Indicator
Highest 8-Hour Average Concentration of Carbon Monoxide
2019 Evaluation
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This indicator addresses the highest carbon monoxide concentrations averaged over every eight hours for the calendar year. 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. 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. 

 

Highest 8-Hour Average Concentration Of Carbon Monoxide.jpg
Status

Highest annual maximum 8-hour concentration of carbon monoxide in the Tahoe Basin from 1980 to present.

Desert Research Institute

2019 Evaluation
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Status
Considerably Better Than Target
Trend
Moderate Improvement
Confidence
High
Applicable Standard
AQ1: Maintain carbon monoxide concentrations at or below 6 parts per million (7 mg/m3) averaged over 8 hours.
Key Points
  • Peak carbon monoxide levels decreased substantially in South Lake Tahoe since the 1980's mostly due to cleaner car engines.
  • 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.
Evaluation Map
Description

A map displaying current air quality monitoring stations within the Tahoe Basin. Carbon monoxide is monitored at the Stateline, Nevada station.

About the Threshold
Carbon monoxide (CO) in high concentrations affects human health by reducing the supply of oxygen to the tissues of the body. Health effects can include headaches, nausea, reduced mental alertness and even death, at very high concentrations. TRPA, federal and state standards have been adopted to protect the public from this harmful pollutant. This indicator addresses the highest CO concentrations averaged over every 8-hours for 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.

EIP Indicators

Example EIP Projects

Local and Regional Plans

Monitoring Programs

Rationale Details
The current status was determined based on the maximum 8-hour reading taken in 2019 at the TRPA Stateline monitoring station, the most recent year monitoring data is available. The reading was 4.5 ppm which is 75% of the maximum allowed value. Therefore, it is considerably better than the target.
Trend was determined using the Theil-sen robust linear regression from the readings taken at the Stateline casinos from 1983-2012. During this time, CO levels decreased by an average of 1.6% per year and is therefore considered moderate improvement. Monitoring at the casinos was stopped in 2012 due to continued readings well within applicable standards.

Readings at the TRPA building in Stateline started in 2013. These are not included in the trend analysis because they are not comparable to the casino sites due to being much further from Highway 50.
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.
High. Monitoring data from the Stateline casinos was conducted using standardized protocols and shows a clear decreasing trend.
High.
Additional Figures and Resources

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