Indicator
Highest 24-Hour PM10 Concentration
2023 Evaluation
View in Threshold Dashboard

PM10 describes inhalable particles, with diameters that are generally 10 micrometers and smaller. This indicator measures the highest monitored PM10 concentration averaged over every 24-hours for the calendar year. Small particulate matter can lodge in the lungs and cause or aggravate the effects of asthma, lung diseases, and heart disease. Elevated concentrations of PM10 can reduce regional visibility. On an annual basis the sources of PM10 in the Tahoe Basin include motor vehicle emissions, paved and unpaved road dust, wood smoke, wildfire smoke, and construction dust. The highest 24-hour PM10 concentrations in the region are generally associated with wildfires. PM10 is monitored by TRPA and partners at three sites around the Basin. 

Highest 24-Hour Average Pm10 Concentration.jpg
Status

Annual maximum 24-hr average PM10 in the Tahoe Region.

Data provided by the Desert Research Institute. Access detailed datasets on Tahoe Open Data, including:: Air Quality Station Location Data. Daily Monitoring Data. Yearly Average Data.

2023 Evaluation
See how thresholds are evaluated
Status
Considerably Better Than Target
Trend
Rapid Decline
Confidence
Moderate
Applicable Standard
AQ9: Particulate Matter10 24-hour Standard: Maintain Particulate Matter10 at or below 50µg/m3 measured over a 24-hour period in the portion of the Region within California, and maintain Particulate Matter10 at or below 150 µg/m3 measured over a 24-hour period in the portion of the Region within Nevada. Particulate Matter10 measurements shall be made 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
  • Average annual concentrations of PM10 in Lake Tahoe continue to improve, but peak annual concentrations have increased in years when wildfire smoke impacts the Region.
  • Improving air quality, expect during periods of wildfire is a trend that has been documented elsewhere (McClure et al 2018).
  • The highest 24- hour PM10 threshold was exceeded the standard in 2020, 2021, and 2022, when wildfire impacted the Region. The standard was in attainment in 2023 when the region was not impacted as much by wildfire smoke.
  • Increasing smoke from wildfires continues to impact the air quality in the Basin. Maximum daily PM10 concentrations are highly variable year to year depending on regional wildfire activity. See wildfire events effecting the Lake Tahoe air basin at the Climate Resilience Dashboard. 
  • The best scenario for air quality on a local, regional, and national scale is the restoration of the natural fire cycle through prescribed fire or managing natural ignitions when conditions are favorable (Schweizer et al. 2019)
  • An additional EPA standard for Highest 24 - Hour PM10 is not to be exceeded over 150 µg/m3 more than once per year on average over a 3-year period is presented as an attachment at the bottom of this indicator page.  This standard has not been met over the last monitoring period. The 3-year rolling average of exceedances has been greater than 1 for each year of this monitoring period.
Evaluation Map
Description

The location of air quality monitoring stations in the Lake Tahoe Basin. PM10 is monitored by TRPA and partners at three of these locations.

About the Threshold
This indicator measures the highest monitored PM10 concentration averaged over every 24-hours for the calendar year. Particulate matter in high concentrations less than or equal to 10 microns in size can lodge in the lungs and cause or aggravate the effects of asthma, lung diseases, and heart disease. Elevated concentrations of PM10 have also been attributed to reductions in regional visibility and increased regional haze. Federal and state standards with varying time averaging periods have been adopted to protect human health and regional visibility.
Particulate matter pollution consists of very small liquid and solid particles in the air. The primary sources of PM10 in the Lake Tahoe Basin are motor vehicle emissions, paved and unpaved road dust, wood smoke, wildfire smoke, and construction dust. The ambient concentration of PM10 is highly dependent on meteorological conditions such as wind speed and mixing conditions.
Delivering and Measuring Success

EIP Action Priorities

  • Build and Enhance Trail Networks

    Bicycling, walking, and other forms of active transportation are important methods of travel that promote healthy lifestyles, improve air quality.

  • Build and Enhance Transit Systems

    Comprehensive and coordinated bus and shuttle transit system that provides seamless around the lake service.

  • Implement Prescribed Fire

    Prescribed fire and fire used for ecological benefit can reduce smoke exposure from large high intensity fires.

  • Reduce Hazardous Fuels

    Reduce hazardous fuels and proactively manage forests to improve ecosystem resilience and reduce wildfire smoke.

EIP Indicators

  • Acres of Forest Fuels Reduction Treatment

    EIP partners have collectively treated over 94,000 acres of forest to reduce hazardous fuels and continue to treat lands in the wildland urban interface to reduce wildfire threat.

  • Miles of Street Sweeping

    Since 2009 EIP partners have swept more than 91,000 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

    Improvements in average visibility is mostly attributed to reductions in smoke from programs such as the movement to cleaner-burning wood stoves.

Example EIP Projects

Local and Regional Plans

Monitoring Programs

Rationale Details
Considerably Better Than Target. The method for status determination follows State and Federal guidelines for assessing compliance with the 24-hour PM10 standard. Sites are assessed as in attainment if there is not more than one exceedance per year averaged over three years.
The analysis was conducted with and without including data from periods influenced by exceptional events. Exceptional events are natural or unusual events that can overwhelm existing strategies designed to control man-made pollution, such as wildfires. If such an event occurs, data that would cause an exceedance of a standard was excluded when determining compliance with that standard.
The data was analyzed both with and without the inclusion of days influenced by wildfire. Days where air quality was impacted by wildfire are listed on the “Fire Dates” tab of the spreadsheet below. Including all days there were 8 days between 2000-2023 that exceeded the federal standard of 150µg/m3, and 37 days that exceeded the California standard of 50µg/m3. Removing the exceedances that were the result of wildfires, there were no exceedances of the federal standard and a single exceedance of the California standard. The three average number of exceedances during every year of the four-year evaluation period was less than 0.4, relative to a standard of one, so that status is significantly better than the target.
Rapid Decline. Trend was determined using the maximum 24-hr reading at all sites. There is an increase of 3.32% compared to the standard, therefore, the trend is considered rapid decline.
Confidence Details
High. Monitoring was conducted using strict protocols to collect a long-term, high quality dataset.
Moderate. Confidence of trend is based on the coefficient of determination and t-test significance. R²=0.7, p-value= 0.010064219.
Moderate. If one confidence rating is high and the other is moderate, the overall confidence rating is the lower confidence rating.
Additional Figures and Resources

No photos available.

Air Quality Exceedances with Exceptional Events
Uploaded On
1/17/2025
File Type
Excel (XLSX)
Description
This document includes sheets for PM2.5, PM10, O3, and exceptional event dates. It shows exceedance values and processed values with and without exceptional events, as well as relevant Threshold Standards . Columns ending in "_exempt" exclude exceptional events, while "_all" includes all dates.
PM 10 - 24Hr High- 3 Yr Rolling Average of Exceedances
Uploaded On
11/14/2024
File Type
Excel (XLSX)
Description
This document contains a chart and table of data showing 3- year rolling averages of exceedances. One exceedance per year on average over three years is the Threshold used to assess attainment.