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Home Air Greenhouse Gases

PM10 24 Hour Average Concentration

Status and Trend

Interpretation and Commentary

Somewhat Worse Than Target
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Status: Somewhat Worse Than Target
Trend: Moderate Improvement
Confidence: Moderate

  • Relevance - Particulate matter less than or equal to 10 microns in size (PM10) in high concentrations can lodge in the lungs and can cause or aggravate the effects of asthma, lung diseases and heart disease. TRPA, federal and state standards, with varying time averaging periods, have been adopted to protect the public from this harmful pollutant. This indicator addresses the highest monitored PM10 concentration averaged over every 24 hours for the calendar year.
  • Condition Status – The highest 24 hr avg. PM10 concentration monitored in 2009 was 52.8 µg/m3.1 This value is equal to 106% of the most stringent (CA) standard of 50µg/m3. A condition status of “slightly worse than target” is therefore designated.
  • Trend – Trends were calculated using the Thiel regression method which is academically well accepted for air quality analysis.
    • Long Term Trends - The long term trend is indicated by the arrow in the reporting icon above. There is a long term trend between 1993 and 2009 of decreasing values of the highest 24 hour PM10 concentrations at the South Lake Tahoe site. The graph above illustrates a long term change in concentration of -1.1 µg/m3-yr. This change is equal to -2.2% per year of the most stringent (CA) standard of 50 µg/m3 so the trend designation is “moderate improvement”.
    • 5 Year Trend - The trend in the most recent 5 years (2005-2009) is not consistent with the long term trend and indicates an increase in highest 24 hour PM10 concentrations of 8.1 µg/m3-yr.,or +16.2% per year of the standard. Note that short term trends in air quality are typically not reliable due to the variability of meteorology from one year to the next. 

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  • Confidence
    • Condition Status - There is high confidence in the condition status because the data is collected using federal reference methods2, is subject to extensive quality assurance requirements and was collected recently.
    • Long Term Trends - The confidence in the long term trend for the analysis of 17 data points of the 24 hr avg.PM10 concentration is moderate with a confidence level of 73%. a S value of -17 and a P value of 0.27.
    • 5 Year Trend - The confidence in trend for the most recent 5 years (2005-2009) is moderate with a confidence level of 60%, a S value of 2 and a P value of 0.4.
    •  Overall Confidence - The overall confidence in the status and trend is represented by the border in the reporting icon above and is moderate because the moderate confidence in the long-term and short-term trends outweigh the high confidence in the condition status.
  • Human and Environmental Drivers - 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 vehicles, paved and unpaved road dust, wood smoke, and construction dust.The ambient concentration of PM10 is highly dependent on meteorological conditions such as wind speed and mixing conditions.
  • Monitoring Approach – PM10 is monitored at one location in the Lake Tahoe Basin, located on Sandy Way in South Lake Tahoe. Data is collected, analyzed and reported by the California Air Resources Board.1
  • Monitoring Partners– California Air Resources Board,  U.S. Environmental Protection Agency, and Tahoe Regional Planning Agency


  • Monitoring Plan
  • Conceptual Model


PM10 Monitoring Locations in the Lake Tahoe Basin

click map for larger image

Trend Charts

The highest 24-hour-average particulate matter less than or equal to 10 microns in size (PM10) concentration in the Lake Tahoe Basin. Concentrations are all better than the federal and Nevada standards, but slightly worse than the California standard. The long-term trend at South Lake Tahoe site shows moderate improvement over the entire period of record from 1989 through 2009.
Source: U.S. Environmental Protection Agency, Air Data
Nevada Division of Environmental Protection

Additional Info


  1. California Air Resources Board website, April 26, 2011:http://www.arb.ca.gov/adam/.
  2. U.S. EPA methods for air quality monitoring: http://www.epa.gov/ttn/amtic/files/ambient/criteria/reference-equivalent-methods-list.pdf

Additional Information

  1. PM10 Annual Avg. Indicator
  2. CARB fact sheet on health effects: http://www.arb.ca.gov/html/fslist.htm#Health
  3. Conceptual Model: A conceptual model for Air Quality CO does not exist as of June 2011 and is anticipated to be developed in 2011.
  4. Monitoring Plan: A monitoring plan for Air Quality CO does not exist as of June 2011 and is anticipated to be developed in 2012
Last Updated on Tuesday, 16 October 2012 13:16