile organic gases, and from secondary formation from reactions of gases in the atmosphere. Small particles are also transported into the Lake Tahoe Basin, and the ambient concentration of PM2.5 is highly dependent on meteorological conditions such as wind speed and mixing conditions.
Delivering and Measuring Success

EIP Indicators

  • Miles of Street Sweeping

    Since 2009 EIP partners have swept more than 61,000 miles of roadways within the Tahoe Basin reducing fine sediment particles from roadways entering the air and water.

  • Non-Compliant Wood Stoves Removed or Retrofitted

    This EIP performance measure tracks removal of polluting wood stoves to reduce local air pollution for human and ecosystem health.

Example EIP Projects

Monitoring Programs

Rationale Details
The highest 3 Yr Avg. 98% 24 Hr from each site was evaluated against the threshold standard. In 2019, the highest reading from any site was 21.1 ug/m3 taken at the Lake Tahoe CC site. The value is 60% of the maximum allowable 35 ug/m3. Therefore, the status was considered to considerably better than target.
Trend was determined using the maximum 24-hr reading at the DL Bliss State Park site from 1991-2018 using the Theil-Sen robust regression method. An annual 3.1% increase was observed during this time frame. Therefore, a trend of rapid decline was determined. The monitor at DL Bliss State Park was not operational for much of 2019 and data were not included.
Confidence Details
High. Monitoring was conducted using strict protocols.
High. A long-term, high-quality data set is available to analyze trend.
High.
Additional Figures and Resources

No photos available.

No documents available.