Highest 8-Hour Average Concentration of Carbon Monoxide
Carbon monoxide (CO) is a tasteless, odorless, and colorless gas. It is a public health concern because elevated concentrations affect human and animal health by reducing the supply of oxygen to body tissues. This indicator measures the highest carbon monoxide concentration averaged over eight hours for the calendar year. The primary anthropogenic sources of CO in the Tahoe Region are on-road motor vehicles, residential wood burning, motorized watercraft, and off-highway vehicles. Wildfires are a natural source of CO. Policy and management actions implemented through the Regional Plan to control CO emissions focus on reducing private automobile use through improvements to public transportation and bike/pedestrian trail infrastructure. Vehicle emission standards enacted by state and federal governments also reduce CO emissions in the Region, mainly by requiring improvements in engine and exhaust technologies. Several sites have monitored CO through the years, and TRPA currently monitors CO at the Stateline, Nevada location.
Status
Highest annual maximum 8-hour concentration of carbon monoxide in the Tahoe Basin from 1980 to present. Note there are two trend lines as a separate trend line was created once the station was relocated to the TRPA building at Stateline, Nevada.
Data provided by the Desert Research Institute. Access detailed datasets on Tahoe Open Data, including: Air Quality Station Location Data, Daily Monitoring Data, and Yearly Average Data.
Evaluation Map
A map displaying current air quality monitoring stations within the Tahoe Basin. Carbon monoxide is monitored at the Stateline, Nevada station.
2023 Evaluation
- Status
- Considerably Better Than Target
- Trend
- Moderate Decline
- Confidence
- Moderate
Applicable Standard
AQ1: Maintain carbon monoxide concentrations at or below 6 parts per million (7 mg/m3) averaged over 8 hours.
Key Points
- Carbon Monoxide concentrations have been consistently below all applicable standards, except for one day during the 2021 Caldor Fire period when the Stateline site recorded 8-hr CO greater than the California state standard.
- Climate change-driven warming and an overstocked forest will likely lead to more frequent and intense wildfires that could result in more frequent standard exceedance (Indicators of Climate Change in California, 2022).
- Peak carbon monoxide levels have decreased substantially in South Lake Tahoe since the 1980's except during periods impacted by wildfire. See wildfire events effecting the Lake Tahoe air basin at the Climate Resilience Dashboard.
- Carbon monoxide levels have dropped to levels where the Environmental Protection Agency and the Nevada Department of Environmental Protection consider the Tahoe Basin to be in attainment; therefore, they no longer actively monitor carbon monoxide.
- TRPA added a carbon monoxide monitor in 2012 and has found levels to be consistently far below acceptable levels.
About the Threshold
- High concentrations of carbon monoxide (CO) impact human health by reducing the supply of oxygen to the body's tissues. Health effects can include headaches, nausea, reduced mental alertness, and even death. TRPA, federal, and state standards have been adopted to protect the public from this harmful pollutant. This indicator measures the highest 8-hour CO concentration during the calendar year.
- Carbon monoxide is emitted from incomplete fuel combustion by sources such as cars, trucks, boats, construction equipment, fireplaces, woodstoves, furnaces, and wildfire. The ambient concentration of CO is highly dependent on meteorological conditions such as temperature, 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, boost the local economy, and enhance community.
-
Build and Enhance Transit Systems
Comprehensive and coordinated bus and shuttle transit system that provides seamless around the lake service.
-
Reduce Hazardous Fuels
Reduce hazardous fuels and proactively manage forests to improve ecosystem resilience.
EIP Indicators
-
Miles of Pedestrian and Bicycle Routes Improved or Constructed
Since 1997 EIP partners have collectively constructed or improved 198 miles of pedestrian and bicycle routes reducing the number of vehicle trips.
-
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
-
South Tahoe Greenway Shared Use Trail Phases 1b & 2
This project completed in 2022 expands on the existing bicycle network and connections in South Lake Tahoe.
Local and Regional Plans
-
Climate Adaptation Action Portfolio
Reducing emissions improves air quality.
-
Tahoe Climate Resilience Action Strategy 2022
Addressing emissions is core climate resilience strategy.
-
Tahoe-Truckee Plug-in Electric Vehicle Readiness Plan
This plan focuses on infrastructure for plug-in electric vehicles within the Tahoe-Truckee Region because they play a critical role in reducing the GHG emissions of vehicles.
Monitoring Programs
Rationale Details
- Considerably Better Than Target. The current status was determined based on the average during the evaluation period (2020-2023). The average over the four years was 2.8ppm. During the evacuation period for the Caldor fire in 2021, an 8-hour concentration of 6.9 was observed. The four-year average was less than half the threshold standard even when the Caldor fire measurement was included. Non-fire impacted average was less than a third of the threshold standard. Therefore, it is considerably better than the target.
- Moderate Decline. Trend was determined using the Theil-sen robust linear regression from the readings taken at the Stateline TRPA office from 2013- 2023. During this time, CO levels increased by an average of 2.1% per year and is therefore considered a moderate decline. Monitoring at the casinos was stopped in 2012 due to continued levels well below applicable standards and was no longer seen as a priority by the Environmental Protection Agency and the Nevada Department of Environmental Protection. Readings at the TRPA building in Stateline started in 2013.
Confidence Details
- High. While the current monitoring of CO at the TRPA building in Stateline likely does not capture maximum CO levels because of its distance from Highway 50, TRPA is confident CO levels are below applicable standards. Readings prior to 2012 at Harveys in Stateline were consistently below applicable standards, and traffic levels that would cause an increase in CO have not increased to levels seen in 2012.
- Low. Confidence of trend is based on the coefficient of determination and t-test significance. R²=0.12 (low) and t-test significance, p-value= 0.3 (moderate)
- Medium. If one confidence rating is high and the other is low, the overall confidence rating is medium.
Additional Figures and Resources
No photos available.
- Uploaded On
- 11/13/2024
- File Type
- Description
- This fourth edition of the Indicators of Climate Change in California report continues to track changes in the state’s climate and its impacts in the state.